The trees and shrubs treated on this page are grown more for interest than for the fruit, if any, that they may produce.
Their methods of propagation are similar, except that of avocado. Fill a pot with seed compost and with the finger-tips firm gently to the corners and the base of the pot. With a presser board strike off the compost level with the rim, then press the compost to ¿-f in below the rim. Sow the seeds and push them into the compost with a presser board. Cover the seed with its own depth of sieved compost. Water the pot thoroughly, label, cover with glass and a piece of paper, and place in a warm (21°C/70°F) environment.
As soon as the seedlings appear remove the paper and glass and stand the pot in good light, still in the warm. To prevent disease, spray regularly with Captan or a copper fungicide.
Prick out the seedlings once they are large enough to be handled. Knock the sides of the pot to loosen the compost. Separate the seedlings with a dibber so root disturbance is reduced to a minimum. Fill some pots with John Innes No. 1 compost or similar (see page 12). Make a hole with a dibber and plant the seedlings into individual pots; firm in, water and label. Keep the seedlings at a warm (21°C/70°F) temperature until re-established.
The propagation of citrus trees and shrubs from seed is relatively simple, although it must be remembered that the resultant offspring will be of only the general type of fruit. It is necessary to propagate vegetatively if the particular variety is required.
In temperate climates most citrus fruits grow on medium-sized trees. They will not mature to that size and produce fruit in a cooler climate, where it is, however, quite possible to grow bushes that will produce fruit of a sort, provided they are kept warm in winter. The main problem is that citrus plants are evergreen and therefore need to be kept growing all the year round.
The following citrus are species and will come true: lime (Citrus aurantiifolia); Seville orange (C. aurantium); lemon (C. limon); grapefruit (C. x paradisi); and sweet orange (C. sinensis).
Extract the pips from the fruits. Although they will withstand a limited degree of drying, it is better to sow them fresh.
Space about five seeds round a pot filled with compost. Generally, citrus seeds will germinate best at a temperature of 21°C/ 70°F and, if kept damp and warm, will appear in three to four weeks.
Coffee trees can readily be propagated from seed but, like all fruit trees, the most desirable clones have to be propagated vegetatively. Seedling coffee trees do not produce reliable crops, but nevertheless most trees grown from seed do produce some fruit even when quite small: a 2-3ft tree grown in an 8-9in
pot will flower and fruit, given suitable conditions.
A good coffee tree to grow from seed is Coffea arabica, which produces bright red berries that mature to a deep crimson, and contain one or two white bean-like seeds.
The seeds germinate readily if sown fresh and without drying; dried seed can be reconstituted to some extent by soaking.
Station sow about five seeds to a 3j in pot; cover with compost and water in a fungicide such as Captan or Benlate. Keep at a reasonably high temperature (18o-21°C/65o-70°F).
The seedlings are particularly prone to damping off, so spray regularly with Captan or zineb once the seeds have germinated. This should be in about four to five weeks.
Always keep coffee trees in a warm (21°C/70°F) place and feed them occasionally.
Most stones that can be extracted from imported boxes of dates are viable and so can be used to propagate new plants. Date palms do not fruit until they reach 15-20 ft.
Sow seeds individually in pots. Although date palms will germinate at relatively cool temperatures, they will respond more effectively and rapidly at temperatures of at least 15°-21oC/60o-70°F, when seedlings should emerge within seven to eight weeks.
Date palm seedlings are prone to damping off, so spray regularly with a fungicide.
In common with other fruiting trees, the most reliable avocado clones require vegetative propagation. Avocado trees reach 15-20 ft before they mature and produce fruit, but they are unlikely to fruit in a cool climate.
Avocado stones are large and are germinated individually in pots filled with seed compost. In a warm, humid environment (21°C/70°F) lay the stone across the top of the compost to discover which is the right and which is the wrong way up. When, in about three to four weeks, the seedling's stem and roots appear, set in the right position in the soil and return to a warm, humid atmosphere.
Avocado stones left to germinate in water are difficult to transplant satisfactorily into soil so avoid this method of propagation.
The propagation of plants from roots is a simple ana rapid process that has on the whole been neglected.
As long ago as 1662, John Evelyn wrote in his famous book Silva of the possibility, when a tree was dug up, of leaving some of its roots in situ to develop as new trees. By 1731 Philip Miller, in The Gardener's Dictionary, was describing the propagation of certain trees from root cuttings as an established practice amongst gardeners.
Since then, although it has been demonstrated that it is possible to propagate in this way, the technique has never become standard, except in the case of a small number of mainly herbaceous plants. It appears to have been ignored largely because of the aura of uncertainty associated with the success of this technique. Such a technique, however, should be popular because large quantities of plants can be produced from a very small amount of propagating material. Therefore, it is necessary to sort out the relevant features involved in this kind of regeneration and determine a system that eliminates the greater proportion of the uncertainty.
Initially, it is important to divide plants into two categories: those that will propagate from roots; and those (apparently) that will not. A plant that can produce adventitious shoot buds on its roots should be suitable for propagation from root cuttings, although ultimately this is not necessarily an indication of its ability to regenerate a completely new plant.
When the various plants capable of producing adventitious buds on their roots are categorized, it will be seen that the responses vary: some plants produce buds on their roots as a natural growth process, whereas others require some other agency to stimulate bud initiation. Some of them have buds that elongate and develop as shoots; others do not grow in this way.
There are three relevant methods of propagating from roots: natural suckering and division; suckers from undisturbed, but isolated, roots; and root cuttings.
When a plant is lifted, inevitably some roots are severed and remain undisturbed in the soil. During the subsequent late winter and spring, these roots will, if the plant is capable, develop suckers. These suckers, if left to establish, can then be lifted and replanted at the end of the growing season. Plants that are sometimes propagated this way include Rhus (the sumachs), Robinia,
Ailanthus, Rubus and Chaenomeles. However, most plants that regenerate in this way are also fairly easily propagated from root cuttings and, as the latter method makes better use of space, the former technique is not widely employed.
Natural suckering occurs in some plants such as lilacs and cherries. The plants send up isolated shoots that develop their own root system.
Towards the end of the growing season, sever the roots of a sucker from the parent plant and leave it to establish. After a few weeks, lift the sucker and transplant.
If a grafted plant such as a rose sends up a sucker, it should be completely removed immediately. If this is not done, the grafted plant will be weakened as the sucker is from the rootstock and not from the cultivated variety.
1 Dig deeply round a suitable plant in autumn. Ensure all the roots are cut right through.
2 Lift just the plant, leaving the roots undisturbed in the ground to establish as new plants.
3 Transplant these suckers at the end of the growing season.
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