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What Are Legumes?
The legume family (also known as Leguminosae or Fabaceae) includes a large and diverse group of edible plants that are primarily used as food and cover crops.
Plant species within the legume plant family include grain legumes like:
- Peanuts (Arachis hypogaea)
- Peas (Pisum sativum)
- Common beans (Phaseolus vulgaris)
- Cowpeas (Vigna unguiculata)
- Broad beans (Vicia faba)
- Chickpeas (Cicer arietinum)
- Soybeans (Glycine max).
Grain legumes have very high nutritional value and are a great source of protein and fatty acids.
In addition to growing beans for human consumption, farmers plant legume species to enrich soil with nitrogen during crop rotation. Some species of vetch legumes, specifically hairy vetch and milkvetch, are an effective form of erosion control.
How Do Legumes Fix Nitrogen in the Soil?
Legumes have evolved in symbiosis with nitrogen-fixing bacteria called rhizobia that live on their root nodules and possess the almost miraculous ability to convert atmospheric nitrogen into a soluble form that roots readily absorb. This is known as nitrogen fixation.
Nitrogen is the element responsible for lush green growth in plants, but it is in short supply in most soils, which is why farmers and gardeners often add manure, inoculants, or synthetic fertilizers. Beans and peas add nitrogen to the soil, replacing the nutrients consumed by harvested non-legume crops. Beans and other nitrogen-fixing cover crops are sometimes referred to as “green manure” because they enrich the soil around them even after they have withered or been uprooted. Cover crops like legumes are essential for restoring degraded soils.
3 Common Types of Legumes
The legume family is incredibly diverse and includes plants that vary in appearance, taste, and growth cycle. Many legumes produce a dry fruit that serves as food for humans or livestock, including alfalfa, buckwheat, carob, tamarind, and lentils. Some of the most common types of legumes include:
- Peas: Common peas include garden peas, green peas, cowpeas, chickpeas (garbanzo beans), pigeon peas, and black-eyed peas.
- Beans: The abundance of common beans in the legume family include: adzuki beans, mung beans, lupine beans, black beans, green beans, kidney beans, lima beans, fava beans, and broad beans.
- Clover: Red clover, white clover, sweet clover are common cover crops.
How to Grow Legumes: 8 Tips for Growing Beans and Peas
Legumes grow vigorously with minimal effort. Most legumes are hardy, durable crops that are easy to maintain and harvest. Here are some general tips for growing legumes:
- Make sure legumes are suited to your climate. Different species of legumes vary in terms of their ideal temperature range. Peas do well when planted in late spring and will stop growing in the summer months. Green beans, on the other hand, can tolerate a large temperature range and will grow when the air temperature is anywhere between 65 and 85°F.
- Plant legume seeds the right distance apart. Most legume seeds (including bean seeds) thrive when planted between six and 12 inches apart from each other. Some legumes, like lima beans and peas, can grow on trellises.
- Grow legume crops in direct sunlight. Legume plants do best in unshaded areas, arranged so that they don’t block each other from receiving sunlight.
- Keep the soil moist. Most plants in the legume family do well in moderately moist soil with average soil fertility. Adding mulch or organic matter can help preserve soil moisture and keep soil temperature down for peas and green beans.
- Water your legumes consistently. Legumes do well with a consistent amount of watering, especially as temperatures rise. Green beans require one to two inches of water per week and do well with in-ground irrigation systems, as opposed to hand watering from above. Peas don’t mature in waterlogged soil, but pea seeds should be soaked in water prior to planting.
- Fertilize sparsely. Most legumes do not need extra fertilizer added to the soil. Some legumes with longer growing seasons, like lima beans, benefit from soil amendments and extra manure added midway through their life cycle.
- Control pests. Common garden pests like aphids and beetles often prey upon legumes. Some of these pests can spread plant diseases that ravage your crops if you don’t catch them early enough. It’s important to proactively inspect your plants to look for signs of pests. Choose the right method to fight infestation.
- Harvest at the correct time. There’s a wide range of season lengths for different types of legumes. Keep a watchful eye on your crops to look for sprouting, and be sensitive to sudden temperature changes that might affect the health and maturation of your legume plants. If you plan to eat your beans or peas fresh, pick them when the pods are still tender. Otherwise, allow the pods to mature, and harvest them when they’re dry.
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