Plant Families: Fabaceae (part 1)

I’m going to start the plant family discussion with the most marvelous of all families – Fabaceae (legumes). Not only are beans a very healthy food choice for us, they’re a healthy choice for your soil.

Legumes can, in a sense, pull nitrogen from the air and “fix” it in the soil. They’re not doing this incredible magic trick alone. The plant works with Rhizobium bacteria that live around the roots of the plant. Most soils in Minnesota have adequate amounts of these soil bacteria but you can also purchase powdered Rhizobium to pre-treat your seeds to ensure that the legume is doing its nitrogen-fixing best. In the Longfellow neighborhood where I live Mother Earth Gardens carries legume inoculant (a fine powder that you use to coat the seed prior to planting). Be sure to tell the staff if you are planting beans or peas; they use difficult inoculants.

So how does this nitrogen-fixing work to benefit the soil? When the plants are used as “green manure” and left on the garden to decompose, their nitrogen stores are released back into the soil. If you compost the plants, those nutrients become part of your compost pile, available for use when you add compost into your garden.

In organic farming, legumes are planted in rotation – two years of other crops, one year of a legume crop. You can easily do this in your home garden, too. Just remember where you planted your legumes.

Many legumes grow really well in Minnesota. Crops you may plant include:

  • Beans (hundreds of varieties)
  • Peas
  • Peanuts (YES, one variety can grow in Minnesota and you’ll find it at the Friend’s School Plant Sale)
  • Clover (Dutch white clover makes a lovely low-maintenance ground cover interspersed in your grass; it fixes nitrogen for your lawn and provides a tasty food for bees)
  • Lupines – although they aren’t edible, these gorgeous spikey purple flowers also fix nitrogen (see interesting blog post about that here)

My favorite purple pole bean

It’s Easy to Go Overboard with Beans

It’s easy to go overboard with beans and I usually do because I love to see the profusion of flowers on my favorite bean vines – a purple podded pole bean. Before you plunk down money for seeds, ask yourself four questions:

  1. How will beans fit into my overall garden design?

If you’ve got ample space specifically geared toward food production, a sea of bush beans will have a neat appearance. You can add a bit of pizzazz by choosing snap beans with yellow, purple or striped pods for a colorful garden. (Unfortunately, they lose their color after cooking.)

If you have less space, consider a pole bean on a bean teepee or a trellis. Beans can grow quite tall if given a chance so don’t plant any sun-loving vegetables behind them. You might lean a trellis against the house to provide shade from summer sun. I do this and then harvest them from behind the trellis.


Pole beans

  1. How often do I get out in the garden?

Some beans need to be harvested a couple of times a week or they will become fibrous and not good to eat. KNOW YOURSELF and be realistic. If you’re a lazy gardener (nothing wrong with that), dried beans are a great choice.

  1. Does my family regularly eat or can beans?

A couple of pole bean plants can produce ample green beans for fresh eating and will continue to produce for many weeks.

A row of knee-high bush beans will give you a flush of green beans (also called snap beans or string beans) all at one time. If you love canning dilly beans, bush beans are your best bet.

  1. How much space am I willing to devote to my bean passion?

If you love dried beans for meals – and who wouldn’t; they are a great source of fiber, full of resistant starch that helps lower cholesterol, they have a tremendous shelf life and the seeds are easy to save – you’re going to need a lot of garden space.

You’ll need a lot of plants in order to harvest a pound or more of beans. And you’re going to need to leave those plants in the ground for an entire growing season before you have anything show for your effort. Dried beans are harvested after the plant has died and dried out.

How do you know when the bean is dry enough? Open up the pod and remove one seed? Try to bite into it: beans that barely dent when bitten are the right level of dryness. Don’t eat it! Dried beans need to be cooked … read further down the page to learn why.

Planting Beans

Most beans like the soil to be at least 60°F when you plant the seeds or seedlings. Bean seeds will rot in cold, wet soil so don’t jump the gun by planting too early. You can start seeds indoors if you have grow lights.

Many beans grow well here but I’ll draw your attention to a couple of cool-season beans that you might not have considered before: chickpeas and fava beans.

  • Chickpeas (garbanzo beans) are not technically a bean or a pea – what they are is finicky. I haven’t tried to grow them … I’m not sure I will. Chickpeas are frost tolerant but they need 100 days to harvest and they prefer daytime temps around 70 to 80º and night time temperatures above 65ºF. These plants hate to have their roots disturbed. Sow them indoors in a paper pot. Don’t soak the seeds or overwater them; the seeds will crack. Transplant the pot and plant into the garden when the plants are 3 to 4 inches tall. Be careful when weeding so you don’t disturb the roots. A high nitrogen soil is going to reduce production so don’t add a nitrogen fertilizer. Don’t use overhead watering; do Chickpeas are susceptible to an array of pests and disease. If you do plant it, be sure to rotate the crop every 3 years to avoid soil-borne disease. Don’t interplant with garlic.
  • Fava beans are a cool-season crop that grow best in temperatures from 60° to 65°F, but they will grow in temps as low as 40°F and as warm as 75°F. Sow fava beans as soon as the soil can be worked in the spring. They take 80 to 100 days to reach harvest. I know people who have had great success with fava beans in my neighborhood.

Food Safety Note for Beans

A number of dried beans, for example red kidney beans and white beans (cannellini), contain toxins. This is not a problem if prepared properly. Dried beans must be thoroughly cooked; remember to leave yourself time to soak them. Dried beans should not be sprouted. Read up on the best way to cook the beans you are considering planting so you’ll know how to cook them right.

Soybeans are tricky beans. They contain an enzyme that prevents the digestion of proteins. Do NOT eat soybeans raw. I’m not a food scientist so I’m not going to tell you exactly what to do – I’m just going to say, DO YOUR RESEARCH. Soybeans are particularly problematic. Fermentation is probably the safest way to process soybeans – it’s the traditional way of using them.

Home-canned beans are one of the most common sources of botulism food poisoning. If you are canning beans you must use a pressure canner. Beans pickled with vinegar contain enough acid to be safe to can with a hot-water bath canner so if you followed the recipe, you should be safe with those home-canned dilly beans.

Note that the USDA has reviewed and revised canning recipes and instructions in recent years. If you are canning from on your mother’s or grandmothers’ recipes and instructions, you may be at increased risk of food-borne illness. Check out the National Center for Home Food Preservation for new instructions.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s