Trees produce flowers which develop into fruits containing seeds, as their major means of reproduction. Certain tree species may also reproduce by root or trunk shoot cuttings, as well as by seed.
The terms “fruit” and “seed” are often used almost interchangeably by many people, even among those of us in the nursery trade. The easiest way to remember the difference is to recall that fruits (which includes cones, pods, etc.) contain the seeds. In some cases, such as the avocado, the fruit contains a single large seed; by contrast giant redwood trees have about 60 seeds in each cone.
An individual seed is an embryonic plant and typically contains food for post-germination, all enclosed in a protective seed coat. When ripe, seeds may fall to the ground and germinate beneath the mother tree, or be carried by gravity, wind, water or dispersed animals to germinate in other locations. Because animals feed on wild seeds, only a small number survive to germinate; therefore, it is advantageous for a tree to produce large quantities of seeds to assure their survival. Some trees seeds have poisons contained in their seed coats to discourage animal consumption. Trees seeds provide the bulk of the snack nuts we eat, such as walnuts, pecans, almonds, cashews, etc. Necklaces and bracelets are often fashioned from attractive tree seeds.
Trees in tropical and subtropical environments produce seeds which germinate quickly, without any period of dormancy. However, in middle and higher latitudes, tree seeds must overwinter and although ripe remain dormant until germination is triggered by local temperature and/or moisture conditions in spring.
Gardeners wishing to grow trees from seed need to know something about the plant they intend to propagate. If a tree is dioecious, bearing both male and female flowers on the same tree, the planted seed will result in a plant which resembles the parent species, because it has been self-pollinated. But if a tree is monoecious, with male and female flowers on different trees, with reproduction carried by out-crossing, the progeny from seed may not closely resemble either parent, but look like be a combination of the two.
The ability to store seed is important for subsistence farmers, who put aside seed from each year’s crop for use to plant in the following year, as well as for conservation scientists to keep endangered tree species in seed banks as a hedge against extinction in the wild. Seed specialists characterize all seeds, as either orthodox or unorthodox. Orthodox seeds can retain viability for long periods of storage in closed containers under dry or low temperature conditions; unorthodox seeds do not. The seed of many trees in tropical areas are unorthodox. If seed cannot be successfully stored in a seed bank, trees may be protected from extinction in the wild by being grown in special protected gardens of living plants, similar to a botanic garden.
At TreeWorld we have gained considerable practical experience in collecting and handling seeds and their germination and growth in the greenhouse and nursery. To add new species to the TreeWorld list, it is necessary to obtain seed from outside wild or cultivated sources. But once in our collection, when the trees mature, we can collect and utilize our own seed to maintain inventory.
If you have any question contact us.