You should now have your plant in the right light and the- right temperature: the next urgent need as far as the plant is concerned may well be a drink. All plants consist largely of water, perhaps as much as 90°0, which is being lost steadily bv day and night in the form of water vapour from most of the above-ground parts of the plant. It is replaced mainly via the roots, into which water penetrates from the soil or compost. If the growing medium is drv, obviously the plant will become dry. It will wilt and eventually die if the lack of water is sufficiently prolonged.
Exactly the same effect is produced, with the addition of yellowing of the lower leaves, if the compost is made too wet. But this time the roots suffocate—completely waterlogged thev cannot get at air which contains the oxygen thev must have to live. The roots stop working and die, and so no water is passed up to the leaves and stems.
There is another reason why plants must have water. The minerals plants use as food, such as phosphorus, potassium and magnesium, ate dissolved in the soil water and so are absorbed by the roots, along with the water. If a plant has the wrong amounts of water it gets the wrong amounts of nutrients and therefore becomes unhealthy.
The technique for watering is simple. Each time you water, give sufficient to till the space between the surface of the compost and the rim of the pot, pouring it on steadily until full. Allow the pot to dram off surplus water; if there is none, give another watering and repeat the process. Generally only one dose is needed, if you are watering at the right times, because the compost beneath the dry surface will still be a little damp.
What you should never do is to give the plant little dribbles of water. All that happens is that the compost surface becomes moistened while the rest of the soil gradually dries completely. Eventually the soil shrinks right away from the sides of the container, and then when you water much of it is wasted as it trickles down the space thus made and out of the drainage holes. Always give a good watering; provided the compost is correctly made up the unwanted water will drain away.
The decision on whether to water or not is more difficult. The obvious sign of water-need is a wilting plant, but it should not be allowed to get to this stage. Long before wilting occurs, compost containing soil will begin to dry on the surface. The surface compost will feel dry to the touch and will be a lighter brown than that beneath. The pot will be less heavy than it was, and if it is a clay one will make a ringing noise when tapped with a piece of wood instead of letting out a sound like a dull thump.
Peat composts, without soil, are slightly different. They tend to stay adequately moist for longer, and then suddenly, within □ day or two, they become almost completely dry. If you suspect water is beginning to run short, you have to watch very carefully so that you water just before this happens. This problem of sudden drying is particularly noticeable if the plants are in plastic containers. Peat composts get very light when drv, so the weight of the pot and plant is a good guide; the compost will also change colour a little on the surface, though not so obviously as with the soil composts.
By watering according to these methods, you will be giving the plant what it needs at the right time. The intervals between waterings will never be regular, and one of the worst things you can do is to water every Saturday morning at to o'clock, or in the afternoons on alternate Thursdays. The need for water will vary, depending on the temperature, the humidity, the rate at which the plant is growing, the size of pot and plant, the type of plant and the type of compost.
If your plant has got really dry, put the whole pot in a bucket of water so that the compost surface is covered, and leave it there until bubbles of air stop coming up from the surface. This is the only way to make sure that the centre of the root-ball has been thoroughly wetted.
In summer, plants will need to be watered more often, because they transpire more water at higher temperatures. In winter, sufficient water should be given to keep the soil-ball moist. Depending on the temperature, this may mean watering only once a fortnight, whereas in summer liquid refreshment may be required every two or three days.
Use water at room temperature, preferably rain-water, or water which has been boiled or softened, so that it is slightly acid. No plant minds acidity, but some plants don't like alkaline or chalky (hard) water, so it is better to be on the safe side and use lime-free water whenever possible.
1 have mentioned humidity once or twice and you may be wondering why it is so important and how to get it right.
