The rhizosphere

The rhizosphere is a zone in the soil that is influenced by roots. Living roots change the atmosphere around them by using up oxygen and producing carbon dioxide (see respiration p118). Roots exude a variety of organic compounds that hold water and form a coating that bridges the gap between root and nearby soil particles. Micro-organisms occur in greatly increased numbers and are more active in proximity to roots. Some actually invade the root cells where they live as symbionts. The Rhizobium...

Garden Chafer Phyllopertha horticola

This pest is increasingly proving a problem on turf where the large white grubs eat the roots. Small yellow patches appear in the lawn or sports area, notably in summer when the grubs are becoming fully grown. Further damage can occur when starlings, crows, moles, foxes and even badgers dig up parts of the lawn to reach the succulent prey. Life cycle. The adult is a broad, 1 cm long, light-brown beetle with a bottle-green upper thorax and head. Adults emerge from soil-borne pupae in May...

Living organisms in the soil

As in any other plant and animal community the organisms that live in the soil form part of the food webs (see p53). The main types present in any soil are the primary producers which are those capable of utilizing the sun's energy directly, synthesizing their own food by photosynthesis, such as green plants (see photosynthesis), the primary consumers which are those organisms which feed directly on plant material, and secondary consumers which feed only on animal material. In practice, there...

Green manures

Unlike leys, green manuring is the practice of growing a cover crop primarily to incorporate in the soil. It is undertaken to provide organic matter which can improve soil structure, aeration, water-holding capacity and, on decomposition, increase microorganism activity in the soil add some nutrients, especially nitrogen (depending on the plants involved), for the following crop take up and store nitrogen that would otherwise be leached from bare soil over the winter period deep rooted plants...

Removal of dead flowers

Length Xanthrophyll

The removal of dead flowers, an activity called dead-heading, is an effective way to help maintain the appearance of a garden border. Examples of species needing this procedure are seen in bedding plants which flower over several months, e.g. African Marigold (Tagetes erecta) in herbaceous perennials, e.g. Delphinium and Lupin in small shrubs, e.g. Penstemon fruticosus and in climbers, e.g. sweet pea and Rosa 'Pink Perpetue'. As flowers age, they begin to use up a considerable amount of the...

Lime application

Unless very coarse grades are used, lime raises the soil pH over a one-to two-year period, although the full effect may take as long as four years thereafter pH falls again. Consequently lime application should be planned in the planting programme. It is normally worked into the top 15 cm of soil. If deeper incorporation is required, the quantity used should be increased proportionally. The lime should be evenly spread and regular moderate dressings are preferable to large infrequent...

Mulching

Many organic materials are used as mulches including farmyard manure, leaf mould, bark, compost, lawn clippings and spent mushroom compost. Organic mulches increase earthworm activity at the surface, which promotes better and more stable soil structure in the top layers. Soil compaction by water droplets is reduced and, as the organic mulches are incorporated, the soil structure can be improved. If thick enough mulches can suppress weed growth, but it is counter-productive to introduce a...

Water uptake

The movement of water into the roots is by a special type of diffusion called osmosis. Soil water enters root cells through the cell wall and membrane. Whereas the cell wall is permeable to both soil water and the dissolved inorganic minerals, the cell membrane is permeable to water, but allows only the smallest molecules to pass through, somewhat like a sieve. Therefore the cell membrane is considered to be a partially permeable membrane. A greater concentration of minerals is usually...

Artificial methods of propagation

The artificial methods of vegetative propagation encompass most organs of the plant. Cuttings are parts of plants that have been carefully cut away from the parent plant, and which are then used to produce a new plant. Many species can be propagated in this way. Different methods may be necessary for different species. Only healthy parent plants should be used. Hygienic use of knives, compost and containers is strongly recommended. Cuttings are normally taken from parts of the plant exhibiting...

Addition of organic matter

It is normal in horticulture to return plant residues to cultivated areas where possible. Whether or not the plant remains are worked into the soil in which they have been grown depends upon their nature. The residue of some crops, such as tomatoes in the greenhouse, is removed to reduce disease carry over and because it cannot easily be incorporated into the soil. Other crops, such as hops, are removed for harvesting and some of the processed remains, spent hops, can be returned or used...

Sulphur

Sulphur taken up as sulphate ions is a nutrient required in large quantities for satisfactory plant growth. It is not normally added specifically as a fertilizer because the soil reserves are replenished by re-circulated organic matter and a steady supply from winds off the sea in the form of dimethyl sulphide (DMS) that gives the distinctive smell of the seaside. Air pollution has added considerably to the supply reaching the land. Several fertilizers used to add other nutrients are in...

Greenhouse mealy bug Planococcus citri

This pest, a distant relative of the aphid, spoils the appearance of glasshouse crops, particularly orchids, Coleus species, cacti and Solanum species. All of the stages except the egg suck phloem juices by means of a tubular mouthpart (stylet), and when this pest is present in dense masses it produces honey dew and may cause leaf drop (see Figure 14.11). Figure 14.11 (a) Mealy bug (b) Brown scale Figure 14.11 (a) Mealy bug (b) Brown scale Life cycle. Being a tropical species, it...

Application methods

Fertilizers are applied in several different ways. Base dressings are those that are incorporated in the growing medium. Combine drilling with seeds and fertilizer running into the same drill can achieve this. In horticulture, however, band placement of fertilizers is far more common, involving equipment that drills the seeds in rows and places a band of fertilizer in parallel a few centimetres below and to one side. The risk of retarded germination Table 21.3 Sources of nutrients for use in...

