Asterids are a very large a very diverse group of organisms. Species of asterids occur in most terrestrial habitats on Earth, and grow under many different conditions. There are some that grow as small herbs, some that are climbing vines, some that are shrubs, and even some sizeable trees.
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Asterids great and small : Asterids come in all shapes and sizes. At left, Lactuca serriola, a wild species of lettuce and a spindly roadside weed. At right, the spectacular flowering tree Paulownia tomentosa, from Hunan Province in China.
Many species are important food crops (e.g. carrots, potato, sweet potato, lettuce, tomato, sunflowers), but many others produce toxins to discourage animals from snacking on them. Many members of the potato family are quite toxic (such as nightshade), as are some members of the periwinkle family (e.g. oleander). Hemlock has become infamous as the poison that killed Socrates, and it too comes from an asterid (in the carrot family). However, one species of periwinkle (Vinca) has also yielded a powerful drug used to fight cancer.
