If you're from the South, you may know cowpeas (Vigna unguiculata) as black-eyed peas, and you may enjoy them as a New Year's treat, but these protein-rich legumes aren't native to North America. They grow in sandy soils, and west Africa, which produces 65 percent of the yearly global yield, has plenty of sand, as do Kenya, India and Brazil, where it's also an important crop. The cowpea was domesticated in East and west Africa as early as 2500 BCE, and peas came to the New World on slave ships, where they were used to feed the hungry passengers. From Jamaica, domestication in the New World followed the slave migration to Mexico, South America and the American South, and because the plant grows only in warm climates, those in the South have been the main beneficiaries, which is why cowpeas are also known as Southern peas.
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The cowpea plant can grow as a bush or a vine, so you'll want to make sure you know which variety you are planting so you can space the plants accordingly and supply support if needed. Both bushy and creeping cowpea plants have lush, green leaves, which are edible and make a good addition to salads. Yellow flowers precede the production of long, narrow cowpea pods, which are reminiscent of green beans, and each pod contains several peas crowded closely together, which is the probable reason they are also called crowder peas. The peas are typically ready for harvesting 60 to 100 days after the seedlings emerge.
Cowpea plants do not tolerate frost at all, and they thrive in regions where the temperature exceeds 85 degrees during the day — in fact, the hotter the temperature, the happier the plants. They are famously easy to grow and are a good crop for the beginning gardener, especially given the high nutritive value of the peas and the leaves. Planting cowpeas presents few downsides, but if you discover one, don't worry. It's an annual, so you can always plant something else the following year, and that could actually turn out to be a good strategy because cowpeas add nutrients to the soil rather than depleting it.
Best Uses for Cowpeas
Like beans and other legumes, cowpeas metabolize nitrogen from the atmosphere and fix it into the soil through their roots, so cowpeas are a good rotation crop for tomatoes, okra, muskmelons, squash and other vegetables that need extra nitrogen. The cowpea plant continues fixing nitrogen in the soil right up until it goes to seed, and it isn't fussy about soil quality, so farmers often grow cowpeas as a cover crop in poor soil. After harvesting the peas, they plow the plants directly into the soil and let them function as green manure, filling the soil with nutrients as they decompose and setting the stage for a different crop the following year.
Because the peas and leaves are both edible and nutritious, cowpeas can be part of an edible landscape. Besides being tasty, the leaves are lush and green, and the snapdragon-like flowers add their own charm and color to the garden. Creeping up a trellis, the vines offer shade to low-growing plants that need it, which is a useful function in the subtropical climates that cowpeas prefer.
Because it grows reliably in almost any type of soil, is drought tolerant and is so full of nutrients, the cowpea has historically been a mainstay fodder crop. That's great if you're a cattle breeder, but it's a minus if you're worried about deer because they like the leaves as much as cattle. You'll have to make special efforts to keep the deer away when you include cowpeas in your landscape design.
How to Grow Cowpeas
- Common Name: Cowpeas
- Botanical Name: Vigna unguiculata
- When to Plant: Plant in mid-April in the South and late May to early June in Northern regions
- USDA Zones: 3-11
- Sun Exposure: Full sun
- Soil Type: Sandy, loamy soil with good drainage and pH of 6.0 or higher
- When it's in Trouble: Root rot and damping off will kill young cowpeas planted too early in the season
- When it's Thriving: Lush, green leaves; delicate blossoms; long, plump seed pods
Starting Cowpeas From Seed
Because they grow so well outdoors and do not like to be transplanted, cowpeas are usually direct-seeded into the garden. The plant doesn't have any stringent soil requirements, so it usually isn't necessary to add nutrients, particularly nitrogen, which it fixes into the soil itself. To maximize nitrogen production, it's a good idea to treat the soil with a bacterial inoculant prior to planting and to turn the soil to a depth of 8 inches with a hoe to get rid of weeds.
Sow seeds 1 to 1 1/2 inches deep by making a hole for each seed with your finger, dropping in the seed and loosely covering it with dirt. In heavy soil, it's a good idea to create a raised bed or row for the seeds to allow water to run off and to prevent damping off or root rot, which are two diseases that commonly affect cowpea plants. When planting a bush variety, sow seeds 2 inches apart in rows separated by 3 feet, and when the seedlings emerge in about 10 to 12 days, thin them to increase the separation to 4 inches. When planting vines, increase the spacing to 10 to 12 inches.
In What Zone Do Cowpeas Grow Best?
Cowpeas aren't known as Southern peas for nothing. Originating as they do in Africa, they prefer warm climates and grow best in USDA zones 9 to 11, where the air and soil are consistently warm. Cowpeas are drought-resistant and are a good crop for gardeners in the semidesert regions of the American Southwest.
Growers in Northern regions need a growing season of at least 60 to 100 days, and the soil temperature must be consistently above 65 degrees Fahrenheit with no danger of frost. Although cowpeas don't tolerate transplanting, they can be grown in large containers with appropriate support structures that can be moved indoors to lengthen the growing season.
When Should You Plant Cowpeas?