Single species communities

When a plant community is made up of one species it is referred to as a monoculture. Most fields of vegetables such as carrots have a single species in them. On a football field there may be only ryegrass (Lolium) with all plants a few millimetres apart. Each plant species, whether growing in the wild or in the garden, may be considered in terms of its own characteristic spacing distance (or plant density). For example, in a decorative border, the bedding plant Alyssum will be planted at 15 cm...

Further classifications of plants

Plants can be grouped into other useful categories. A classification based on their life cycle (ephemerals, annuals, biennials and perennials) has long been used by growers, who also distinguish between the different woody plants such as trees and shrubs. Growers distinguish between those plants that are able to withstand a frost (hardy) and those that cannot (tender) plants can be grouped according to their degree of hardiness. Table 4.4 brings together these useful terms, provides some...

Preface

By studying the principles of horticulture, one is able to learn how and why plants grow and develop. In this way, horticulturists are better able to understand the responses of the plant to various conditions, and therefore to perform their function more efficiently. They are able to manipulate the plant so that they achieve their own particular requirements of maximum yield and or quality at the correct time. The text therefore introduces the plant in its own right, and explains how a correct...

Warm water treatment

This method is used for pests such as stem and bulb nematodes in narcissus bulbs. Immersion of bulbs for 2 hours at 44 C controls the pest without seriously affecting bulb tissues. Chrysanthemum stools and strawberry runners may be similarly treated, using temperature and time combinations favourable to each crop. Viruses (such as aspermy virus on chrysanthemum) are more difficult to control, since viruses are more intimately associated with the plant nuclei. Virus concentrations may be greatly...

Loamless or soilless composts

Loamless composts introduced the advantages of a uniform growing medium, but with components that are lighter, cleaner to handle, cheaper to prepare and which do not need to be sterilized (unless being used more than once). Many have low nutrient levels which enable growers to manipulate plant growth more precisely through nutrition, but the control of nutrients is more critical, as many components have a low buffering capacity. Peat has until recently been the basis of most loamless composts....

Fertilizers

Straight fertilizers are those that supply only one of the major nutrients nitrogen, phosphorus, potassium or magnesium (see Table 21.2). The amount of nutrient in the fertilizer is expressed as a percentage. Nitrogen fertilizers are described in terms of percentage of the element nitrogen in the fertilizer, i.e. per cent N. Phosphate fertilizers have been described in terms of the equivalent amount of phosphoric oxide, i.e. per cent P2O5, or increasingly as percentage phosphorus, per cent P....

Other mites

Four other horticulturally important mites require a mention. The fruit tree red spider mite Panonychus ulmi causes serious leaf mottling of ornamental Malus and apple. Conifer spinning mite Oligonychus ununguis causes spruce leaves to yellow, and the mite spins a web of silk threads. Bulb-scale mite Steneotarsonemus laticeps causes internal discoloration of forced narcissus bulbs. Bryobia mite e.g. Bryobia rubrioculus attacks fruit trees, and may cause damage to greenhouse crops, e.g....

Algae and lichens

Food Delicacies Florence

The algae, comprising some 18000 species, are true plants, since they use chlorophyll to photosynthesize see Chapter 8 . The division Chlorophyta green algae contains single-celled organisms that require water for reproduction and can present problems when blocking irrigation lines and clogging water tanks. Marine algal species in Phaeophyta brown algae and Rhodophyta red algae are multicellular, and have leaf-like structures. They include the seaweeds, which accumulate mineral nutrients, and...

Hydroponics

Hydroponics water culture involves the growing of plants in water. The term often includes the growing of plants in solid rooting medium watered with a complete nutrient solution, which is more accurately called 'aggregate culture'. Plants can be grown in nutrient solutions with no solid material so long as the roots receive oxygen and suitable anchorage and support is provided. The advantages of hydroponics, compared with soil, in temperate areas includes accurate control of the nutrition of...

Air drainage

Cold Air Drainage

Cold air tends to fall, because it is denser than warm air, and collects at the bottom of slopes such as in valleys. Frost pockets occur where cold air collects plants in such areas are more likely to experience frosts than those on similar land around them. This is why orchards, where blossom is vulnerable to frost damage, are established on the slopes away from the valley floor. Cold air can also collect in hollows on the way down slopes. It can also develop as a result of barriers, such as...

The effects of specific abiotic factors pollutants on plants

Penny Covered Table Top

Continuing increase in soil acidity reduces vital mycorrhizal activity, causes leaching of nutrients such as magnesium and calcium, and leaves phosphate in an insoluble form. In soils formed over limestone and chalk, the effects of acid rain are much less damaging. Excess nutrient levels in water and soils especially from fertilizers and farm silage encourage increase in algae and a corresponding loss of dissolved oxygen. This process called eutrophication has a serious effect on plant...

World climates

Rainfall Distribution British Isles

In addition to maritime and continental climates already mentioned there are many others, including the Mediterranean climate as found in southern parts of Europe, California, South Africa, Australia and central Chile that is typified by hot dry summers and mild winters. The characteristics of a range of the world climate types are given in Table 2.4 . Plants native to these other areas can present a challenge for those wishing to grow them in the British Isles. To some extent plants are...

Pollution

Gases in the air, which are usually products of industrial processes or burning fuels, can cause damage to plants, often resulting in scorching symptoms of the leaves. Fluoride can accumulate in composts and be present in tap water, so causing marginal and tip scorch in leaves of susceptible species such as Dracaena and Gladiolus. Sulphur dioxide and carbon dioxide may be produced by faulty heat exchangers in glasshouse burners, especially those using paraffin. Scorch damage over the whole leaf...

