Written by David S.
Late Fall, Winter, and early Spring are the times to focus on soil health around your garden and throughout your landscaping beds and containers. Many plants go dormant as soon as the weather turns chilly. However, that does not necessarily mean that the plants are fully asleep. Most plants still have active root systems that are busy expanding in the moist soil and looking for nutrients and water.
As gardeners and landscapers, we should also focus on soil health. This blog addresses nitrogen-binding plants and how they impact winter soil.
What are Nitrogen Binding Plants?
A nitrogen-binding plant has a special relationship with a particular segment of soil biota. They form a symbiotic relationship, and the tiny organisms help change nitrogen trapped in the soil into a usable form of nitrogen that the plant can uptake when its dormancy ends. The plants that have this relationship are also the plants that we call cover crop plants. They include legumes such as peas, clovers, beans, etc.
Now that the heat of summer has passed, we get into winter soil. It is wetter, colder, and often spent. However, winter is an excellent time to focus on rebuilding soil health. Even though the weather is a little colder, the soil in most Southern California locations is more alive than it was during the summer.
The root system uses mainly phosphorous and potassium during the winter. In the spring, when plants begin to leaf out, they need more nitrogen. Winter is an excellent time to focus on helping build nitrogen levels up in the soil. The plants are not using it, but they will need it when it comes to spring, and the plants begin to awake,
An easy way to build nitrogen in the soil is to plant nitrogen-fixing plants. Those include:
- Clovers – Red clover is one of the best clover plants to consider. Its beautiful green leaves and red blooms will also attract pollinators.
- Peas – Sweat peas, snow peas, vetch, and snap peas are all excellent choices. Sweat peas, which will bloom in the spring, are an excellent plant to add to containers. They will perk up the level of nitrogen in the container as they grow. If you have a heavy feeder, such as tomato, plant a few garden peas or sweat peas in the pot with it. They will work to add usable nitrogen to the tomato plant.
- Beans – Fava beans are an excellent choice for beans that grow in winter. Plant fava bean seeds about four inches apart. They will make a fist-sized root ball. As they grow, they will fix nitrogen. In the spring, cut the plants down and turn the plant cuttings into the soil.
The roots are where the nitrogen nodules are and where you will find the most usable nitrogen. That is why we dig the roots into the soil. The root ball will break down, and as it does, it will release nitrogen. The stems and leaves also contain nitrogen, and that is why we dig those into the soil as well. When cutting fava beans, cut them into small pieces so they will decompose faster.
Cover crops are crops that you plant on fallow land. Planting a cover crop in fallow land works because as the cover crop grows, it adds nitrogen to the soil. In winter, you can use peas as a cover crop to revitalize the soil while some other things are growing. Then, in the spring, dig the cover into the ground. We also call cover crops green manure. At the same time, there is no animal byproduct in green manure. It gets its name because it is so rich in nitrogen.
Clover is an excellent plant for cover crops. Clover is in the pea family but does a beautiful job fixing nitrogen in the soil.
Helping Nitrogen-Fixing Plants Thrive
One of the critical ingredients in fixing nitrogen is air. The air we breathe is mostly nitrogen. Aerating the soil allows more air to circulate into the soil, which means nitrogen-fixing organisms have access to more nitrogen. It is the airborne nitrogen that these organisms change.
Aerating the soil is not difficult. There are tools that you can run over the ground, and they will aerate it. We see these used a lot in lawn care. Lawn aerators are available and affordable. You can also use a pitchfork or digging fork to add air to the soil. These are handy tools if there are plants in the area.
If your soil is poor, you can use nitrogen-fixing plants to improve the nutrient load. In addition, it is a good idea to add a bioactive product where the soil is poor. Doing so will help boost soil biota and improve soil health.
Bioactive products contain soil biota, including those that help to fix nitrogen in the soil. For example, suppose you have poor soil considering using both nitrogen fixing plants along with a bioactive product. For nitrogen-fixing plants to do their job, they need soil biota to help convert nitrogen from the air into a form of nitrogen that the plants can use.
Nitrogen-fixing plants are a valuable tool for improving soil health. There are many plants that fix nitrogen in the soil, and most if not all are in the legume family -peas and beans. Thanks to the diversity of these plants, there are enough varieties that you can find one or more that will grow during any season of the year.
It is helpful to use a garden journal to track where and when and what you’ve planted. Also, remember that nitrogen-fixing plants are good options when you take out heavy feeders, such as garden tomatoes. They will help replenish the nitrogen in the soil and may also provide a crop.
Please stop into any of our five Southern California Green Thumb Nursery locations and browse the nitrogen-fixing plants. You can also chat with our garden experts about improving the nutrient levels in your garden or landscaping soil.
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