As 1 said in the previous section, plants, even desert plants, consist largely of water. The water circulates through the plant carrying mineral foods and other substances and helping the plant to maintain its structured rigidity. What causes the water to move through the plant is that the ¡eaves constantly let water out in the form of vapour (this process is called transpiration). When water goes from the leaves it creates a kind of vacuum which has to be filled by water from lower down the plant. In this way the leaves constantly 'pull' water up the plant. If the atmosphere is dry, the roots cannot absorb water as quickly as the leaves lose it. So the leaves become dry, may wilt and turn brown at the edges. If the air is humid—that is, already full of water vapour -it won't take much more from the plant which therefore transpires slowly so that the water inside moves slowly and the cells remain turgid and the leaves stay healthy. The drier the air the faster water moves and the more likely is it the ¡eaves will suffer.
Remember, every plant is adapted to live in a particular environment. If a plant (e.g. a cactus) grows naturally in a dry atmosphere then it adapts by having fewer outlets for water vapour. To get your indoor plants to grow successfully you have to provide them with the humidity conditions that they like best.
If you put several plants in a group, they will make their own local humidity, and you will find they flourish in such conditions.
Specimen plants, grown alone, can be misted or sprayed with clear water every day, or more often if necessarv. Shallow containers of water put close to them will provide a large surface from which water can evaporate. Dishes of water, with shingle in the centre for the pot to stand on, will serve the same purpose, A larger container, surrounding the one which the plant is in, can be packed with moist material to fill the space between the two. Peat, scrunched-up newspaper, oasis or polystyrene granules will do—in fact anything which absorbs water.
Whatever you do, the plants must not be stood on a shelf over a radiator. The roots get lovely and warm, but the compost dries up visibly, and the atmosphere is so dry that the plant is likely to shrivel up before your eyes. It is, actually, one of the quickest ways of killing a plant.
Any living organism which uses energy needs fuel, in the form of food, to replace the energy expended in growing, working and/or playing. Plants need energy for growing, which they do all the time, and the fuel, or food, for them is partly absorbed from the soil, or com post, by the roots and partly made by the leaves during photosynthesis. Beyond supplying exactly the right amount of tight and warmth, there is not a great deal mote that can be done as far as the leaves are concerned, but you can heip the roots considerably by supplying the necessary elements.
The ones considered to be most important are nitrogen (N), phosphorus (P) and potassium (K). Broadly speaking, nitrogen is essential for healthy growth of leaves and shoots—all the vegetative parts. However, plants have no way of absorbing pure nitrogen gas, which is in the air around them; they have to get their nitrogen from compounds containing the element mainly from nitrates. Phosphorus is used throughout the plant, but is especially needed by the young roots and root tips. Potassium is associated with the plant's maturity, and is used to produce flowers, viable seeds Grooming and pruning and fruits, and to ripen the plant's vegetative buds so that they flower the following season.
Many more elements are used bv the plant, for instance magnesium, which is used to make chlorophyll, calcium used in cell walls, iron, sulphur, boron, molybdenum, copper and so on. However, these are 'trace' elements, meaning that the plant only needs them in minute quantities, or traces. It can be safely assumed that the necessary quantities will always be contained in a good compost.
The elements you will probably have to help the plant with arc N, P and K, because they are used quickly and in appreciable quantities. In particular, nitrates have to be given because they are very soluble and are easily washed through the compost by watering. There are many proprietary brands of mixtures of these nutrients in liquid form (liquid fertilizers), each with different quantities of N, P and K. They are, in fact, tailored to the particular needs of various plants. For example, one which contains a relatively high percentage of K and little \ should be chosen tor flowering plants. Similarly, one with plenty of N is the best for plants grown for their foliage.
The proportions of nutrients in a fertilizer will be shown on its container as percentages, thus N 6%, P,Os k,0 8% (those particular proportions would be useful for flowering plants). Instructions for rates of dilution and frequency of application will also be given bur as you get to know your plants' needs, you can adapt the instructions slightly to fit each plant.
Fur most plants you should start liquid feeding about halfway through the summer, if the plant was freshly potted in spring, and cease in autumn, Once every two weeks is an average application frequency. Compost must always be damp when the solution is given, and feeding can take the place of the ordinary watering which would otherwise be done.