Particle size classes

Sand Silt And Clay Comparison

There is a continuous range of particle sizes, but it is convenient to divide them into classes. Three major classification systems in use today are those of the International Society of Soil Science ISSS , United States Department of Agriculture USDA and the Soil Survey of England and Wales SSEW . These are illustrated in Figures 17.8 and 17.9. In this text the SSEW scale used by the Agricultural Development and Advisory Service of England and Wales ADAS is adopted. In each case, soil is...

Barriers

A physical barrier such as a fence sunk into the ground deters rabbits and deer. Fine screens placed over ventilation fans help prevent the entry of pests, such as fungus gnats, from outside a greenhouse or mushroom house. Pots placed on small stands in water-filled trays are freed from the visitations of red spider mite and adult vine weevils. Peach leaf curl is a difficult disease to control. A plastic sheet placed over the peach or almond over winter will greatly reduce both arrival of...

Some important horticultural weeds

Seedling Chickweed

Specific descriptions of identification, damage, biology and control measures are given for each weed species. Detailed discussion of weed control measures cultural, chemical and legislative is presented in Chapter 16. Chickweed Stellaria media . Plant family - Caryophyllaceae Damage. This species is found in many horticultural situations as a weed of flowerbeds, vegetables, soft fruit and greenhouse plantings. It has a wide distribution throughout Britain, grows on land up to altitudes of 700...

Movement of heat and weather systems

World Wind Circulation System

Heat energy moves from warmer areas i.e. those at a higher temperature into cooler areas i.e. those at a lower temperature and there are three types of energy movement involved. Radiation energy moves efficiently through air or a vacuum , but not through water or solids. Heat is transferred from the Earth's surface to the lower layers by conduction. As soil surfaces warm up in the spring, temperatures in the lower layers lag behind, but this is reversed in the autumn as the surface cools and...

Chapter Plant development

Photoperiodism Flower Pictures

This chapter includes the following Figure 11.1 Autumn colour in the leaves of Parthenocissus tricuspida Boston Ivy , developing in response to environmental changes Figure 11.1 Autumn colour in the leaves of Parthenocissus tricuspida Boston Ivy , developing in response to environmental changes

Liming materials

Burn Calcium Carbonate

Liming materials can be compared by considering their ability to neutralize soil acidity, fineness, and cost to deliver and spread. The neutralizing value NV of a lime indicates its power to overcome acidity. A neutralizing value of 50 signifies that 100 kg of that material has the same effect on soil acidity as 50 kg of calcium oxide. The fineness of the lime is important because it indicates the rate at which it affects the soil acidity see surface area p304 . It is expressed, where relevant,...

Horticulture Shoot Axil

The stem's function is physically to support the leaves and flowers, and to transport water, minerals and food between roots, leaves and flowers see p91 for stem structure . The leaf joins the stem at the node and has in its angle axil with the stem an axillary bud, which may grow out to produce a lateral shoot. The distance between one node and the next is termed the internode. In order to perform these functions, the stem produces tissues see Chapter 6 specially formed for efficiency. It must...

Acknowledgements

We are indebted to the following people without whom the new edition would not have been possible The dahlia featured on the cover is 'Western Spanish Dancer' and is with the kind permission of Aylett Nurseries Ltd. Nick Blakemore provided the microscope photographs used on the cover and through the plant section of the new edition. Thanks are also due to the following individuals, firms and organizations that provided photographs and tables Agricultural Lime Producers' Association Dr C.C....

Topography

North Facing Slope Sunlight

The presence of slopes modifies climate by its aspect and its effect on air drainage. Aspect is the combination of the slope and the direction that it faces. North-facing slopes offer plants less sunlight than a south-facing one. This is dramatically illustrated when observing the snow on opposite sides of an east- west valley or roofs in a street , when the north facing sides are left white long after the snow has melted on the other side see Figure 2.9 much Figure 2.9 Effect of aspect note...

Arabis mosaic

Reversion Virus Blackcuirrant

This virus infects a wide range of horticultural crops. On strawberries, yellow spots or mottling are produced on the leaves, and certain cultivars become severely stunted. On ornamental plants, e.g. Daphne odorata, yellow rings and lines are seen on infected leaves, and the plants may slowly die back, particularly when this virus is associated with cucumber mosaic inside the plant. Life cycle. Several weeds, e.g. chickweed and grass spp., may harbour this disease, and in strawberries...

Mixed weed populations

Dock Plant Weed

In the field a wide variety of both annual and perennial weeds may occur together. The horticulturalist must recognize the most important weeds in their holding or garden, so that a decision on the precise use of chemical control with the correct herbicide is achieved. Particular care is required to match the concentration of the herbicide to the weed species present. Also, the grower must be aware that continued use of one chemical may induce a change in weed species, some of which may be...

Roots

The function of the root system is to take up water and mineral nutrients from the growing medium and to anchor the plant in that medium. Its major function involves making contact with the water in the growing medium. To achieve this it must have as large a surface area as possible. The root surface near to the tip where growth occurs cell division in the meristem, see p93 is protected by the root cap. The root zone behind the root tip has tiny projections...

Hygienic growing

During the crop, the grower should aim to provide optimum conditions for growth. Water content of soil should be adequate for growth see field capacity , but not so excessive that root diseases such as damping off in pot plants, club root of cabbage and brown root rot of conifers are actively encouraged. Water sources can be analyzed for Pythium and Phytophthora species if damping off diseases are a constant problem. Covering and regular cleaning of water tanks to prevent the breeding of these...

