why do some trees have all dark red leaves (even in summer)
im sure they have chlorophyll also under the rust pigment
but i wonder if it's known what evolutionary advantage is provided by the heavy red pigmentation


Hello Feiv,

As far as I am aware it is not an advantage for the tree to have red leaves. The reason for it is a mutation resulting in a missing enzyme. An example for a tree with red leaves is copper beech. The enzyme normally removes the plant pigments which can be found in the epidermis of young leaves. The one which is not removed in the red leaves is called Anthocyane is used to absorb UV-radiation. As the Anthocyane is not decomposed the epidermis of the leave is not see-through but red or reddish. Therefore the green of the leaf inside does not shine through. Throughout the growing period the red coloring is lost and the leaves appear green.


Just to add a little extra to the story, copper beech is a good example of a mutation that has been selected for by horticulturalists because it makes a pretty tree, not because it has any advantage to the tree itself. In fact, the red colouration makes photosynthesis much less efficient, so the tree can't tolerate any shade. Look carefully at where you see them growing - usually in gardens or parks, never beneath any other vegetation.