Written by Andy Behlen, Fayette County Record
I love fresh peas from the garden. I’m amazed at how nature found a way to turn soil and sunlight into something green and sweet. I love the way they look growing up a trellis. They can provide a beautiful architectural element to the garden space.
I grew a variety called “Oregon Sugar Pod II” this year. This is a variety of snow peas. You can wait to pick them until the pods fill with plump peas. However, most folks who grow snow peas pick them when the pods are slightly immature. You can eat the entire pod this way.
I planted these peas in a row back in late January. The seed package said they would reach maturity in 68 days after germination, and that was pretty accurate. I picked the first harvest about a week ago, and the vines are already loaded with peas again this week.
The more you pick them, the more they produce. This is a trait common to most of the legumes grown as vegetables, which include green beans, lima beans, black-eyed peas along with English peas, sugar snap peas and the snow peas I’m growing.
Gardeners get an extra benefit from growing legumes in addition to the harvest: they have the ability to transfer nitrogen from the atmosphere into the soil. This process is called nitrogen fixation. Nitrogen is one of the most important nutrients for plant growth.
A few weeks ago I spoke with Fayette County AgriLife Extension Agent Scott Willey about this topic. He made an important point – legumes need nitrogen to grow just like any other plant. If you plant them in poor nutrient-deficient soil, they’ll struggle to grow. They’ll never reach their genetic potential, and they probably won’t fix much nitrogen in the soil. So you need to fertilize your peas and beans just like any other plant in the garden.
The benefit from nitrogen fixation comes later, after the legumes are done producing for the season. But first, let’s take a look at how this process works.
Approximately 78 percent of the air we breathe is nitrogen. But it’s not in a form that plants can use. Legumes have developed a symbiotic relationship with a family of bacteria called Rhizobium. Some species of Rhizobium are specific to certain species of legumes. Most soils contain Rhizobium, but it might not be the species specific to the legume you’re trying to grow. Thankfully, many garden centers sell legume inoculant that contain the right species of Rhizobium for various legumes. It’s a good idea to inoculate legume seeds, especially if you are planting them in a spot for the first time. Just follow the directions on the package. If you plant the same legume species in your garden over the course of a few years, Rhizobium will build up in the soil and you may not need to inoculate every year.
Rhizobium bacteria live in tumor-like structures called nodules that are attached to legume roots. An article from Texas A&M Agrilife explains the process: “These bacteria can take nitrogen gas from the air in the soil and transform it into ammonia (NH3) that converts to ammonium (NH4) which can be used by the plant.”
Many row crop farmers know about ammonium nitrate and ammonium sulfate fertilizers. These fertilizers are very similar to the ammonium produced by legumes.
Legumes do not release much if any nitrogen produced through the fixation process into the soil. Instead, the nitrogen gets stored in the plant’s roots, stems and leaves. After the growing season, when the plant dies, the plant decomposes and becomes part of the soil. For the gardener, this is the primary way in which “fixed” nitrogen gets transferred from legumes into the soil.
At the end of the growing season, don’t pull up your peas or beans and throw them away. Instead, chop them up and incorporate them into the soil. A lawn mower makes quick work of this. Planting legumes as part of a soil improvement program works great for no-till growers like myself. Instead of pulling the plants – roots and all – at the end of the growing season, I simply mow the tops and leave the roots in the ground. This provides a little nitrogen for the next crop I grow in that spot. I also practice crop rotation so that every spot in my garden grows some legumes from time to time.
It’s probably too late in the year to plant green peas (Pisum sativum), but you can still plant green beans (Phaseolus vulgaris). Cow peas and blackeyed peas (Vigna unguiculata) are another species of legume that loves to grow in our climate, especially during the heat of the summer when most other beans play out. Some of my favorite varieties are the Asian cultivars known as yard-long beans. They are the same species as cow peas and blackeyed peas, but the pods grow up to several feet long. Instead of shelling them like cow peas or blackeyed peas, the pods stay tender enough to eat whole.
Andy Behlen is a reporter and digital editor for The Fayette County Record Newspaper in La Grange, Texas. He writes a weekly column focused on organic gardening. Reach him at firstname.lastname@example.org
Welcome to the discussion.
Keep it Clean. Please avoid obscene, vulgar, lewd, racist or sexually-oriented language.
PLEASE TURN OFF YOUR CAPS LOCK.
Don't Threaten. Threats of harming another person will not be tolerated.
Be Truthful. Don't knowingly lie about anyone or anything.
Be Nice. No racism, sexism or any sort of -ism that is degrading to another person.
Be Proactive. Use the 'Report' link on each comment to let us know of abusive posts.
Share with Us. We'd love to hear eyewitness accounts, the history behind an article.