Fungi

Downy Mildew Fruiting Body

Some fungi are single celled such as yeasts but others are multicellular, such as the moulds and the more familiar mushrooms Figure 4.10 Fungi showing fruiting bodies Figure 4.10 Fungi showing fruiting bodies and toadstools. Most are made up of a mycelium, which is a mass of thread-like filaments hyphae . Their cell walls are made of chitin. Their energy and supply of organic molecules are obtained from other organisms heterotrophic nutrition . They achieve this by secreting digestive enzymes...

Animals

The animal kingdom includes a very large number of species that have a significant influence on horticulture mainly as pests see Chapter 14 or as contributors to the recycling of organic matter see Chapter 18 . Some of the most familiar animals are in the phylum Chordata that includes mammals, birds, fish, reptiles and amphibians. Mammal pest species include moles see p200 , rabbits see p198 , deer, rats and mice. Bird pest species are numerous including pigeons and bullfinches, but there are...

Organic growing

The organic movement broadly believes that crops and ornamental plants should be produced with as little disturbance as possible to the balance of microscopic and larger organisms present in the soil and also in the above-soil zone. This stance can be seen as closely allied to the conservation position, but with the difference that the emphasis here is on the balance of micro-organisms. Organic growers maintain soil fertility by the incorporation of animal manures, or green manure crops such as...

Further reading

Crop Nutrition andFertilizer Uses. 2nd edn. Farming Press. Brown, L.V. 2008 . AppliedPrinciples ofHorticultural Science. 3rd edn. B utterworth-Heinemann. Cresser, M.S. et al. 1993 . Soil Chemistry and Its Applications. CUP Hay, R.K.M. 1981 . ChemistryforAgriculture andEcology. Blackwell Scientific Publications. Ingram, D.S. et al. eds . 2002 . Science and the Garden. Blackwell Science Ltd. Pratt, M. 2005 . Practical Sciencefor Gardeners. Timber Press. Simpson, K. 1986 ....

Plant modifications to extreme conditions see also p

A survey of plants worldwide shows what impressive structural and physiological modifications they possess to survive in demanding habitats. A few examples of British species are described here. Marram grass Ammophila arenaria living on sand dunes controls water-loss by means of leaf lamina which in cross-section is shown to be rolled up. It also possesses extremely long roots see page 78 . The yellow water lily Nupar lutea shows the following modifications leaves with a thin cuticle but with...

Sowing in the open

The success of sowing outdoors depends greatly on preparing the seedbed the tilth needs to be matched to the type of seed, soil texture and the expected weather conditions see p313 . The area to be prepared should be free draining. It is thoroughly dug or ploughed depending on the scale of operation. Weeds are buried and organic matter is incorporated in the process. Ideally this is done in the autumn especially if it is a heavy soil the raw soil is then exposed to the action of frost and rain...

Cultivation

Once soil has been cultivated a distinct boundary between topsoil and subsoil is developed as the concentration of organic matter in the surface layers is evened out see Figures 18.5 and 17.5 . On first cultivation the increased aeration and nutrients stimulate micro-organisms and a new equilibrium with lower soil organic matter levels prevails. Once under cultivation grasses and high-producing legumes tend to increase organic matter levels, but most crops, particularly those in which complete...

Info

White Rot Onion

A disease is an unhealthy condition in a plant caused by a fungus, bacterium or virus. Below are described some of the most important horticultural diseases caused by fungi, bacteria and viruses. Structure and biology of fungi, bacteria and virus Fungi, commonly called moulds, cause serious losses in all areas of horticulture. They are thought to have common ancestors with the filamentous algae, a group including the present-day green slime in ponds. Some details of their classification are...

Chrysanthemum eelworm Aphelenchoidesritzemabosi

The first symptom is blotching and purpling of the leaves, which spreads and becomes a dead brown, V-shaped area between the veins. The lower leaves are worst affected. When buds are infested, the resulting leaves may be misshapen. In addition to chrysanthemum, this nematode also attacks Saintpaulia and strawberries. Life cycle. Most species of nematode live in the soil. This 1 mm long nematode spends most of its life cycle inside young leaves of the species mentioned above. The adults...

The mole [Talpa europea

Mole The Grass

The mole is found in all parts of the British Isles except Ireland. Damage. This dark-grey, 15 cm long mammal, weighing about 90 g, uses its shovel-shaped feet to create an underground system 5-20 cm deep and up to 0.25 ha in extent. The tunnel contents are excavated into mole hills see Figure 14.2 . The resulting root disturbance to grassland and other crops causes wilting, and may result in serious losses. Life cycle. In its dark environment, the solitary mole moves, actively searching for...

Cultural operations

Soil pH acidity and alkalinity levels are checked to ensure that the soil or substrate is suitable for the crop intended. If too low the appropriate amount of lime is added see p361 or if too high sulphur can be used to acidify the soil see p364 . Cultivations required in outdoor production depend on the plants, the site and the weather. Usually the soil is turned over, by digging or ploughing, to loosen it and to bury weeds and incorporate organic matter, then it is worked into a suitable...

Tulip break

The petals of infected tulips produce irregular coloured streaks and may appear distorted. Leaves may become light green, and plants become stunted after several years' infection. The virus is spread mechanically by knives, while three aphid vectors are known the bulb aphid in stores, the melon aphid in greenhouses, and the peach-potato aphid outdoors and in greenhouses. Preventative control must be used against this disease. Removal of infected plants in the field prevents a source of virus...

