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Free Fertilizer! How to Grow Fava Beans as a Cover Crop

Free fertilizer! How to grow fava beans as a cover crop

In winter, a couple of my garden beds get less sun and stay more damp so it’s difficult to grow a food crop. I usually let the soil rest at this time, but by that I don’t mean I leave the garden beds bare.

Even if you only garden three seasons out of the year, you should never leave the soil exposed and empty.

Winter rains could lead to soil compaction, especially in hard clay soils. The earth could erode, washing nutrients away if there are no plants and roots to reign them in.

Some people simply throw a layer of mulch on the ground and call it good.

But I like to grow a cover crop — and I especially like to grow fava beans as a dual-purpose cover crop.

Fava bean plants supported with wire tomato cages and bamboo stakes

Benefits of growing fava beans as a cover crop

As a legume, fava beans fix nitrogen in the soil; that is, they put in more nitrogen than they take out.

As a cover crop, they improve soil texture, suppress weeds, support microbials in the soil food web, attract pollinators with their abundant flowers, and they’re even edible to boot.

They are the gift that keeps on giving, and all you have to do is plant them, then chop them.

Fava bean stem with fava flowers

Fava beans are ideal plants for fall because they germinate quickly, thrive in cold weather, and are one of the few fruiting plants that tolerate shade.

They require minimum watering in winter, especially in wetter climates. And if your garden is less than perfect, rest assured that fava beans can easily be grown in deficient soil or clay soil (after all, their job is to make it better).

However, fava beans are happiest in rich loams with good drainage. At the very least, try not to let the plants stand in waterlogged soil for too long.

So even after knowing all this and thinking you don’t have the patience to shell fava beans, or you don’t like the taste of them… You should still grow fava beans as a cover crop (for your garden’s sake) and aim to get them in the ground between September and November, depending on the timing of your first freeze.

Related: Know When to Grow: A Planting Calendar For Your Garden

Broad bean leaves

How to plant fava beans in fall

Fava beans (Vicia faba, also called faba beans or broad beans) are actually not a bean but a type of vetch, a common cover crop and forage crop.

They’re cool-weather plants that should be sown directly in the garden in fall to enrich the soil for the following spring.

Though it isn’t necessary, you can soak fava bean seeds for a few hours to speed up germination. This is especially helpful if the weather is still dry when you plant and you want to ensure the seeds germinate.

Sow the seeds about 6 inches apart and 1 inch deep. Keep the soil consistently moist but not soggy.

Sprouts will appear that first week, and grow into 6-inch seedlings within a couple of weeks.

Broad bean seedling in the soil

Once they reach that height, add 2 to 3 inches of straw (or another organic mulch) around the plants, being careful not to pile the mulch against the stems (which could lead to rotting).

Aerial shot of fava bean plants mulched with straw

Fava beans are tall, thin, and top-heavy plants that require minimal staking as they mature so they don’t flop over under their own weight.

They’re well suited for those conical wire tomato cages that, ironically, don’t do a super job of supporting indeterminate tomato plants. But they’re fantastic for fava beans!

Worth a read: Grow Tomatoes Like a Boss With These 10 Easy Tips

You can also support them with bamboo teepees, or a combination of both for an aesthetically pleasing grouping.

A row of fava bean plants supported with wire tomato cages and bamboo teepees

Fava beans grow 3 to 6 feet tall and produce clusters of beautiful, orchid-like flowers. The flowers turn into dense green pods that sometimes reach 8 inches long or more.

Close-up of mature fava bean pod

With proper mulching, fava plants only need an inch of water a week, and sometimes less if they’ve had rain.

The leaves are susceptible to fungal rust, an airborne plant pathogen, so keeping them dry with good air circulation is important.

Like other legumes, fava beans do not need nitrogen fertilizer (assuming your soil is halfway decent — at most, you can amend with compost after you’ve pulled out last season’s plants).

They have the unique ability to work with the rhizobia in their roots to make nitrogen from the air, and over-fertilization may actually stunt production of the pods.

Artistic shot of fava bean flowers in the garden

When and how to turn fava plants into the ground

Once you’ve harvested all the beans (as well as the fava leaves and flowers, which are edible), you can prune the plant back to just a few inches above the ground.

Read more: 11 Vegetables You Grow That You Didn’t Know You Could Eat

I like to trim mine down to 6 inches, cutting just above the leaf nodes. This vigorous haircut, although a little scary at first, encourages new growth and you may get a second harvest of beans in the same season (especially if you choose an early variety that’s well adapted to your climate — see my recommendations in the last section).

Learn more: Days to Maturity: What It Really Means For Your Plants

Fava bean pods are still edible before they’re fully formed, and can even be eaten whole. So don’t worry if yours never reach their full mature size; the young pods are tender and delicious.

The following spring, after the last of your harvest, cut down all the plants but leave the roots to rot in situ (so they release nitrogen back into the soil).

At this stage, the stems are too woody to dig into the ground, so I simply compost all the stems and leaves.

Fava beans planted as a cover crop in the garden

How to use fava beans as green manure in spring

You can plant another fava bean crop in spring and repeat the process.

In mild climates, the seeds can be sown as early as late January. Fava beans grow best in daytime temperatures of 60°F to 65°F, so time your plantings accordingly in either season.

If you want to grow fava beans as green manure in spring (before you transplant heavy feeders like tomatoes and squash), cut down the plants at soil level while they’re in peak bloom. Dig them under a bit and spread a layer of mulch over the bed to maximize nitrogen retention.

(Note that leaving the decomposing plants near the surface provides slow-release nitrogen to new plants, while breaking them up and burying them several inches deep adds a quicker dose of nitrogen.)

Do the chop-and-drop about two to three weeks before you want to plant in the same spot. When your new seedlings are ready, you can just push the mulch aside to transplant.

Remember! Using fava bean plants as “free fertilizer” doesn’t mean you can skip fertilizer completely. But you may only need half as much nitrogen in an average season.

Live in a mild climate? Fava beans can be sown year-round in areas with Mediterranean-like weather (such as the California coast) where winters are warmer and summers typically don’t go above 75°F. (Between May and August, it’s best if your fava crop has some morning fog or afternoon shade.)

Close-up of broad bean flowers on a stem

Recommended fava bean varieties

Growing fava beans solely as a cover crop or green manure (with no intentions of harvesting for food) means you can buy cheaper seeds in bulk, rather than culinary varieties that are sold 25 seeds to a packet.

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Here are some recommended varieties to try, based on your needs and climate:

  • Small Fava: Forage-quality variety sold by the pound
  • Sweet Lorane (30 to 60 days): Extra early variety bred for cover cropping, cold tolerant down to the low teens (°F)
  • Extra Precoce a Grano Violetto (65 to 70 days): Early variety with purple beans
  • Windsor (75 days): Delicious and popular heirloom bean
  • Aguadulce (75 to 85 days): Very sweet and exceptionally cold hardy

This post updated from an article that originally appeared on October 15, 2013.

Linda Ly About Author

I'm a plant lover, passionate road-tripper, and cookbook author whose expert advice and bestselling books have been featured in TIME, Outside, HGTV, and Food & Wine. The No-Waste Vegetable Cookbook is my latest book. Garden Betty is where I write about modern homesteading, farm-to-table cooking, and outdoor adventuring — all that encompass a life well-lived outdoors. After all, the secret to a good life is... Read more »