Nitrogen-Fixing Plants – Improve Your Soil Naturally with These Symbiotic Marvels

You may already know that nitrogen is essential for healthy plants. It's the first number listed in fertilizers, and it's the element that makes leaves deep green and stems sturdy.

Nitrogen is extremely abundant on earth – it actually makes of 78% of the air we breathe. But most plants are at a real disadvantage. Almost all nitrogen exists naturally as a gas, and plants can't "inhale" it.

There are a few plants, however, that love nitrogen gas. These plants pull nitrogen from the sky and store it in their roots in nodules, like the ones you see above. When they die, they leave behind the nitrogen, making that essential soil nutrient accessible for the next plants that grow in that spot.

How Do Plants Fix Nitrogen?

When I said that some plants love nitrogen gas, I lied. They're not the ones that like it – it's actual a common bacterium call Rhizobium that likes it. And the plants like to attract the bacterium. When the seeds of certain plants germinate, they send out a chemical signal into the soil. If these Rhizobia bacteria are present, they "infect" the root hairs of the developing plant. You can even buy Rhizobia on Amazon and add it as an inoculant to your plants.

The bacteria then use the plant to help draw nitrogen from the air. They convert this nitrogen gas and store it in the roots of the plant. When the plant stores the nitrogen in the roots, it produces a lump on the root called a nitrogen nodule. This is harmless to the plant but very beneficial to your garden.

The Most Common Nitrogen Fixing Plants

Legumes

Legumes are the most famous for their nitrogen-fixing abilities. These include all varieties of peas, beans, and peanuts. These are food crops you might just want to grow anyway. Simply plant them in a spot in your garden, then the following season replace them with a different, nitrogen-hungry crop.

Flowers

If you'd rather grow flowers, lupines, false indigo, and sweet pea are all great nitrogen fixers.

Cover Crops

Another classic! Plant cover crops in late summer, then let them die back and decompose naturally over the winter. Popular nitrogen-fixing cover crops include clover, hairy vetch, and alfalfa.

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How Nitrogen Nodules Raise Nitrogen in Soil

While nitrogen fixing plants are growing, they pretty much keep the nitrogen to themselves, locked away in their root nodules. When they die, however, those nodules decompose, and all that stored up nitrogen leeches into the soil. The nitrogen stays in the soil, ready to pass on to the next plants that grow in that spot.

How to Use Nitrogen Fixing Plants in Your Garden

It's a common misconception that nitrogen-fixing plants leak fertilizer into the soil while they are alive. In reality, the plant keeps most of that nitrogen for itself. It's only after it's died that it gives back to the community.

To get the maximum amount of nitrogen into your soil, try the Chop and Drop method.

1. Wait until the plant has just started to flower – this is when nitrogen levels are at their peak.
2. Cut the plant at the soil line. Leave the vegetation where it falls – it'll act as a nitrogen-rich mulch.
3. Don't pull the roots out! Leave them to die underground and rot. As they decompose, those nodules burst, releasing a slow-motion "nitrogen bomb" directly into the root zone of your next crop.

If All Else Fails...