Scarlet Runner Beans

Q.  I have been looking for some guidance in planting scarlet runner beans. I life in San Clemente, do they grow well in this area? Should they be planted in fall like Fava Beans? Or treated like regular snap beans and planted in the spring?

A. Now about scarlet runner beans: Be of good cheer, you have not missed the time to plant. March is best, especially this rainy year that could rot beans in cold heavy soil. Here’s the explanation: All beans are members of the pea family (Fabaceae, Leguminosae). Most of the edible bean species we grow in our gardens are native to the New World, and the majority of these fall into the Phaseolus genus, which is a group of warm-season beans that include our common pole beans and bush beans, also called green beans, string beans or snap beans (Phaseolus vulgaris)—All these ones are annuals we plant in spring and harvest in late spring through summer.

Scarlet runner bean (Phaseolus coccineus), is also a warm-season bean, but it differs from P. vulgaris in that, though it is usually grown as an annual, it is actually perennial and also the cotyledons stay in the ground while the seed germinates, unlike green beans which will pop up out of the ground pretty quickly as soon as the seeds germinate.  Fava beans (Vicia faba) are not related to scarlet runner beans. They originated in the Old World and they are cool-season crops. In warm-winter climates such as Southern California, we plant cool-season crops in fall and harvest them in winter and spring.

Being a warm-season crop, scarlet runner beans are best planted after the weather has warmed up in spring. Early March is the best time to put these seeds in the ground here. (To plant and grow scarlet runners, follow the step-by-step method for runner beans or pole beans in my book, including putting the seeds in the ground with scar side facing down.) Scarlet runner beans are often grown as an ornamental.

If you plant the seeds in March they will quickly cover a trellis, screen a porch, or fulfill any other job you might have for them and bring hummingbirds to boot. You can also eat their beans as a cooked vegetable. Pick them when they’re very young and tender, otherwise they will be woody and inedible, but if you accidentally let some overgrow, you can shell them and eat the bean inside like limas.

Always cook all green beans since raw ones contain a slight amount of poison, not enough to kill you but still not a good idea. It really bothers me when I see people eating beans raw and offering them to children, especially fava beans since they contain more of a toxic dose. (The poison is a lectin, or sugar-binding protein, called Phytohaemagglutinin; people who doubt me can look this up if they want.) But if you cook them, it’s absolutely fine to eat scarlet runner beans as a vegetable and you don’t have to over-cook them either. You can eat them when they’re barely tender but still crunchy and meanwhile you can enjoy the lovely flowers and scads of hummingbirds they will attract.