Guest Blog by Matt Suhr of Happy Dirt Veggie Patch

Peas come in pods and are members of the legume family. The legume family is special because these plants form symbiotic relationships with nitrogen-fixing bacteria in little nodules on their roots. But before we expound upon peas, let’s review some science:

The Science of Peas

Nitrogen, N, is essential for all plants because it is a building block of all proteins. In order to get the N they need, most plants take what is available in the soil from the breaking down of proteins from dead organisms, or waste excretions from living organisms. This works well when there is an abundant supply at hand, but N found in the soil is easily depleted and returns to gaseous form in the atmosphere. While abundant in the atmosphere, nitrogen in this form, N2, is not chemically available to plants directly, because it is tightly bound to itself.

Plants can literally starve for N while immersed in an atmosphere that is 78% N2.

nitrogen nodules on pea plant — Nitrogen Nodules on the roots

Enter legumes, and a family of bacteria called rhizobia. There are a few other plant genera and bacteria combinations that can sequester N from the atmosphere, but legumes with rhizobia are the champs. They have figured out how to crack the code with enzymes that split the N2 and allow it to form compounds such as ammonia, urea, nitrates, amino acids and ultimately proteins.

These symbiotic relationships are the primary way N is introduced into the soil biome. The only other pathway is through lightning, which can also split the tightly bound N2 molecules, but adds only about 1-2% of the total soil N worldwide. The rest is from soil bacteria. The bacteria gather in protected nodules along the roots, which trade N to the plant in exchange for carbohydrates that the leaves produce, and it’s a win-win.

All of this is to say that peas are a great crop to grow, for more than their direct food value.

As legumes, peas are soil builders. They leave significant N behind in the soil that greatly benefits subsequent crops. For many crops, and in many soils, N is the limiting nutrient that determines growth rate. While there are synthetic fertilizers that can supply N, using these products will disrupt the delicate N cycle balance of the soil biome, possibly leading to dependence on the fertilizer, weak insect-prone rapid growth, weakened roots, and runoff pollution due to excess N, among other problems. In a garden setting it is very difficult to regulate the optimal release of N to plants from synthetic fertilizer. It is generally better to rely on the natural soil processes using natural N sources–slow and steady.

Okay, now that the science lesson is out of the way, let’s get into peas!

Pea Varieties

There are many varieties of peas. For the purpose of this article, we’ll mention five general categories:

English Peas

These are the classic shucking peas that Grandma grew. Also known as garden peas. Tasty little green balls in pods that are tough and inedible. It seems like a lot of work to zip open a pod and get maybe 8 or 10 peas, so these have become less popular as a garden crop. Or maybe everybody just got lazy. The flavor of freshly shucked peas is outstanding! And the plants yield heavily, so this is actually a good deal of protein for the effort.
Commercially, English peas are still a big item keeping the world abundant in frozen and canned peas.

Snow Peas

These are native to SW Asia, and first became widely cultivated in China. They are picked when the pod is still immature and flat, with only minimal development of the individual peas inside. The entire pod is edible, though sometimes accompanied by tough strings that need to be zipped off. Their flatness makes them ideal for cooking in stir fries, as they cook quickly and evenly, and provide great pea flavor without the need for shucking.

Snap Peas

There are references in French literature to plump edible-podded peas called “butter peas” going back as far as 1670. These were lost to cultivation by the 20th century, and no plump edible podded peas were available commercially until 1979. That is when “Sugar Snap”, bred by Calvin Lamborn, was introduced. He crossed a snow pea with a mutant thick-podded English pea. It was an instant sensation, and is now many people’s favorite pea, coming in many named varieties. The entire pod with plump peas is edible, though often there is a fibrous string that needs to be removed.

Field Peas

Also known as cowpeas, black-eyed peas, Southern peas or crowders. This category also includes many varieties grown primarily as cover crops. Technically they are more of a bean than a pea.

Sweet Peas

These are grown for their beautiful and aromatic flowers. They are legumes, but not true peas. They are not edible, and if large amounts are consumed can be quite toxic.

Variety Selection

The criteria for selecting which variety of pea to grow comes down to three things:

What are the culinary or growing characteristics that are desired
Whether it is a bush type or climbing vine
What disease resistance does the variety have

Thumbing or scrolling through a catalog, you will see many options. Whether you want something unusual or specific, or a common variety, the growing needs for most all peas are quite similar. If you don’t know for sure what you want, the more common varieties that show up repeatedly in catalogs are your best bet for something widely adaptable and likely to succeed.