Damage

Broad Leaved Dock Cotyledon

Problems caused by weeds may be categorized into seven main areas Competition between the weed and the plant for water, nutrients and light may prove favourable to the weed if it is able to establish itself quickly. A large cleaver plant Galium aparine , for example, may compete for a square metre of soil. The cultivated plants are therefore deprived of their major requirement and poor growth results. The extent of this competition is largely unpredict able, varying with climatic factors such...

Irrigation plans

In general, water should not be added to outdoor soils until moisture levels fall to 50 per cent of available water content in the rooting zone. Outdoors 25 mm of water is the minimum that should be added at any one time in order to reduce the frequency of irrigation, to reduce water loss by evaporation and to prevent the development of shallow rooting. On most soils the amount of water added should be such as to return the soil to field capacity. Addition of water to clays and clay loams...

Storage

Geodeic Biome

An understanding of the physiology of the vegetable or plant material being stored is necessary to achieve the best possible results. Root vegetables are normally biennial and naturally prepared to be overwintered, whether in a store or outside see p119 . Annual vegetables are actively respiring at the time of picking see p118 , but with the correct temperature and humidity conditions the useful life can be extended considerably. Great care must be taken with all produce to be stored as any...

Bees in pollination

Horticulture Pollination

The well-known social insect, the honey bee Apis mellifera , is helpful to horticulturists. The female worker collects pollen and nectar in special pockets honey baskets on its hind legs. This is a supply of food for the hive and, in collecting it, the bee transfers pollen from plant to plant. Several crops, such as apple and pear, do not set fruit when self-pollinated. The bee therefore provides a useful function to the fruit grower. In large areas of fruit production the number of resident...

Phosphorus

Phosphorus is taken up by plants in the form of the phosphate anion H2PO43-. Phosphorus is mobile in the plant and is constantly being recycled from the older parts to the newer growing areas. In practice this means that, although seeds have rich stores of phosphorus, phosphate is needed in the seedbed to help establishment. Older plants have a very low phosphate requirement compared with quick growing plants harvested young. Most soils contain very large quantities of phosphorus, but only a...

Plant form in design

Horticultural Background Designs

Plant form as individual plants or in groups is the main interest for many in horticulture who use plants in the garden or landscape. Contrasts in plant shapes and sizes can be combined to please the eye of the observer. The dominant plant within a garden feature is usually a tree or shrub chosen for its special striking appearance, or specimen plant. In a large feature, it may be a Betula pendula silver birch tree growing up to 20 m in height with a graceful form, striking white bark, and...

Leaves

Xerophytes And Their Adaptations

The leaf, consisting of the leaf blade lamina and stalk petiole , carries out photosynthesis, its shape and arrangement on the stem depend on the water and light energy supply in the species' habitat. The arrangement of leaves and examples in different species, along with the major differences between monocotyledons and dicotyledons, is described in Chapter 4. Leaf structure, as an organ of photosynthesis, is described in Chapter 8 see p117 . The features of typical plants are given, but there...

Glasshouse whitefly Trialeurodes vaporariorum

This small insect, looking like a tiny moth, was originally introduced from the tropics, but now causes serious problems on a range of glasshouse food and flower crops. It should not be confused with the very similar, but slightly larger cabbage whitefly on brassicas. Damage. All stages after the egg have sucking stylets, which extract a sugary liquid from the phloem, often causing large amounts of honeydew and sooty moulds on the leaf surface. Plants that are seriously attacked include...

Mutations

Recombinant Dna Plant

Spontaneous changes in the content or arrangement of chromosomes mutations , whether in the cells of the vegetative plant or in the reproductive cells, occur in nature at the rate of approximately one cell in one million. These changes to the plant DNA are one of the most important causes of new alleles see p141 leading to changes in the characteristics of the individual. Extreme chromosome alterations result in malformed and useless plants, but slight rearrangements may provide horticulturally...

Identifying plants

Cruciferae Cheiranthus Cheiri

A flora is a text written for the identification of flowering plant species. Some flora use only pictures to classify plants. More detailed texts use a more systematic approach where reference is made to a key of features that, by elimination, will lead to the name of a plant. Species are described in terms of their flowers, inflorescences, stems, leaves and fruit. This description will often include details of shape, size and colour of these plant parts. Flowers. The number and arrangement of...

Fireblight Erwinia amylovora

Erwinia Amylovora Life Cycle

This disease, which first appeared in the British Isles in 1957, can cause serious damage on members of the Rosaceae family. Individual branches wilt and the leaves rapidly turn a 'burnt' chestnut brown. When the disease reaches the main trunk, it spreads to other branches and may cause death of the tree within six weeks of first infection, the general appearance resembles a burnt tree, hence the name of the disease. Badly infected plants produce a bacterial slime on the outside of the...

Brown scale Parthenolecanium corni

The female scale, measuring up to 6 mm, is tortoise shaped see Figure 14.11 and has a very thick cuticle. It may be a serious pest Figure 14.12 a Bud blaston rhododendron transmitted by a leafhopper b Capsid damage on apple. c Capsid damage on potato leaf Figure 14.12 a Bud blaston rhododendron transmitted by a leafhopper b Capsid damage on apple. c Capsid damage on potato leaf outdoors on vines, currants, top fruit and cotoneasters, sucking phloem sugars out of the plants. It is also found in...

Straw

Straw is an agricultural crop residue readily available in many parts of the country, but care should be taken to avoid straw with harmful herbicide residues. It is ploughed in or composted and then worked in. There appears to be no advantage in composting if allowance is made for the demand on nitrogen by soil bacteria. About 6 kg of nitrogen fertilizer needs to be added for each tonne of straw for composting to preventing soil robbing see p325 . Chopping the straw facilitates its...

