generate their own sugars by photosynthesis,
making use of carbon dioxide that its enclosed
seeds give off as they grow. After they’re
harvested, the green pods continue to send
sugars to the seeds, so they lose their
sweetness. We eat the green seeds of many
legumes, notably lima beans, fava beans, and
soybeans (chapter9), but the pods of only a
few: the common bean, long bean, and pea.
Green Beans Green beans come from a
climbing plant native to Central America and
the Andes region of northern South America.
Though the peoples who domesticated them
have probably always eaten some immature
pods, the breeding of specialized vegetable
bean varieties is less than 200 years old. There
are now chlorophyll-free, yellowish “wax”
varieties, and purple, chlorophyll-masking
anthocyanin varieties that turn green when
cooked (p. 281). The fibrous “strings” that
normally join the two walls of the pod and are