In choosing a variety for disease resistance, you need to know beforehand what diseases are common in your area, and see if you can find a variety with built-in resistance. In dry regions diseases tend to be less of a problem. With good cultural practices and some luck your crop will make it through the season disease-free. Some diseases like powdery mildew tend to come toward the end of harvest time when the plants are tired and almost done, so you can live with it to a degree. See Pests and Diseases below.

Timing

Peas in general prefer cool conditions to thrive. The exception is field peas, which thrive in hot summer weather.

Planting time depends on your climate. In mild-winter climates late fall (Nov/Dec) is typically the best time to plant cool loving types, and early spring (March/April) for field peas.

For other areas, cool loving types can go in “as early as the soil can be worked”. That translates into a month or two before the average last frost date. There is not much worry about planting too early, as they will germinate very slowly if it is too cold. The young seedlings are quite hardy down to the low 20’s F. The planting window lasts until about the average last frost date. If planted too late, they will yield smaller, lower quality crops due to heat. Ideally peas will mature when the weather is just getting warm but not yet hot. This is also typically when hay fever sneezing season hits it peak.

Field peas in cold winter climates are best planted when the soil temperature hits around 60-65° F. That is somewhere in April or May at most locations.

There is another narrow window for planting cool-loving peas in mid-summer. If your climate is not extremely hot, peas will germinate in mid-summer, and will grow begrudgingly in the heat as young seedlings. By the time they are ready to flower and make peas, the weather will have cooled enough to allow the plants to begin to flourish and yield a nice crop of peas just as fall sets in. The danger with this method is that if you plant too early the heat will still be too much as the flowers and pods are developing. If you plant too late, the pods risk being damaged by frost.

Although young pea plants are frost hardy, the flowers and pods on mature plants are not. So with mid-summer planting you need to find the perfect timing for your area, typically about 2 ½ months before frost, or somewhere around mid to late July. These late crops are very nice and unexpected, but overall yields tend to be less than with the early crops. Choose varieties that are early and resistant to powdery mildew.

Soil Prep

While peas are pretty good at supplying their own nitrogen, they prefer otherwise fertile soil to yield abundantly. Phosphorus, P, is the key nutrient. Other minerals are needed in modest amounts. Bone meal, aged compost or manure, earthworm castings and seabird guano are good sources for P. Rock based phosphate fertilizer takes a very long time to break down and become available. Synthetic superphosphate fertilizer works, but risks a toxic build-up in the soil which then leaches with heavy rains or irrigation to pollute waterways– potentially causing eutrophication (algae and aquatic plant overgrowth, leading to oxygen depletion and fish kills).

Peas are adaptable to many soil types, but do not tolerate poor drainage. If there are persistent puddles after a rain, peas will have difficulty thriving. If excess moisture is a problem in your garden, the best bet is to use raised beds to keep the pea roots out of the saturated zone as much as possible.

Peas need full or almost full sun to yield well. They do not require extensive soil prep. Decide what amendments you will add, sprinkle them on the surface, take a digging fork or narrow trench shovel and lift sections of soil to form cracks that let the magic goodies drop down. If it is hard to get a digging fork or shovel into the soil, then soak it deeply with water and come back in a day or two. Compacted soil will inhibit root growth. Most often, soil is compacted only in the top 8-10 inches. Once you can get your tool deep into the soil and lever it up like an earthquake you are good to go. No need to thoroughly turn it or mix it all up. Just crack it through the compaction zone and the roots will find their way and finish the job.

Planting

Pea seeds can be given a little head start by soaking them overnight or until they swell up. They will hold like this for a few days as long as they don’t dry out again. Soaking is optional, and is particularly helpful if you are planting in dry conditions. In moist conditions they do fine planted without soaking.

When you are ready to plant your peas, make a furrow with a hoe about 2 inches deep…

But before you plant, you probably will want to inoculate your seeds. Remember the discussion about rhizobia? The nitrogen-fixing bacteria live naturally in many soils, but typically in small numbers. Once they encounter legume roots they will begin to multiply and form the nodules that feed the N to the plant. However, this process takes awhile to get going. During this period the pea plant will be short of N and grow slower than its potential. There is a way to jump start this process and ensure that the right species of rhizobia is easily accessible to the roots: inoculate the seed with the proper species. It’s easy. Get a container such as a jar or old plastic cup big enough to easily hold the amount of seed you intend to plant with plenty of room to spare. Put in the dry seed and then add a tiny, tiny amount of water. Literally just a few drops! Then add the inoculant powder at the recommended rate. It is usually a black powder that adheres quickly to the moist seeds. Swish it around until all the seeds have a good amount of powder stuck on them.