Application of herbicides and pesticides

Spraying Knapsack

This subject is described in detail in machinery texts. However, certain basic principles related to the covering of the leaf and soil by sprays will be mentioned. The application of liquids and wettable powders by means of sprayers may be adjusted in terms of pressure and nozzle type to provide the required spray rate. Cone nozzles produce a turbulent spray pattern suitable for fungicide and insecticide use, while fan nozzles produce a flat spray pattern for herbicide application. In periods...

Three types of weed

Cleaversseeds

An ephemeral weed is a weed that has several life cycles in a growing season. An annual weed is a weed that completes its life cycle in a growing season. A perennial weed is a weed that lives through several growing seasons. Figure 13.4 Young cleavers. Seeds on older plants stick to the fur of animals Figure 13.4 Young cleavers. Seeds on older plants stick to the fur of animals The range of weed species includes algae, mosses, liverworts, ferns and flowering plants. These species display one or...

Carbon to nitrogen ratio CN

All nutrients play a part in all nutrient cycles simply because all organisms need the same range of nutrients to be active. Normally there are adequate quantities of nutrients, with the exception of carbon or nitrogen, which are needed in relatively large quantities. A shortage of nitrogenous material would lead to a hold-up in the nitrogen cycle, but would also slow down the carbon cycle, i.e. the decomposition of organic matter is slowed because the micro-organisms concerned suffer a...

Alternative growing media

In addition to open ground or greenhouse borders, plants may be grown in pots, troughs, bags and other containers where restricted rooting makes more critical demands on the growing medium for air, water and nutrients. Soil is an inappropriate material to use in containers as it tends to collapse when kept wet try watering a pot full of soil and note that it is not long before the container is only half full of soil. Soil is replaced in this situation by alternative growing media generally...

Growing medium analysis

The nutrient status of growing media varies greatly between the different materials and within the same materials as time passes. The nutrient levels change because they are being lost by plant uptake, leaching and fixation and gained by the weathering of clay, mineralization of organic matter, and the addition of lime and fertilizers. There are many visual symptoms which indicate a deficiency of one or more essential nutrients see minerals , but unfortunately by the time they appear the plant...

Chapter Plant reproduction

Plant Reproduction With Seeds

This chapter includes the following topics Figure 7.1 Euphorbia cyparissias 'Fens Ruby' Figure 7.1 Euphorbia cyparissias 'Fens Ruby' Figure 7.2 Range of flowers as organs of sexual reproduction having similar basic structure, but varying appearance having adapted for successful pollination or by plant breeding see chapter 10 a Iris chrysographes 'Kew Black' b Eryngium giganteum, 'Miss Willmott's ghost' c Trollius chinensis 'Golden Queen' d Rosa 'L.D.Braithwaite' e Hemerocallis 'Rajah' f...

Symptoms of disease and physiological disorders

Below in Table 15.2 is a summary of the most important symptoms to help the reader 'home-in' on disease problems and physiological disorders. Table 15.2 Some symptoms of diseases and physiological disorders Table 15.2 Some symptoms of diseases and physiological disorders 2. State the damage caused by three named fungal diseases. 3. Describe the life cycle of one named fungal disease. 4. Describe how the life cycle in the above fungal example is related to its control. 5. Describe the available...

Other aspects of weed biology

Particular soil conditions may favour certain weeds. Sheep's sorrel Rumex acetosella prefers acid conditions. Mosses are found in badly drained soils. Knapweed Centaurea scabiosa competes well in dry soils. Common sorrel Rumex acetosa survives well on phosphate-deficient land. Yorkshire fog grass Holcus lanatus invades poorly fertilized turf. Nettle and chickweed prefer highly fertile soils. The growth habit of a weed may influence its success. Chickweed and slender speedwell produce horizontal...

Photoperiodism

Photoperiodism is a term used to describe the plants various responses to day length, explained here in terms of flowering other responses include bud dormancy and leaf fall. Many plant species flower at about the same time each year, e.g. in the UK Magnolia stellata in April, Philadelphus delavayi in June and chrysanthemum in September. In many cases, flowering is in response to the changing day length, which is the most consistent changing environmental factor, in comparison with above-ground...

Plant form

Monocotyledon And Dicotyledon

Most plant species at first sight appear very similar since all four organs, the root, stem, leaf and flower, are present in approximately the same form and have the same major functions. The generalized plant form for a dicotyledonous and a monocotyledonous plant can be seen in Figure 5.2 . Internode with a leaf sheath enclosing the stem inside Tiller emerging from near ground level Figure 5.2 Generalized plantform a monocotyledon b dicotyledon Internode with a leaf sheath enclosing the stem...

Divisions of the plant kingdom

Division Hepatophyta

Figure 4.2 Four multicellular plant divisions horsetail with horticultural significance Figure 4.2 Four multicellular plant divisions horsetail with horticultural significance Mosses and liverworts. Over 25 000 plant species which do not have a vascular system see p92 are included in the divisions Bryophyta and Hepatophyta. They have distinctive vegetative and sexual reproductive structures, the latter producing spores that require damp conditions for survival. Many from both divisions are...

Fertilizer recommendations

The results of the growing medium analysis are interpreted with the appropriate nutrient requirement tables to determine the actual amount of fertilizer to apply. These tables usually have growing medium nutrient status indices to aid interpretation and results are normally given in kg of nutrient per hectare or grams of nutrient per square metre Table 21.4 . In some cases the amount of named fertilizer required is stated if another fertilizer is to be used to supply the nutrient the quantity...

