Monday, June 6, 2011

Runner Beans: the Original Magic Bean Stalk

Scarlet Runner beans are mottled with pink and black
The Scarlet Runner bean has won a very special place in my heart. It is lovely as a trailing ornamental garden plant, and also provides delicious edible pods and beans. Another wonderful quality of runner beans is that they are also a perennial vine, meaning beans will grow all year round  in mild climates, and do not have to be resown. In our area (hardiness zone 9) the beans die back with the first frosts of winter, then reemerge in the spring.

Runner Beans versus Common Beans
These legumes are able to do this because runner beans, P. coccineus, are a different species than the so-called common bean, P. vulgaris (cranberry bean, pinto bean, etc.). Runner beans develop large starchy underground tubers and common beans don’t. Another big difference is that runner beans like mild summer temperatures and they won’t set pods in hot climates, but you will have the attractive vines and flowers. To get pods they should be protected from the hottest afternoon sun where summer temperatures are very warm. 

In my zone 9 (USDA scale) climate on the San Francisco Peninsula, they do fine with temperatures in the 70's to 80's (degrees F) with occasional spikes to the 90's as long as I keep them watered and avoid trellising them on a south or west facing wall.

Scarlet Runner flowers - these are growing in a pot in my backyard
There are other varieties of runner beans besides the popular Scarlet Runner: purple, black and white runner beans are also available (the color refers to the seeds, not the flowers, unlike the Scarlet Runner). Runner beans in Nahuatl is “ayocotl” or in Spanish “ayocote“. The Ayocote Morado is the purple runner bean. I have grown two different white runner beans,  the Italian Butter and Gigante, both from Iacopi Farms in Half Moon Bay, CA. These white beans tend to have large pretty white flowers.

What's in a Name?
Be forewarned that the term "runner bean" is sometimes used for any bean that climbs. In my experience, "runner bean" is usually used for P. coccineus, but remember that it's not reliable. It's alway best to look for the botanical name on a seed packet just to be sure. And although I grow a type of Gigante bean that is clearly  P. coccineus, I have seen Gigante listed as  P. vulgaris. This just means that somewhere along the way the same common names have been given to different beans- just to keep things interesting!

These beans originated in the Americas, and were introduced into Europe from the New World, where other cultivars were developed, such as the Italian Cannellini Runner and the Greek Gigante, the French Flageolet, and many others. They've traveled back to the Americas bringing their culinary histories with them as part of the cultures that have embraced them as their own.

Gigante beans
Runner or Common Bean? Here's a Simple Test
Try this test to find out if you have runner bean seeds: sprout the bean in some soil. When a common bean germinates, the cotyledon emerges above the ground (these are embryonic leaves which are the halves of the seed- see photo below) and the true leaves develop afterward. If it’s a runner bean the cotyledon will stay in the ground and the true leaves rise up directly out of the soil.
A common bean (P. vulgaris) seedling with the cotyledon
Runner Beans as Perennials
So what are the implications to the gardener? You can plant runner beans in a permanent spot in your garden where they will trellis up 7-10 feet as beautiful lush vines with pretty flowers that attract hummingbirds and bees. When the vines die back with frost, cut them at ground level and just mulch over the roots. They'll emerge again in spring.  If you live in an area where the ground freezes in winter, you might try digging up the tubers and storing them somewhere where they won’t freeze, then replant them in early spring.

Saving Seeds
If you want to save the seeds simply let the pods dry on the vine then shell them and store in a dark, cool dry place. Runner beans tend to cross pollinate easily with other runners (P. coccineus), but not with common beans (P. vulgaris), so to save seed that will be true to the type you originally planted, you’ll have to cover them with a protective mesh before the flowers open to keep out aggressive pollinators like bumble bees, that seem to love these flowers. Beans are self pollinating, but to be sure you get pods you can "trip" the flowers by pulling on the lower lip. But if you grow them from the tubers left in the ground this will not be an issue.

Seed Savvy
For an excellent reference on saving seeds from almost any vegetable you can think of, refer to the book Seed to Seed by Suzanne Ashworth, published by Seed Savers Exchange.
Besides instructions on seed saving, her book includes descriptions of the botanical families of edibles and which types will cross hybridize, and much more.

Note: this post was updated July 2014

Photos: Patricia Larenas, Urban Artichoke


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