The Cover Crop Experiment

by Jim Binnings, CCMGA Master Gardener

 

Introduction: Why Cover Crops?

For organic vegetable gardeners, the subject of “cover crops” is being discussed more and more as we stand around the compost bins comparing notes.

 

There has been a lot written lately about carbon sequestering and cover crops. While we all want to do our part and sequester some carbon, I think it is important to point out the primary reason to use cover crops is to improve the quality of your soil so you can grow healthy plants. The jury is still out on whether cover crops make any meaningful contribution in taking carbon out of the atmosphere.

 

In the last few years, my gardening journey has taken me down the mulched path of experimenting more, being more patient with results, and finding more ways to go organic. Here are my first steps in using cover crops to improve my soil.

 

What is a cover crop?

The USDA defines cover crops this way:

“A cover crop is any crop grown to cover the soil and may be incorporated into the soil later for enrichment. Planting cover crops in your garden provides multiple benefits such as controlling erosion, suppressing weeds, reducing soil compaction, increasing moisture and nutrient content of soil, improving yield potential, attracting pollinators, and providing habitat for beneficial insects and wildlife as well as food for animals.”   Cover Crops and Crop Rotation

 

My Goals:

• Keep the soil covered as much as possible.
• Improve macro and micro-nutrient levels in the soil.
• Improve soil structure.
• Attract insects.
• Be aesthetically pleasing.

 

Planning the Cover Crops:

I decided to plant cover crops in my vegetable garden, using sections of the bed that would otherwise go fallow. Late summer 2023, I bought these seeds:

• Oats/pea mix
• Crimson clover
• Vetch
• Fava beans
• Buckwheat
• Soybean
• White clover

 

I also bought inoculant for many of the seeds. My plan was to just jump in and see what would work and what would not. I would observe, keep notes, and learn as I went along.

 

Results to Date

Oat/pea mix. I planted the oat/pea mix in November 2023 and the oats came up immediately. Once the oats started growing, I had to cut them back every month or so to keep them from going to seed. Every time I cut the oats back, I laid the cuttings on the soil which added bio-mass to the vegetable garden and kept the soil covered most of the time. I did not cut the peas back until late spring when they had produced fruit. They both terminated once it got hot in June.

Results: Added biomass, covered soil, improved structure, and added nutrients.
Two Thumbs Up 😊😊

 

Crimson clover. I put the crimson clover seed down in late September 2023 and nothing happened. I had given up on the clover and then in late January 2024 they came up. Within a month or so I had beautiful large clover plants throughout the vegetable garden. By March the clover bloomed and I had crimson colored, flowers throughout the garden. This looked great mixed in with the oats/pea mix, broccoli, and kale. And I started to have bees come by for a snack in spring. By late April/May I terminated the clover. I read that I should not let the flowers bloom too long because the flowers would start using up the nitrogen the clover had just produced.

Results: Added nutrients, covered soil, attracted bees, and looked beautiful.
Two Thumbs Up 😊😊

 

Vetch. I planted vetch with an inoculant in March 2024 and nothing happened. I planted them in an ornamental bed which had been fallow during the winter. I had read that vetch was a great cover crop so I was disappointed. I will try them again. I will put the seed down earlier next time. Probably winter.

Results: No thumbs up yet… But I’ll try again in winter!

 

Fava beans. On a lark, I planted fava beans. I planted them in spring 2024 and they came up immediately. When full grown they were 2ft tall with a single stem. Lots of fruit and I read that the leaves taste similiar to spinach. I terminated them in early summer and laid them on top of soil to cover the soil and left the roots as they were nitrogen fixers. 

Results: Added nutrients, biomass, and were attractive plants.
Thumbs Up 😊

 

Buckwheat. This is the second year I have planted buckwheat. The first year I planted them in late May 2023 and I had good results. In 45 days, I had a lot of blooming buckwheat plants. They attracted a lot of small flies. I waited until the end of July 2024 and had bad results this year. They could not withstand the 100 degree temperatures. A few came up but not many. I terminated them at around two months.

Results: Covered soil, added biomass, attracted insects, and were attractive when blooming.
Thumbs Up 😊

 

Soybean. Again, on a lark I planted soybean. But this time at the community garden. I did not inoculate the seeds and the results were not good at all. However, the plants that did grow produced quit a few seed pods. My idea was to use soybean as a cover crop, harvest them as edamame, and give them to our customers at God’s pantry in Plano. When I called the seed company to find out when to harvest the pods, I was told that if I wanted edamame, I should have planted soybean cultivated to be edamame. Regular soybean does not make good edamame……….who knew!!! So lesson learned……..use the inoculant initially and buy seed cultivated for edamame. Another lesson learned was that rabbits and squirrels love soybean. I would go out to the garden and the soybean would have been eaten. All I had to show for my effort was a plant with a lot of empty pea pods laying around its base. I terminated the plants when the leaves started to turn yellow.

