The propagation of trees and shrubs from seed is rewarding as it allows the gardener to practise a wide range of techniques that, if successful, produce something that has a long-lasting place in the garden or landscape. Although it is possible to purchase some tree and shrub seeds, these are limited to those kinds that can be successfully dried, so in most cases it is necessary for the gardener to collect his own seeds.
It is important to emphasize that the seeds used for propagation will only produce the kind of offspring that their heredity warrants. Seeds collected from species will probably come true; if collected from selected varieties then the seedlings will normally be of the species, unless of hybrid origin (see page 20). For this reason all fruit trees, which are highly specialized forms, should not be propagated by seed but must be increased vegetatively.
The chief problem associated with tree and shrub seeds is the presence of various kinds of dormancy, which in the extreme are sometimes combined and so present particular difficulties in getting the seeds to germinate.
Tree and shrub seeds are extraordinarily diverse in their shape and size- varying from the fine dust-like seeds of rhododendron to the large nut-like seeds of the horse chestnut or the oak, from the flat discs of wisteria to the hairy "parachutes" of clematis. All these considerations have a bearing on an individual plant's ability to survive and germinate: large seeds with a large embryo should have a much greater chance of successfully germinating than small seeds, as they have a larger food reserve, and therefore more small seeds than large seeds need to be collected.
Also affecting the quantity of seed to be collected will be the availability of seed from year to year. If this can be noted on a regular basis, it may give a guide for any storage requirements. Beech is an extreme example as it is reputed to produce good seed only once in "seven yearsr'; other plants also have definite periodic responses.
The gardener can either purchase his tree and shrub seeds from a reliable seedsman or he can visit gardens, parks and arboreta in the hope of coming upon some unusual tree
or shrub producing a crop of seeds. Gardeners are usually very generous with their plants and, if asked, will frequently be only too willing to give some seeds or cuttings.
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