LEAVES IN AUTUMN

Press, Volume CII, Issue 30093, 29 March 1963, Page 7

LEAVES IN AUTUMN

Last Burst Of Colour Autumn' is already with us for the nights are drawing in and there is a distinct nip in the air. One feature which always brings autumn to our notice, is the changing colours of the leaves of deciduous trees and shrubs. The rather commonplace green gives way to a variety of brilliant shades as the trees concerned give one last burst of colour before they retire to dormancy for the winter. Colours vary from the palest gold to the most intense and fiery scarlet. Landscapes planted with deciduous trees assume a beauty before the winter, in complete contrast to their rather ordinary appearance that is to be seen for most of the year. One has only to think of the golden colours of the poplars of South Canterbury and Otago at this time of the year to realise how true this is. Autumn colours turn poets to raptures, but I wonder how many people know just why a plant takes on these different and colourful shades at this time of the year? At the end of the growing season the trees withdraw from the leaves anything that will be of use before the leaves fall. The useful substances are mainly sugars and to assist in this work other accessory materials are used. Some are colourless and their presence is unnoticed but in others, a substance known as anthocyanin comes into use. This may be blue, purple or red according to the acidity of the cell sap. During the process of removal there is a gradual change in the green colouring matter until all that is left, in the absense of anthocyanin, are yellow grains. If these grains are few the leaf quickly turns brown and withers. If however, they are plentiful, the leaf assumes the yellow colouring that is associated with the poplars. When these yellow grains are associated with anthocyanin the leaves develop orange, red and purple tints. These conditions vary with different plants and under different atmospheric conditions. Trees exposed to ample light take on the most intense colour. The amount of sun prior to leaf fall and the alternating temperatures between day and night are also important. Colouring is always most spectacular in the cooler parts of New Zealand. While some herbaceous plants such as peonies exhibit autumn colour, it is most commonly associated with trees and shrubs and in fact we plant some of these in our gardens solely on this account Some of the best include most of the maples, the birches, poplars, deciduous azaleas, some of the deciduous oaks, tulip tree, ma idenhqi r tree, many flowering cherries and of flocuns Liqujdambnr.