Inoculants are readily available from most seed catalogs and many local nurseries. It usually comes in a small plastic pouch with enough for several pounds of seed. It is important to use the correct species for your type of pea. The English, snow and snap varieties all use the same species which is commonly included in the pouches labeled “garden combination”. Field peas and sweet peas have their own species that they associate with, and are available separately.

If you do not inoculate, you run the risk of a disappointing crop. Or it may do just fine. It depends on what is in your soil to begin with. Most growers find that it is cheap and easy insurance to inoculate. There is no risk of overinoculating.

Now it is time to plant. After inoculating, get your seeds in the ground right away. Once moistened, the bacteria activate and become sensitive to sunlight and drying out.

The seeds can be planted about 1 inch deep in heavy soils or wet conditions, and 2 inches deep in sandy soil or dry climates. You can pull an upside down bow rake over your furrow carefully and control how deeply the seeds are covered.

Unlike most garden crops, peas (except for field peas) can be planted close together without the need for thinning. There are limits to crowding, of course, but in general peas will manage well over a wide range of spacing. Ideal is anywhere from 1 to 4 inches apart in a row. Planting in straight rows rather than broadcasting or grid patterns is recommended if you are going to trellis your peas (see support below).

If you are planting field peas as a cover crop, use 3 inch spacing or more in the row and allow 24-30 inches between rows. Crowding field peas causes spindly rather than bushy plants, and wastes seed.

You can extend your season if you plant succession crops of peas. This works best with winter/spring plantings. The summer planting window is too narrow. Planting some peas every 2-3 weeks until the last frost date will give you a maximum span of harvesting.

Growing On

Peas can take anywhere from a week to a month or more to germinate. Warm temperatures make them sprout quickly, cold slows them down. In early spring conditions, two to three weeks is common.

When they first pop out of the ground, peas are very attractive to birds. They are often the only bright green growing thing around at the time, and your row of peas could disappear shortly after emerging unless you cover it with row cover fabric or the like. They are vulnerable to birds until they get about 3 inches tall. Sometimes birds will nip the edges of the leaves only, but too often they yank the whole thing out of the ground or nip it off at the base.

Once they have survived the birds, peas are pretty resilient–except for wind and gravity. Pea plants are structurally weak and once they get crimped over from wind, or getting knocked over by you or a critter, they are slow to recover. So keeping them upright and stems uncrinkled is important.

Support

Bush varieties mature a bit earlier, but overall yield is less than the vining types. They are much more popular for commercial production as they don’t require trellising. Even so, they will still benefit from having some kind of support. Single rows that are unsupported tend to flop over in the wind. If you plant two rows of bush type about a foot apart, they will reach and cling to each other and form a thicker, more wind-stable hedge than a single row would.

One simple way to support bush peas is to use some old dead brush, with bark and small twigs still attached, and press it into the soil in the row. This gives a skeleton structure of sorts for the peas to cling to and keep the pods off the ground.

Vining types require a sturdy support that allows the tendrils to wrap around and hold the plant up. The tendrils can only grab onto materials less than about ½ inch in diameter. Wire or twine are the materials of choice. The height of the plant can range anywhere up to 8 feet, depending on variety, though 5-6 feet is more typical. Your support must be tall enough and strong enough to hold up the plants, even in a strong wind. If using wire fencing or string mesh supported on a rigid frame, it really helps if the openings are big enough to easily reach your hand through. Come harvest time you will appreciate this a lot.

When they get to around 8 inches tall and you see some tendrils forming your plants are ready to start climbing a trellis. Place the trellis directly above or adjacent to the plants so they can find it. Once they find and attach to the trellis, the plants will grow quickly and fill the space with foliage. It is good to mulch around the base of the plants during this phase to keep the soil temperature cool and discourage weeds.

Pests and Diseases

Peas are prone to a wide range of pests and diseases, especially in humid climates.

Common pests include aphids, pea weevils, nematodes, various beetles and caterpillars.

Aphids– these are little suckers in colonies on the undersides of the leaves. They can spread diseases, but in small numbers can usually be tolerated. If they become a full on infestation, Safer® soap or neem oil sprayed on will usually take care of it. Spray only during cooler morning and evening hours to prevent burning of the leaves.

Pea Weevils– these first show up as tiny (<1mm) yellow cigar shaped eggs randomly stuck onto the pods. They can be easily washed off, so no big deal as far as eating the fresh peas. However, if you are saving seed or growing dry field peas, these bugs will bore big holes through the peas and make them pretty useless. Their life cycle makes control with sprays nearly impossible. Best is to avoid letting damaged peas fall to the ground. Thorough early harvest and removal of damaged peas is the most practical way to prevent future infestations.

