During winter, deciduous trees go through a dormant period, but before their winter rest they shed their leaves in autumn and when the warm spring rains arrive their leaf buds swell and new young leaves unfold.
Many new leaves open with a reddish tinge as protection for the young leaves against sun scorch.
The leaves of the beech which open green are crumpled and protected by small hairs.
As the season passes and the days become warmer, the leaves lose the hairs and become smooth and flat. Any gardener who has worked around plane trees will testify how irritating to the throat these shedding hairs can be.
Have you ever noticed how the upper trunk, limbs and twigs disappear behind the leaves?
This is due largely to what is known as the mosaic pattern. All leaves need sunlight so they are arranged like a mosaic so that there is little, if any, overlapping to enable each leaf to get as much sun as possible.
The maples and sycamores are good examples of this with broad crowded patches where every leaf is exposed to the sunlight. They are so dense that scarcely a point of light penetrates. Consequently, few trees can grow underneath them.
So how is this leaf mosaic formed? One reason is the way leaf buds are arranged on the stem. As they are in spirals, or when in pairs alternating at right angles, the leaves avoid each other’s living space.
Each leaf also struggles toward the maximum sunlight in other ways such as lengthening and twisting leaf stalks or by adapting the angle of the leaf which may vary a little by day and by night.
Since green leaves find it difficult to live without sunlight, shaded leaves will die off and shaded buds may not develop. So a seemingly very dense screen of leaves is comparatively thin.
Another factor helping the leaves achieve their place in the sun is the general habit of trees elongating their lower branches so that their leaf-covered tips extend well beyond any danger of shading by the upper branches.
This demand of the leaves for sunlight also governs the shape of the leaves themselves.
They form a local leaf mosaic. Some leaves are indented, some long and narrow, some short and wide and others are composite, that is, made up of small leaflets arranged on a stem, and all grow on the tree so that each leaf and leaflet gets plenty of sun.
Mother Nature never ceases to amaze me.
The ginkgo is an ancient tree that still sets the standard in brilliant autumn colour when its green leaves, that are unique among seed plants being fan-shaped with veins radiating out into the leaf blade often splitting, turn a brilliant deep saffron yellow before falling.
This sole remaining species of tree, that was growing when the dinosaurs walked the earth, is a member of the conifer family, but unlike conifers, is deciduous. Long lived, some species are over 2500 years old.
This exceptionally decorative tree is very tolerant to pollution and has a high resistance to disease.
March 19: APSTAS North West meeting, St Paul’s Church Hall, 15 Thomas Street, East Devonport, 7pm. Jo Hopkins will speak on penguin conservation projects and volunteering opportunities.
March 19: The Australian Plant Society, Max Fry Hall, Gorge Road Trevallyn 7.30pm. Jon Hosford on ‘Aboriginal People’s Use Of Plants’. Visitors welcome.
March 20: Launceston Horticultural Society meeting, Windmill Hill Hall, High Street, Launceston, 8pm.
March 21: Launceston Orchid Society meets at Newnham Uniting Church, Launceston, 7pm.
Daily: Emu Valley Rhododendron Garden, Burnie, open 9am-5pm.