![]() So what causes the beautiful displays of autumnal colour? The green colour of spring and summer leaves is the result of chlorophyll, the chemical that enables the plant to photosynthesise and produce the energy it needs to grow. Some trees that lose their leaves in cold conditions at higher latitudes keep their leaves-and their green colour-when growing in milder climates. However, not all deciduous trees actually lose their leaves-some species of oak hang on to their dead, brown leaves until the growth of new foliage in spring. The part of the branch where the leaves were connected is sealed off by the growth of specialised cells. The leaves change colour, eventually turning brown and dry, then fall to the ground. They extract as many nutrients-mainly phosphorous and nitrogen-as possible from the leaves, to be stored in the woody parts of the tree and see them through the winter, and then cut their losses-literally. But it’s hard for broadleaf trees to keep their leaves healthy in these conditions, so many species don’t even try. Image adapted from: joronjubilee CC BY-NC-ND 2.0Įvergreen trees, like eucalypts and most conifers, have tough waxy leaves that can withstand the harsh conditions of winter. Deciduous trees lose their leaves to conserve energy during the winter months. Outside of the tropics, it also means cold-in many parts of the world, winter brings with it snow and ice. The shorter days mean there's less sunlight trees need to drive photosynthesis, which the trees rely on for energy. It’s time for deciduous trees to prepare for the harsh conditions of winter. Although here in Australia our natural landscape is dominated by evergreen eucalypts, part of the legacy of European settlement, particularly in urban environments, is gardens and streets lined with deciduous trees native to the northern hemisphere.Īs the days get shorter, the reduced amount of light signals that a change in season is well and truly on the way. And the trees (the deciduous ones, anyway!) know it, too. Yup, here in the southern hemisphere, it’s autumn. A chill has crept into the early morning and we’re pulling on an extra blanket at night. ![]() The days are getting shorter, the long warm summer evenings are pretty much done.
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