As with humans, the needs of individual plants vary: some are greedy and will use all the food in the compost long before mid summer, others, especially bulbs, may-need feeding at quite different times, as they have different life cycles. Some, such as bromeliads and cacti, hardly need any food; others, like the Christmas cherry, need not be fed until their fruits have set and begun to swell. Plants in soil-less composts will need feeding almost from the time of potting.
Plants change their appearance when they are short of nutrients. Usually the leaf colouring alters. The symptoms van- according to the deficiency and can be verv marked; they are described in detail on page 28,
As your plants grow, their shapes will change. Leaves will mature until they arc no longer useful, flowers will fade, and shoots, especially those of the climbers, may become too long and spoil the outline of the plant. This is when grooming makes the difference between an ordinary plani and a first-class one.
Old yellowing, damaged or brown leaves should all be taken off rhey are no longer any use to the plant. Broken or injured stems should he cut off cleanly below the damaged part, just above the ¡unction of a leaf or another shoot with the stem. Dead flowers need removing, especially if they have fallen onto a leaf below. Plants with large leaves look better for, and relish, being wiped gently with a soft moist cloth, to clean off dust and grit and the white spots left after spraying with hard water. Dust and grit on the leaf block the stomata, and cut down the amount of light reaching the leaf. As well as being ugly, dust can be chemically damaging if you live in an urban area. However, hairy leaves will be damaged by wiping and prickly cacti cannot be sponged; such plants should be gently brushed.
If you want a foliage plant with glossy, mirror-like leaves, there are proprietary plant polishes available w:hich will supply this effect without harm. However, many plants in good health will be naturally shiny and this extra gloss can make a plant look rarher like an artificial one.
Keep trailing plants shapely k - 1 Y -
stems Climbing plants may v1 * v occasionally need cutting ju £
Besides removing damaged material, some plants need regular pruning every- year to flower well and maintain their bushiness. In general this is done in very late winter, just before repotting, and usually consists of cutting the previous year's nea> growth back by half. This spurs the plant on to produce plenty of new shoots, on which there will be flowers.
Climbing plants may need cutting down almost to the base, or by about half, in spring, or may even need cutting back during summer to keep them within the space available, or to thin them. The shoots to remove are the smallest and weakest ones, those that are not flowering well, and finally, any that are still causing crowding.
One form of pruning is known as 'pinching back'. This is carried out in late spring and the technique is to mp out the tip of a shoot, just above a leaf or pair of leaves, sometimes back to the second or even third pair. More shoots grow in the axils of leaves lowrer down the stem, and the result is a bushier plant, or one writh more flowers.
Trailing plants can become straggly, with yards of bare stem and a few leaves at the tip; pruning them back will induce 'breaks' higher up the main stem.
Always supply supports for climbing plants and for tall, delicate plants. Put the supports in position in good time before the plants become misshapen. Tie the stems loosely to the supports so that the stems are not strangled.
At some stage in the not-too-distant future your plants will need more room for their roots and also fresh compost. Nowadays most plants are sold in plastic pots, though clay pots can still be bought. The plastic ones are made in various colours besides terracotta, such as green, black or mottled; they are light to carry and more or less unbreakable, though the smaller ones tend to crack easily around the rim. Clay pots are heavier and cost more, but last indefinite!v, provided vou do not drop them, and many people still prefer them.
Troughs and window-boxes can be made of wood, of expanded polystyrene which feels, and is, warmer than the surrounding temperature, of mixed stone and concrete, or of fibreglass moulded and coloured to look like the old Italian lead containers. Wooden tubs, parslcv pots, strawberry barrels, tower pots and urns provide variation of container shapes and sizes.
Whether vour plant is strong and healthy or whether it languishes and eventually fades away depends on the compost you put it in. You will have seen from the watering section that the roots must have oxygen and, from the advice on feeding, that various minerals are essential, so it is no good filling the pot with earth dug out of the nearest flower-bed in the garden, if you are lucky enough to have one, because it will not have the right structure or food balance for a pot plant.