Airfilled porosity AFP

The importance of supplying water to plants in a restricted root volume is usually understood, but the difficulties associated with achieving it whilst maintaining adequate air-filled porosity AFP are less well appreciated. Roots require oxygen to maintain growth and activity. As temperatures rise the plant requires more, but the amount of oxygen that is dissolved in water decreases. Even in cool conditions, the oxygen that can be extracted from the water provides only a fraction of the roots...

Budding and grafting

Grafted plants are commonly used in top-fruit, grapes, roses and amenity shrubs with novel shapes and colours. Rootstocks resistant to soil-borne pests and disease are sometimes used when the desired cultivars would succumb if grown on their own roots, e.g. grapevines, tomatoes and cucumbers grown in border soils. Grafting is not usually attempted in monocotyledons, since they do not produce continuous areas of secondary cambium tissue suitable for successful graft-unions. In top fruit,...

Stages in succession

Referring now to secondary succession, there is commonly observed a characteristic sequence of plant types as a succession proceeds. The first species to establish are aptly called the 'pioneer community'. In felled woodland, these may well be mosses, lichens, ferns and fungi. In contrast, a drained pond will probably have Sphagnum moss, reeds and rushes, which are adapted to the wetter habitat. The second succession stage will see plants such as grasses, foxgloves and willow herb taking over...

Nitrogen

Nitrogen is taken up by plants as the nitrate and, to a lesser extent, the ammonium ion. Nitrates and ammonium ions are utilized in the plant to form protein. Plants use large quantities of nitrogen it is associated with vegetative growth. Consequently large dressings of nitrogen are given to leafy crops, whereas fruit, flower or root crops require limited nitrogen balanced by other nutrients to prevent undesirable characteristics occurring. Although plants live in an atmosphere largely made up...

Woodlouse Armadillidium nasutum

The damage is confined mainly to stems and lower leaves of succulent glasshouse crops such as cucumbers, but occasionally young transplants may be nipped. A relative of marine crabs and lobsters, the woodlouse has adapted for terrestrial life, but still requires damp conditions to survive. In damp soils it may number over a million per hectare, and greatly helps the breakdown of plant debris, as do earthworms. In greenhouses, where plants are grown in hot, humid conditions, this species may...

The bullfinch Pyrrhulapyrrhula

This is a strikingly-coloured, 14 cm long bird, characterized by its sturdy appearance and broad bill. The male has a rose-red breast, blue-grey back and black headcap. The female has a less striking pink breast and yellowish-brown back. Damage. From April to September the bird progressively feeds on seeds of wild plants, e.g. chickweed, buttercup, dock, fat hen and blackberry. From September to April, the species forms small flocks that, in addition to feeding on buds and seeds of wild...

Vegetable production

The choice of cultivar is an important decision that has to be made before growing starts. There are many possibilities for each crop, but a major consideration is the need for uniformity. Where this is important, e.g. for 'once over harvesting' or uniform size, then F1 hybrids are normally used even though they are more expensive see p144 . Required harvesting dates affect not only sowing dates but the selection of appropriate early, mid-season or late cultivars. Other factors for choice...

Define the following terms family genus species subspecies ephemeral biennial perennial tender halfhardy hardy

Concise OxfordDictionary ofBotany. Oxford University Press. Baines, C. and Smart, J. 1991 . A Guide to Habitat Creation. Packard Publishing. Brown, L.V. 2008 . AppliedPrinciples ofHorticultural Science. 3rd edn. B utterworth-Heinemann. Dowdeswell, W.H. 1984 . Ecology, Principles andPractice. Heinemann Educational Books. Heywood, V.H. et al. 2007 . Flowering Plant Families ofthe World. Firefly Books. Hillier Gardener's Guide 2005 . PlantNames Explained. David and Charles....

Other effects on soil

Optimum For Most Mineral Soils

Beneficial soil organisms see p320 are affected by soil acidity and liming. A few soil-borne disease-causing organisms tend to occur more frequently on lime deficient soils see clubroot , whereas others are more prevalent in well-limed soils. Calcium sometimes improves soil structure and soil stability. It is probable that this is mainly because it encourages root activity and creates conditions favourable for decomposition of organic matter, yielding humus see p326 . Free lime in clay soils...

The classification of plants

Any classification system involves the grouping of organisms or objects using characteristics common to members within the group. A classification can be as simple as dividing things by colour or size. Fundamental to most systems and making the effort worthwhile is that the classification meets a purpose has a use. This is generally to make life simpler such as to find books in a library they can be classified in different, but helpful ways, e.g. by subject or date or particular use. Terms that...

Raspberry beetle Byturus tomentosus

The developing fruit of raspberry, loganberry and blackberry may be eaten away by the 8 mm long, golden-brown larvae of this pest. Only one life cycle per year occurs, the larva descending to the soil in July and August, pupating in a cell from which the golden-brown adult emerges to spend the winter in the soil. The adult female lays eggs in the host flower the following June. Spread is by means of the flighted adult. Control. Since the destructive larval stage may enter the host fruit and...

Deficiencies

Simple deficiencies are those in which too little of the nutrient is present in the growing medium. Most soils have adequate reserves of trace elements, so simple deficiencies in them are uncommon, especially if replenished with bulky organic matter. Sandy soils tend to have low reserves and so too have several organic soils from which trace elements have been leached. In horticulture simple deficiencies of trace elements are mainly associated with growing in soil-less composts which require...

