Red anthocyanin is plant antifreeze

It's a flush of chemical craftiness 

Young rose foliage is gorgeous. See the deep red? That comes from a concentration of chemicals called anthocyanins, which are protection against cold. This emerging rose leaf can handle a great deal more cold than one on the flowering branch (below) that developed in warm weather and is all-green.

Other plants develop maroon in leaves, buds and even twigs in spring and fall. Now that you know about it, you can watch for it and admire those plants for their clever ways.

Right: Like this photo? You can buy it!

Below: There's enough red in a rose petal to melt a gardener's heart, but its summer chemical mix is not such a powerful antifreeze as what makes the spring foliage maroon.