Some of the loveliest harbingers of a Midwest spring are crabapple trees. They bloom so prolifically you almost can’t see the branches through the cotton-candy clouds of pink and white. But these trees have other assets. Summer through fall, their foliage can be glossy green, bronze, or purple-tinged. The fruit they produce is too bitter for snacking but is tasty in jam or can be left on the tree to soften and provide cold-weather food for songbirds.