Color and shape of maple leaves in four seasons. Thank you.

Maple leaves are green in spring and summer and turn red and yellow in autumn (depending on the anthocyanin content in maple leaves). There are many kinds of maple trees in China, such as Cotinus coggygria, Acer truncatum and Sapium sebiferum. Because of the different leaves of tree species, there are fifty or sixty species, such as triangle, pentagon, heptagon, chicken claw, duck claw and so on.

The internal cause of maple leaves turning red in autumn is the chemical reaction between anthocyanins and acidic fine liquid, and the external cause is that the weather turns cold after autumn, which promotes the increase of anthocyanins, that is, the change of meteorological conditions.

Therefore, it is the level of climatic conditions in autumn that dyed it red. There is no fixed time because of external uncertainty. When the temperature and humidity reach a certain level, it will turn red, but it usually turns red in early September of the lunar calendar.