In Southern regions where frost isn't a concern, seeds can be sown as early as April, and they can be resown at two-week intervals through the summer to ensure a continuous harvest. In Northern regions, it may be necessary to wait until June to sow seeds, and since the first frost can come as early as October, the growing season probably isn't long enough to accommodate multiple plantings.
Soil, Sunlight and Water Recommendations for Cowpeas
Cowpeas have a remarkable ability to grow in any type of soil, but they prefer sandy or loamy soil that drains well. They don't need extra nitrogen because they produce their own, but they can benefit from a phosphorous-rich fertilizer. The bacteria with which they form a symbiotic relationship to produce nitrogen are present in most soils, but many growers inoculate the soil anyway as a safeguard.
Locate the cowpea plant in a part of the garden that receives full sun because it needs six to eight hours of direct sunlight a day. Although it's drought-resistant, it prefers an inch or so of rainwater every week, so in regions that do not receive that much rainfall, the plants should be watered whenever the soil dries out, especially in the week or two before harvest. Avoid overwatering because excess moisture cools the soil, but if soil conditions are particularly dry, they will benefit from an application of mulch to retain heat and moisture in the soil.
How to Propagate Cowpeas
The only way to propagate cowpeas is by seeds, and to get these, all you have to do is pop a few peas in an airtight container before cooking the rest. You can harvest seeds that you plan to eat anytime they are ripe enough, but seeds for growing should remain in the pod until it has dried out on the plant.
The seeds are like dry beans, and if you store them in a cool place, they will keep for three to four years. Just before sowing them, it's a good idea to soak them overnight in water to stimulate germination.
How to Winterize Cowpeas
The cowpea plant won't tolerate frost or cold temperatures and will die off in the winter. A good way to take full advantage of its nitrogen-fixing properties is to cut it down in place after harvest is complete, turn it into the soil and allow it to decompose during the winter months.
How to Harvest Cowpeas
Bounty comes from the cowpea plant in three forms: the edible leaves, the young pods and the mature seeds. The leaves are ready for harvesting three weeks after the seedlings emerge, and you can pick them at any time provided you leave some to allow the plant to keep growing. Young leaves from the top of the plant have the best taste but don't pick the topmost ones at the tip of the stem. Green pods, which you can cook like snow peas or green beans, are ready when they are plump.
When it comes to harvesting the cowpeas themselves, wait until the pods are hard and leathery. Removing the peas from the pod is simple: Just crack open the pod and separate the peas from the fibers to which they are attached. Some may even fall out on their own. If you want to harvest seeds, let the pods dry out completely on the plant before you pick them.
Common Pests and Other Problems for Cowpeas
If any crop is vulnerable to deer, it's cowpeas, so be sure to plant them in an area protected by deer-proof fencing. Rabbits, gophers and other four-legged pests are also interested in the leafy greens and sumptuous roots, so make sure the garden is protected by gopher wire and is rabbit-proofed. If rabbits or deer breach the barriers intended to keep them out, an application of Liquid Fence can help keep them away.
The cowpea plant has more than its share of insect pests, many of which will also be problems for other plants growing alongside them:
- Aphids, which are tiny bugs that gravitate to the undersides of leaves, suck out the juices and deposit sticky honeydew that attracts ants and promotes mold growth. Wash these off with a spray of water or garden-safe insecticidal soap and introduce predators like ladybugs to control them.
- Adult bean beetles look like orange-colored ladybugs, and they have voracious appetites, chewing the leaves from underneath and making large holes in them. Hand pick these beetles off the plants whenever you see them. Use the same strategy if you see Japanese beetles, which are a little larger and have bronze and green coloration.
- Cutworms attack the seedlings and chew them off at ground level. Growers guard against these pests by placing a barrier around the seedlings. A simple barrier can be made by cutting the bottom out of a plastic or paper coffee cup.
- Leafhoppers are greenish insects that jump from leaf to leaf, sucking out the juices and damaging the plants. You can control them with insecticidal soap.
Common Diseases for Cowpeas
- Root rot is caused by a fungus that thrives in moist soil. Avoid overwatering to prevent it, discard any plants that have been affected and avoid planting in the same location. The fungus can live in the soil for up to five years.
- Downy mildew, which leaves gray deposits on the undersides of the leaves, and powdery mildew, which leaves a whitish powder on the tops of the leaves, are both diseases that occur in damp conditions when there isn't enough air circulation. Prevent it by allowing sufficient spacing between plants and watering the base of the plants but not the leaves. You can usually treat it by spraying affected plants with a fungicide. You can also treat powdery mildew with hydrogen peroxide.
- Anthracnose causes large, brown spots on the leaves and turns the seeds yellow and rusty. This fungus lives in the soil, so the best strategy to avoid it is to rotate crops. Do not compost affected plants or turn them into the soil.
Chris Deziel is a contractor, builder and general fix-it pro who has been active in the construction trades for 40 years. He has degrees in science and humanities and years of teaching experience. An avid craftsman and musician, Deziel began writing on home improvement topics in 2010. He worked as an expert consultant with eHow Now and Pro Referral -- a Home Depot site. A DIYer by nature, Deziel regularly shares tips and tricks for a better home and garden at Hunker and Family Handyman.