Butter beans, sometimes called lima beans, are a seed, and are considered a vegetable. They are of the genus and species Phaseolus lunatus, and have two main varieties. The first variety is a large slightly curved flat green bean that those in the Southern US would refer to as lima beans or the lima type. A second type of P. lunatus has smaller seeds and is often called the sieva type. When Southern US cuisine mentions butter beans, they are referring to the smaller sieva seed.

The lima bean appears to have first been cultivated in the Andes, while the smaller butter beans were more commonly grown in Mexico. Both styles are grown harvested from seedpods, where in fresh form they’re commonly green. There are some variant colors, among them red and orange. Because they are usually picked before ripening, you’ll find most “fresh” beans in a green color. The smaller lima beans are about .4 inches (1 cm) long, and larger variety lima beans can be about 1.18 inches (3 cm) in length.

There are slight differences in nutritional value between butter and lima beans. Butter beans have tiny amounts of fat, are higher in iron, and are slightly higher in calories. Both types of beans are excellent choices though. While you can find butter beans dried, frozen or canned, they are most preferred as a fresh vegetable side dish. They take about 20 minutes to steam, and are usually served with a pat of butter and a little salt/pepper and herbs.

You can find fresh butter beans in the US from late spring through the early parts of summer. Since they are popular, both versions of the bean are grown in other countries and may be imported at other times of the year. You can also usually find frozen butter beans, which make a good substitute when fresh beans are not in season.

In Northern US grocery stores, you’ll have better luck looking for lima beans, since quite frequently, butter beans is strictly a southern cooking term. Either large or small lima beans can make for lots of interesting dishes, and needn’t be restricted as merely a side dish. A lima bean casserole makes for a hearty vegetarian dish, and can easily be cooked in a crock-pot. Lima beans may be added to soups, to salads, or to a variety of other dishes. In the south, there are even many recipes for butter bean pie, which has a similar consistency and flavor to sweet potato pie.