Embryos of New Life
Without doubt there are more plants raised for our gardens from seed than by any other method. Annuals and vegetables are almost exclusively propagated in this way.
There are tliree main advantages in raising plants from seed. Firstly, seed is a relatively cheap way of obtaining large numbers of plants.
Secondly, good seed has less chance of carrying disease than vegetatively-produced plants, and thirdly, plants raised in the environment in which they will mature will be stronger and more tolerant than imported plants.
A seed is a very efficient reproductive structure produced by flowering plants and conifers. It has a protective coat and contains an embryo of a new plant and very often a food that nourishes the embryo after germination.
The endosperm or food storage area of seeds also nourishes the seedlings.
The embryo is formed after pollination of the female gamete, or egg, in (he ovule by the gamete from the pollen grain.
When the fertilised ovule develops, it is usually encased in a fruit or pod, though seeds of conifers are naked. After fertilisation, the seed itself remains more or less dormant until conditions of moisture and warmth promote germination.
When a dry seed is given water, its colloids take up the moisture and soften the seed coat, often in a matter of hours, although sometimes it may take quite a few days.
I hc enzymes in the protein system become active, and increase the metabolism rate in the cells. New energy becomes available for further development.
Water uptake and respiration continue while new materials for growth are being synthesised as the enzymes reduce the fats, proteins and carbohydrates stored in the seed to simpler compounds.
Stock seed is the term used by companies that provide foundation seed to contracted growers who in turn produce more seed for the companies.
The seed companies maintain strict standards and supervise the fields of the individual contractors during the season.
Many high-grade seeds are hybrid cultivars, produced by the repeated crossing of two or more lines of parentage. This is accomplished by using inbred lines of seeds or by asexual propagation.
Seed and seedlings
The qualities, characteristics and forms of the seeds produced by plants vary greatly according to species or variety and environment.
Some seeds arc ready to germinate right after they are produced and others need a period of dormancy or a period of cold before they will grow. Some grow quickly and some take a long time to reach maturity.
The way you harvest seed important
The way you harvest, ripen and store seeds depends upon germination requirements and the factors that influence the dormancy of each type of seed.
The qualities, characteristics and forms of seeds produced by plants vary greatly according to species, variety and environment.
Some seeds are ready to germinate right after they are produced, while others need a riod of dormancy or a period of cold before they will grow.
Germinating pawpaw seed
For example, some seeds, including many tree seeds, must never be allowed to dry out before planting. For shipping, these seeds should be collected as soon as they are ripe and carefully packed so they cannot dry out.
Most other seeds need to be stored in a dry, dark place but may require scarring or a special cold treatment before they will break dormancy and germinate.
There are several reasons why a seed remains dormant. Some, such as those of walnut, olive, peach, and plum, plus many flowers and shrnbs, have very hard coats which must be injured before they begin to absorb water and germinate.
In nature, natural weathering will scarify the seeds, but the gardener or grower must do it himself by tapping them with a liammer, filing them or rubbing them with sandpaper.
Certain tropical and desert seeds have an inhibitor in the seed coat and must rest until weather conditions develop which can break down the inhibitor.
Seeds of some palms and orchids have embryos so tiny that they must have a quiescent period before they are able to germinate. Other seeds have a rather short period of so-called internal dormancy while they are dry ing out after being freshly harvested.
The dry storage breaks this dormancy, which is a shallow one compared to the deep dormancy of winter-dormant seeds.
Deep dormancy requires long periods of moisture and chilling. Kept in the refrigerator, these seeds are planted during the summer, kept moist, and allowed their cold dormancy during the following winter.
To stratify seeds in the refrigerator, mix the seeds with slightly moistened sand, peat moss or sphagnum moss, or a mixture of sand and moss or sand and vermiculite. Store them in polyethylene bags.
After a spell in the refrigerator at around five degrees C, watch for the beginnings of germination and when you see the seeds are starting to grow, bring them out and sprinkle them on flats, adding a little water daily so they will stay moist.
Three months is the usual storage time needed for fruits like cherries, currants and gooseberries.
Stages of seed germination
Too much or too little water at the time of germination affects seeds. Celery, for example, needs a great deal of water, but spinach does not.
Other seeds that don't need much water, although it won't harm them, include cabbage, turnip, sweet corn, cucumber, onion, carrot, tomato and many herbs. Those needing quite a bit more are beans, peas, beetroot, and lettuce.
Of course other conditions and the natural longevity of seeds also contribute to the success of germination.
Onions are only considered to be viable for a year, along with leeks, parsnips and corn; ¡whereas pea, bean, cabbage, and cauliflower seeds will last for three years, and melons up to seven years.
Be sure to inspect seeds received or saved to make sure they are clean, all of one kind, uniform in si/c, and plump and fresh looking.
If in doubt, put the seeds through a germination test by scattering a specific number of seeds between two damp towels.
Place them in a warm, dark place and, after the required germination period, count how many have sprouted. If it is less than 50 percent, consider using other seed.
Hardy and quick-growing annual flowers and vegetables are usually started in beds in the garden.
More tender plants, slow-growing plants, those which take a long time to germinate, and those with seed so fine that weeks are required to develop the seedlings into manageable plants, arc usually planted indoors.
Sowing seed in small containers
Perennial flowers may be started indoors in midwinter in the colder areas of Australia and may be expected to bloom the first year from seed.
