Lima Beans

Lima beans have the ability to poison their attackers, and groups of lima bean plants work together to counteract threats caused by caterpillars. The world of plants never ceases to amaze me.

Lima beans (Howard F. Schwartz, Colorado State University, bugwood.org) CC BY 3.0

The lowly lima bean, hated by many, loved by some, is a legume. These particular legumes put out chemicals that attract parasitic wasps whenever caterpillars start chewing on their leaves. The wasps lay their eggs in the caterpillars, hatch, and devour their host. Lima beans also contain certain chemicals, stored in different parts of the plant, that become activated when the seeds are chewed, creating potentially fatal cyanide poisoning.

​Before the Lima Haters shout a resounding, “We told you so!”, it is important to note that cooking lima beans for at least 10 minutes eliminates those chemicals. So, in the case of lima beans, simply soaking isn’t good enough. You need to put them to the fire before eating.

​Why grow lima beans?

Despite childhood trauma and potential poisoning, lima beans (Phaseolus lunatus) are actually a very sweet, high fiber source of protein, folic acid, iron, manganese, and potassium. Even better, they are easy to grow and excellent additions to balconies and windowsills, as well as standard gardens. You can select bush or pole varieties. (Sometimes the smaller bush varieties are called butter beans, if that makes them more palatable.)

​How to grow lima beans

Lima bean plants will not put out pods in temperatures above 80°F or when it’s cold and wet, so spring and fall are the best times to grow lima beans. Seeds will take 60 to 90 days from planting, so plan accordingly. (Bush varieties take 60 to 80 days; pole varieties take 85 to 90 days). Lima beans prefer a soil pH of 6.0 to 6.8 and full sun, but they can handle partial shade, especially as summer temperatures rise. Surprisingly, too many nutrients in the soil will cause your lima bean plants to produce lots of vegetation, and not very many beans, so you can forego the aged compost. Also, too much water simply makes the beans split, so water sparingly. Plant seeds 1-1/2 to 2 inches deep. Bush beans can be planted 6 inches apart - the plants will actually help hold each other up. Pole beans should be planted 10 inches apart and be sure to provide them with a trellis, tomato cage, fence, or balcony to climb. Pole beans can reach 10 to 12 feet in height. If you need to thin your bean plants, simply cut them off at ground level. The roots have a symbiotic relationship with soil microbes that “fix” atmospheric nitrogen into the soil, feeding nearby plants.

Lima bean pests and diseases

Beans are commonly attacked by aphids, flea beetles, bean beetles, mites, and leafhoppers. Plus, those aphids can carry the bean mosaic virus. Other lima bean diseases include blight and anthracnose. Beans are also susceptible to many diseases found in the soil, so crop rotation is a good idea.

Dried, ripe lima bean pods

California is responsible for 60 to 80% of the world’s lima bean crop. You can be responsible for 100% of your lima bean crop by growing your own!