Results: No thumbs up yet. I’ll try inoculating and growing edamame next time!

 

Wood Sorrel. While trying my luck at growing soybean, I noticed a small spreading clover looking plant called wood sorrel growing in the bed. Since the soybean was not doing much, I kept cutting the sorrel back and spreading the cuttings around the bed. By mid- summer the wood sorrel had basically covered the entire bed as a cover crop. The tall pepper plants I had in the bed did fine with the sorrel and enjoyed the company 😊. And when blooming the sorrel had pretty, small yellow flowers which attracted small bees. The sorrel terminated in the hot days of August. Did this surprise cover crop meet my goals? It covered the entire bed with a nice carpet of plants, attracted a lot of small bees, and was very attractive. And I noticed today, September 10th, the sorrel is back and blooming in the partial shade of my pepper plants.

Results: Covered the bed completely, attracted bees, and looked great.
Thumbs Up for the Surprise Sorrel 😊

 

White clover. And lastly, I did not have a chance to plant my white clover but intend to do so this fall.

Results: No thumbs up yet!

 

Lessons Learned

1. Find a seed company that has online and live phone assistance. A catalog is fine, but I had questions since I was growing plants I had no experience with. Most websites have some written guidance. But the company I used had a guy named “Pete” I could talk to about my soybean questions. Pete was very helpful and he saved me time and heartburn.
2. Identify the space you will use for growing cover crops. Like any plant, you will be tying up that space for a season at least. You won’t be able to use the space for other plants. Since I wanted to focus on improving the soil in my vegetable garden I focused on that bed. I also decided that I could clear a small area in the cover crop to dig in a transplant or two (broccoli and kale).
3. Learn when to plant the cover crops. I have learned that the timetable on the seed package is a good starting point but does not always work for north Texas. I am adjusting the planting times for a garden in Texas.
4. Have a general idea about when to terminate the crop. Since I am tying up a garden space for at least a season, I need to know when to terminate the crop to plan for the next crop. The change of seasons seems to be the starting point for deciding when to terminate a crop and plant something else.
5. Be realistic about your expectations. I bought a variety of seeds and am experimenting. Luckily most of the seeds have worked out fine. But I know this experiment could have easily gone the other way with not much to show for my effort. I decided when there are surprises and I just need to go with them. I will try again with the “no show” vetch and embraced the volunteer wood sorrel, which turned out to be a great cover crop.
6. Pay attention and learn what you can about the plant. Since these were new plants for me, I have spent time watching and thinking about them. For example, use inoculant when planting soybean, spread buckwheat seed liberally, put crimson seed down in fall but wait until winter for the show to begin, and cut the oats back regularly to keep them from going to seed too soon.
7. Keep a journal to document how the cover crops are doing. This is big! A lot was going on in my little urban garden and I had a lot of plants to keep up with. If I did not take some time to take some basic notes about what was going on, I would forget and surely make some mistakes over again. You can keep a detailed journal if you want but take basic notes at a minimum.

 

Final Thoughts: Was It Worth It?

Ok, I know the burning question is…. was spending a year learning and growing cover crops in an urban garden worth it? The practical answer is the vegetable bed in my back yard is producing peppers like crazy. This is the best year I have ever had growing peppers. I have four pepper plants that are about four feet tall, and healthy, and I harvest several pounds of peppers every three weeks or so. I am looking forward to peppers now until the end of October. The only man made anything I added was a small amount of bone meal at the beginning when they set their first blooms. I also grew broccoli and kale this spring. Vegetables in Brassicaceae, genus Brassica family of plants have always been a problem for me. Because in the past cabbage white butterflies would find these preferred host plants and lay their eggs all over them. Then the small cabbage white caterpillars would eat the plant leaves until there was nothing left of the plant. This year the broccoli and kale were mixed in with crimson clover, oats, and peas and they did great. I don’t remember having any problems with cabbage whites. I remember seeing a lot of small wasps around the bed earlier than normal. I believe these carnivores had several good meals of small cabbage white caterpillars. Coincidence or did the cover crops bring in the insects earlier than normal? I also remember the bed was so thick with vegetables and cover crops I wondered if all of these different plants confused the insects and they could not find their preferred host plants. Hmmm! I asked but the insects aren’t talking…….haha! I see the benefit of cover crops and that growing them in my vegetable bed reduced having to add man-made stuff. And, I believe my plants were and are healthier for the effort.

 

If you are in a hurry and don’t have time for experimenting… cover crops may not be for you.

If you want exact control and perfection… you might pass on them.

And if you are ok with using man-made fertilizers and amendments...cover crops might be a waste of your time.

If you’re open to experimenting and want to grow organically, cover crops might be just what you need to improve your garden.