Nematodes– these are microscopic worms that infest the roots and can cause problems like yellowing leaves, stunted growth or small leaves. There is not much to be done to save plants from nematode damage. If they are a problem, you can solarize your soil with clear plastic in the hottest time of summer to get rid of them. Crop rotation is also recommended. Planting cover crops can also help limit their numbers.

Beetles and Caterpillars– anything that is chewing the leaves of your peas can be dealt with in one of three ways:

you can hand pick them off ;
you can spray with any of various products that contain Bt, which is a natural bacteria that kills the larval stage of just about any leaf-munching insect; or
you can spray with a thick slurry of diatomaceous earth and let it dry on the leaves.

Common diseases include pea root rot, powdery mildew, downy mildew, Fusarium wilt and root rot, pea leaf roll virus, pea enation virus, and bean yellow mosaic virus.

These diseases are difficult to impossible to eradicate once they gain a foothold, so prevention is the way to go. The easiest prevention is to plant varieties that are resistant to whatever disease is troublesome in your garden. Most quality seed catalogs will list the various resistances with abbreviation codes.

The other general approach is to be sure to provide the basic conditions that peas love:

well-drained soil,
good air circulation but not blasted constantly by wind,
full sun,
cool weather,
mulch,
balanced soil fertility.

Avoid overhead watering. Drip or flood irrigation will keep the leaves dry. Mulching will help prevent rain splash from getting soil pathogens on the leaves.

Some of the viruses spread through sucking insects like aphids. It is very difficult to prevent occasional insects from sucking on your plants. In gardens, it is most common for viruses to attack only a small number of plants. In those cases, it is best just to live with it. If your entire crop is getting wiped out, planting resistant varieties is the way to go.

Harvest

When you start to see blossoms forming, harvest time is near. Hopefully at this time the weather is mild and settled. Hot weather can cause blossoms to wither and the pods to become mostly devoid of peas and no longer tasty. If heat hits unexpectedly early, your best bet is to mulch heavily and at least keep the roots cool.

Harvesting each pod at the right time is important. Picking too early or too late will drastically reduce quality. Picking every 2 to 3 days will make it easy to get them all at the right stage.

Here is what to look for:

English peas- plump pods that are still bright green, peas inside are full size and bright green
Snow peas- pods are flat and bright green with tiny lumps of immature peas.
Snap peas- pods are plump, bright green, with a more cylindrical– not oval–cross section. Peas are almost fully formed but not yet starchy. (If you miss some and they turn starchy, they are still delicious when cooked!)
Sweet peas- these are grown for their flowers. If saving seed, pick the pods when they turn yellow/brown and feel dry, but before they pop open on their own. Put in a well ventilated container to finish drying.
Field peas- for fresh use, harvest when pods are green and seeds are soft. For dried beans, harvest when the pods are brown and dry, before any rainy spell. Lay them out on a tarp in a dry place to finish drying.

Being fragile plants, you want to pick peas gently with as little stress as possible to the plant, so they will continue producing as long as possible. This means using two hands, or doing a pinch maneuver with thumb and index finger to pop off a pod. The main thing is to not “yank” them.

Keep the plants picked! If you let too many pods get away from you and develop into seeds the plant will have satisfied its reproductive urge and will stop producing new flowers and pods. This is particularly true for tall trellised peas. Bush types have a shorter harvest period by design.

To save seed, just let some of the nicer looking pods keep developing until they are tan color and the peas inside are hard. Be sure the seeds are totally dry before storage! Peas are self-pollinating, so the seed you save will almost certainly perform the same as the original crop.

After harvest is done, your peas will still be adding value to your garden by virtue of the nodules on their roots. Remember rhizobia? The nitrogen that these bacteria have gathered to supply the plant is released slowly back into the soil for the next crops to utilize. Peas leave the soil more fertile than they found it. You can remove the dead plants from the surface and leave the root system intact. The old roots will decay away leaving N free for the taking. The plant tops are a great addition to the compost pile, or can be mowed to make some mulch.

Whew! You did it! You supplied yourself with tasty, high protein, nutrient-dense peas and improved your soil in the process!

Matt has grown vegetable gardens in New Jersey, Illinois, Utah, Arizona and Oregon. His adventures in the business of agriculture began in 1986 with wildcrafting seeds of numerous native plant species in the desert Southwest for seed companies. This transitioned to establishing several community gardens and small market farms including The Farm at South Mountain in Phoenix, AZ; Native Seeds/SEARCH conservation farm in Patagonia, AZ; as well as his own HappyDirt Veggie Patch in Tempe, AZ and several other locations—moving to Ashland, OR in 2008. Happydirt has recently moved to Myrtle Point, OR.

Growing Peas, Growing Soil