Like all the flowering plants, trees reproduce and spread naturally by seeds. Some species and garden varieties also produce suckers or shoots directly from the roots, e.g. aspen and some of the elms. Seeds are the sexual means of propagation, formed by the fusion of pollen grains (male cells.) and ovules (egg or female cells).
In the case of trees without air sacs (larch,Douglas fir, walnut) the pollen grains can be carried only several tens of metres and the trees produce a large number of barren seeds. Trees pollinated by insects produce a far smaller quantity of pollen, as more of the grains manage to reach their intended destination on the body of the insect.
When the anther is ripe it bursts and releases the pollen grains, i.e. the actual male cells which are of microscopic dimensions. The pistil is formed of an ovary, containing the ovules, and a stigma, with either a sticky or a hairy surface, to trap the pollen grains. Quite often, the stigma is attached to the ovary by a stalk or style which may be very short, or long and slender.
Furthermore, adapted to pollination by wind-borne pollen, they frequently lack, or possess only rudimentary, petals, whose I light colours otherwise serve to attract insects. The mode of pollination largely determines the period of flowering of the various species.
Trees producing large seeds and thus requiring larger food reserves (oak, beech, walnut) may only bear them at two to four year intervals. Again, in harsher climates, e.g. in high mountain regions or in the north, where a longer time is required to accumulate the necessary food stores, the seed-bearing intervals may be longer.
Insect-pollinated trees such as the lime, black locust or cherry blossom later when the crown comes into leaf.
In the case of trees without air sacs (larch,Douglas fir, walnut) the pollen grains can be carried only several tens of metres and the trees produce a large number of barren seeds. Trees pollinated by insects produce a far smaller quantity of pollen, as more of the grains manage to reach their intended destination on the body of the insect.
When the anther is ripe it bursts and releases the pollen grains, i.e. the actual male cells which are of microscopic dimensions. The pistil is formed of an ovary, containing the ovules, and a stigma, with either a sticky or a hairy surface, to trap the pollen grains. Quite often, the stigma is attached to the ovary by a stalk or style which may be very short, or long and slender.
Furthermore, adapted to pollination by wind-borne pollen, they frequently lack, or possess only rudimentary, petals, whose I light colours otherwise serve to attract insects. The mode of pollination largely determines the period of flowering of the various species.
Trees producing large seeds and thus requiring larger food reserves (oak, beech, walnut) may only bear them at two to four year intervals. Again, in harsher climates, e.g. in high mountain regions or in the north, where a longer time is required to accumulate the necessary food stores, the seed-bearing intervals may be longer.
Insect-pollinated trees such as the lime, black locust or cherry blossom later when the crown comes into leaf.
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Wood garden planning is an ideal material for blending a house garden into a natural setting, especially one surrounded by tree.
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