A heavenly green spectacle is spreading northwards across the country as trees open their new leaves. The delicate green of tree leaves in spring is remarkable and perhaps the greatest spectacle is the flush of new beech leaves that are so translucent they cast a green glow across woodland floors.

This green colour comes from the chlorophyll pigment in the leaf chloroplasts, the tiny cell bodies that perform photosynthesis. As the young leaves are still developing their chloroplasts, the leaves tend to be a lighter green. The new leaves are also thinner, with fewer waxy or tough layers, making them more translucent. What’s more, the leaves look brighter because they tend to have fewer additional pigments other than chlorophyll, so the green colour can shine through more clearly. But this is only a passing phase before the leaves turn darker green as their chloroplasts mature and the leaves grow thicker and more opaque.

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Another striking feature is how the trees in springtime have been tending to come into leaf earlier over recent decades, and that reflects how average spring temperatures across the UK have risen by about 1C over the last few decades. Spring even moves up the country faster for many plants and animals, averaging 1.2mph between 1891 and 1947, and 1.8mph between 1998 and 2014.