Bacterial canker Pseudomonasmorsprunorum

Damage Caused Bacterial Canker

This disease affects the plant genus Prunus that includes ornamental species, plum, cherry, peach and apricot. Symptoms typically appear on the stem as a swollen area exuding a light brown gum see Figure 15.18 . The angle between branches is the most common site for the disease. Severe infections girdling the stems cause death of tissues above the infection, and the resulting brown foliage can resemble the damage caused by fireblight. In May and June, leaves may become Figure 15.18...

Sowing and aftercare in protected environments

Hydroponic Growing Pots

The ideal conditions for raising plants from seed can be achieved in a protected environment such as a glasshouse or cheaper alternatives such as polythene tunnels or cold frames see p16 . Most seeds grown in protected culture are sown into containers see Figure 12.2 Figure 12.2 Range of containers for growing plants a traditional clay pots b standard seed tray and half tray c standard plastic pots in range of sizes, compared with d 'long toms' and e half pots f biodegradable pots g compressed...

Removal of infected plant material

Whiteflies Apple Trees

With rapid-increase problems, such as peach-potato aphid and white rust of chrysanthemum fungus in greenhouses, removal of affected leaves is practicable in the early stages of the problem, but becomes progressively unmanageable after the pest or disease has increased and dispersed throughout the plants. Slow-increase problems, such as Fusarium wilt disease on tomatoes or carnations and vine weevil larvae found damaging roots of plants such as primulas and begonias, may be removed throughout...

Mineral uptake

Endodermis Zeamais

Minerals are absorbed to form the soil solution see Chapter 21 . The plants take up only water-soluble material so all supplies of nutrients including fertilizers and manures must be in the form of ions charged particles . The movement of the elements in the form of ions occurs in the direction of root cells containing a higher mineral concentration Figure 9.4 Cross-section of Zea mais root showing its structure in the absorption and transport of water and minerals Figure 9.4 Cross-section of...

Stem and bulb eelworm Ditylenchusdipsaci

The damage caused by this species varies with the crop attacked. Onions show a loose puffy appearance called bloat carrots have a dry mealy rot the stems of beans are swollen and distorted. Narcissus bulbs show brown rings when cut across and their leaves show raised yellow streaks. Life cycle. This species attacks many plants, e.g. narcissus, onions, beans and strawberries. Several strains are known, but their host ranges are not fully defined. The 1 mm long nematodes enter plant...

Centipedes

These animals resemble millipedes, but are much more active. They help control soil pests by searching for insects, mites and nematodes in the soil. This group of organisms, also called eelworms, is found in almost every part of the terrestrial environment, and range in size from the large animal parasites, e.g. Ascaris about 20 cm long in livestock, to the tiny soil-inhabiting species about 0.5 mm long . Non-parasitic species may be beneficial, feeding on plant remains and soil bacteria, and...

Mammal pests

A mammal, bird, insect, mite or nematode that is damaging to plants. A small selection of important mammal pests is included here. The rabbit Oryctolagus cuniculus The rabbit is common in most countries of central and southern Europe. It came to Britain around the eleventh century with the Normans, and became an established pest in the nineteenth century. Damage. The rabbit may consume 0.5 kg of plant food per day. Young turf and cereal crops are the worst affected, particularly winter...

Wireworm Agriotes lineatus

Chafer Grub

This beetle species is commonly found in grassland, but will attack most crops. Turf grass may be eaten away by the larvae wireworms resulting in dry areas of grass. The pest also bores through potatoes to produce characteristic narrow tunnels, while in onions, brassicas and strawberries the roots are eaten. In tomatoes, the larvae bore into the hollow stem. Life cycle. The 1 cm long adult click beetle is brown-black and has the unusual ability of flicking itself in the air when placed...

Potato blight Phytophthorainfestans

Potato Damaged Fungicide

This fungus is a member of the Zygomycota division of fungi see p74 . Damage. This important disease is a constant threat to potato production it caused the Irish potato famine in the nineteenth century. The first symptoms seen in the field are yellowing of the foliage, which quickly goes black and then produces a white bloom on the under surface of the leaf in damp weather. The stems may then go black, killing off the whole plant. The tubers may show dark surface spots that, internally, appear...

Other beetle pests

Viburnum Sawfly

Springtime attack of flea beetle Phyllotreta species on leaves of young cruciferous plants e.g. cabbages and stocks is a serious problem to amateur and professional horticulturist alike see Figure 14.21 . In recent years, four other increasingly common beetle problems have been reported. These are viburnum beetle on Viburnum opulus, V. tinus and V. lantana, rosemary leaf beetle Chrysolina americana on lavender, rosemary and thyme, red lily beetle Lilioceris lilii on lilies, and asparagus beetle...

Alternatives to peat

Perlite Alternatives

Whilst peat remains a popular choice as a compost ingredient, great efforts are being made to find alternatives in order to preserve the wetland habitats where peat is harvested. A list of some of the materials used is given in Table 22.1. Much progress has been made by using suitably processed bark or coconut fibre in composts. Along with several other organic sources they are waste-based and recycling them helps in conserving resources. All such alternatives must be free of toxics and...

Migratory plant nematodes

Tomato Roots Eelworm

The species of nematodes described above spend most of their life cycle inside plant tissues endoparasites . Some species, however, feed only from the outside of the root ectoparasites . The dagger nematodes e.g. Xiphinema diversicaudatum and needle nematodes e.g. Longidorus elongatus , which reach lengths of 0.4 and 1.0 cm respectively, attack the young roots of crops such as rose, raspberry and strawberry, and cause stunted growth. In addition, these species transmit the important viruses,...