The roots of container plants live in a highly artificial world, and the plant relies on you to give it what it needs just as a domesticated animal does, but a plant's reliance is even greater because it cannot attract your attention.
A good standard compost contains sieved loam, coarse river sand, granulated peat, fertilizer and chalk. These ingredients are used in proportions which have been experimentally determined as the best for the majority of container-grown plants. Variations can be bought or made to suit groups of plants which have special needs, but in general a standard compost will ensure good drainage of water, aeration of the compost, a supply of food for three months or more, and a quantity of water in the compost sufficient for the roots, without drowning them. Being fairly heavy, such a compost also enables the roots to anchor the plant firmly in its pot.
Good loam or soil-containing compost, however, is becoming scarce, expensive and costly to transport. A modern substitute is soil-less compost, which consists of peat and sand, usually in the proportion of j 11, with some fertilizer added. Soil-less compost is proving to be quite satisfactory, and even better for some plants than the previously used loam compost. It is light to carry, but a plant with a lot of top growth which is grown in soil-less compost in a plastic pot may become top-heavy and fall over, so such composts need to be used with caution. Large plants are still best grown in soil-based composts. Either type can be obtained in various pack sizes at chain stores, garden shops and garden centres, or you can make up your own mixtures as you become more experienced.
The time for repotting plants is when the roots have just filled the pot, although the time of year should also be taken into account. Vou can repot during the growing season, up to about the beginning of late summer, but the best time is usually early spring.
In autumn the plant gradually ceases to produce new
The technique of repotting. (1) to (5) Wtien repotting a prickly cactus use a cardboard holder to avoid scratching the hand or damage to the plant
The technique of repotting. (1) to (5) Wtien repotting a prickly cactus use a cardboard holder to avoid scratching the hand or damage to the plant growth, and in winter will be resting so that the roots do not take very much water and food out of the compost. It" you put the plant into a larger pot (called pot-ting-on), with new compost, in eariv autumn then the roots would not absorb either the extra water present in the larger pot or the fertilizer. The compost would become 'sour' because the unused, stagnant water encourages the increase of bacteria which produce substances harmful to plant roots.
When you are potting-on into a larger pot—use one which allows 1.5-2.5 cm (i 1 in) (depending on pot size) all round between the side of the root-ball and the inside of (he pot. If the pot is clay, put a few pieces of broken clay pot at the bottom to help with drainage and aeration, and put a little compost on top.
Turn the plant out of its old pot, gently loosen the soil-ball a litilc with your fingers, and cut off" any straggling roots or any which are brown all the way through. White roots are young, though remember that a plant which is only just coming out of its winter rest will not have any.
Put the plant centrally in the new pot, and make sure that the level of the surface of the soil is 1.5-4 em (Jin) from the top of the pot to allow enough space for watering. Fill the sides in with compost, firming it with your fingers only—-your thumbs will put too much pres sure on the compost and compact it—tap the pot base on the working surface to level the compost, and water at once. Then put the plant somewhere warm and slightly shaded.
Soil-less composts should be filled in and lightly firmed only.
If you are repotting without changing the size of the pot, because the plant has reached its full size but has used all the goodness in the old compost, tease our what remains of the old compost, spread the roots out as naturally as possible, and crumble the new compost in over them until the pot is full, firming as you go.
Prickly cacti can be difficult to deal with but vou can use a pair of tongs or a paper collar round the base of the plant, or a very tough pair of leather gloves.
Plants which grow fast may need potting-on once or twice more during the growing season, but generally the spring repotting is sufficient, and some only need this every two years. Once more, be guided by what the plant needs rather than 'because it is spring it must be repotted'. A very frequent need for water, a rather pale plant, roots wound round the soil-ball or coming out of the drainage holes, are ail signs of an urgent need for a larger pot and/or fresh compost.
One final point: break up the compost surface occasionally with a household fork, to prevent the forma tion of a crust that will encourage the growth of moss and prevent fresh air percolating into the growing medium.
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