Often times after planting a new tree, including chestnuts, oaks and beeches, you may notice that new flushes of leaf growth have a red or purple coloration, rather than the typical green.
In the above image, you can immediately differentiate the red coloration of the small new leaves, compared to the lush green of the older oak leaves. This is an entirely normal occurrence, and in fact beneficial for the young tree. Deciduous tree leaves are generally various shades of green, as this is the prominent visible coloration of the photosynthesizing chloroplasts contained within. The newer leaves meanwhile have some green color, but also have significant tinges of red throughout.
This red, or sometimes purple, coloration is caused by the production of anthocyanins within the leaves. Anthocyanins are flavonoids, or more specifically pigments, which contain natural properties that help to protect the newly emerging leaves. Newly emerging leaves are not acclimated to the harsh sunlight, which can damage tender foliage. Anthocyanins seem to be especially prominent in the young foliage of trees within the Fagaceae family, such as Oaks, Chestnuts and Beech. Hornbeam as well often displays this trait.
Anthocyanins work almost as a natural sunscreen or protection for the leaves, by absorbing some of the more damaging wavelengths of light, thus protecting the green chlorophylls which absorb solar energy for use in photosynthesis. Studies have also shown that anthocyanins help to prevent photo-oxidative injuries by collecting free radicals in the leaves. Additionally, through both anecdotal observations as well as more rigorous scientific studies, the red and purple tinted leaves appear to be eaten significantly less often by insects, herbivores and other pests.
So while often one may be concerned by the strange purple and red color appearing in their young oak tree’s leaves, it is nothing harmful whatsoever and is in fact indicative of properly working protective mechanisms within the tree.