They may also be sown in spring, in a special outdoor nursery bed and then transplanted in autumn to their permanent garden positions.
Bieimials may be planted out anytime from spring to autumn. For early vegetables, seed may be sown indoors and the plants hardened in a sheltered place outside before they are set in the garden.
Vegetables such as cucumbers and squash, normally planted directly in the garden, may also be sown inside in pots or paper containers.
At the normal time for planting in the garden, if all danger of frost lias passed, these early plants may be set out without disturbing their roots.
Seeds planted outside are usually planted in the soil in which they will grow during the entire season. The soil must be properly prepared in advance, by adding manure and compost or whatever that particular vegetable or flower needs. t
If the seed is to be planted in rows, a drill or trench may be made by using the edge of a board to keep the row straight.
Depth of planting depends upon the size of the seed, the consistency of the soil and the season of the year.
The usual rule is to plant a seed at a depth that is three or lour times the size of its diameter.
This rule is modified by soil. Heavy clay soils hold more moisture so seeds need not be planted as deeply.
Sandy soil will dry out faster at the top, so the seed may need to be planted deeper. Seed should never be overwatered during germination, nor should it be kept too cold. If the soil is heavy and wet, it will be cold beneath the surface early in spring.
Seed will germinate more rapidly if it is sown on the surface. When the soil is warmer, seed can be planted further down.
Since seeds need air as well as water during germination, the soil should be granular so that air may penetrate to the depth of the seeds so they can breathe.
Fine seed should be sprinkled on top of the soil and firmed with a board, the back of a hoe or with the hand. A very slight sifting of sand or fine compost over the seed will help keep it moist.
Sand will also help to control damping-off and will rebuff slugs and snails, which love young seedlings.
Damping-off describes the wilting and early death of young seedlings. It is caused by parasitic fungi living in or near the surface of the soil.
Crowding of seedlings, high humidity and lack of sufficient aeration all favour damping-off. Remedial measures include ensuring proper ventilation, drying the soil in which the seedlings are growing and sprinkling powdered charcoal on the surface of the soil.
Summer-planted seed always needs to be finned. Spring planted seed may or may not need it, depending on soil and weather. Summer-planted seed should be covered with a sheet of paper or fine, dried grass clippings to protect it from dry ing out until germination.
If seeds are planted in a pot, the bottom quarter of the pot should be filled with broken pieces of pottery or gravel to provide drainage.
Label each pot with the name of the seeds planted
If using a seed raising tray cover the bottom of the tray with sphagnum moss. Cover with moist soil and sow the seed thinly.
If more one kind of seed is planted in a container, the seeds should be chosen to germinate at about the same time so that all will be ready for transplanting together.
After the seeds have been placed in rows, sand or fine compost should be spread over them to the correct depth, which is never more than three or four times the diameter of the seed.
Finn the soil and water it, either from above with a very fine spray or from below, by plunging the container into water almost as deep as the soil. When wet patches begin to appear on top of the soil remove the container from the water and drain.
Each pot or container should then be carefully labelled with the name of the seeds planted.
Seed trays may be covered with two or three sheets of newspaper to preserve surface moisture until germination starts, but the cover should be removed occasionally for ventilation or if fungus appears.
The temperature for seed genni nation may usually be somewhat higher that what the plants will stand after growth has started. Soil should be kept moist, but not wet during this period.
As soon as the first green begins to appear the covering should be removed.
Gradually, as the seedlings sprout and the roots stretch down into the pot, watering may be lighter and less frequent, but the container should never be pemiitted to become dry.
If seedlings are too thick they will need to be thinned. Occasionally when fine seed is planted, it will come up unevenly, with thick patches in places in the container.
These patches should be thinned with tweezers or excess seedlings cut off with nail scissors so as not to injure the roots. Crowding at this stage will almost inevitably result in damping-off.
When seedlings are 2 to 3 cm tall, they should be transplanted to about 4 cm apart.
The usual rule is to transplant when the first pair of true leaves has fonned. By this time seedlings will have developed roots that are in proportion to top growth.
Soil in the new tray may have a small amount of compost mixed with the loam and sand, but the mixture should not be too rich.
If the roots must seek further for food, they will build a strong, healthy root system, which is very important to the plants at this point in their growth.
Some plants benefit from a second transplanting which develops even stronger root systems.
About two weeks before the seedlings are to be planted in the garden, they should begin their hardening-off.
At first they should be set outside during the warmest part of the day. Gradually the period when they are left outside may be lengthened into the cooler parts of the day.
Transplanting should be done on a cloudy day, early in the morning or in the evening when the sun will not shine directly on exposed roots.
If possible, for several days after transplanting, plants should be protected from the direct rays of the sun by newspapers folded in a 'cap' shape or a piece of shadecloth.
Water with a weak solution of liquid seaweed/fish emulsion to protect them from transplant shock.
Transplanting seedlings into 8 cm pots
These plump, smooth, variously coloured worms attack a number of garden plants. Young larvae feed on the lower surfaces of leaves, and the older larvae chew through plants stems near ground level.
'cutworm'. Cutworms burrow down several centimetres into the soil to pupate, and grow to be night-flying moths. When disturbed, they typically coil themselves up.
To protect young plants, cutwor collars are easy to make. Use a piece of cardboard or stiff paper about 8 to 12 cm in length and wrap it loosely around the stem of each seedling, sinking it about 3 cm into the soil.S
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