Nitrogen Fixers – What They Are and Tips to Get Started

How often have you heard people in gardening circles talk about NPK—nitrogen, phosphorus, and potassium?

If you’ve ever looked at fertilizer from the store, then you will have seen numbers associated with NPK, like 10-10-10.

In the most basic terms, nitrogen helps your plants grow and produce stems and leaves. Plants without enough nitrogen will often be stunted and may even turn yellow.

Because of this, nitrogen is often applied to gardens and farms to encourage plant growth.

But this often results in excess nitrogen being washed into our rivers and lakes, and eventually out into the ocean. This excess nitrogen is causing widespread harm to wildlife, and is endangering public health.

Luckily, there are some excellent ways to work with nature to add nitrogen to your soils, and one of them is very simple.

Plant nitrogen fixers!

Nitrogen fixers are nitrogen-fixing plants that add nitrogen back to the soil through a partnership with special types of bacteria.

Most plants can’t fix their own nitrogen, but a few special groups of plants like legumes (beans, peas, and others) can.

Adding these special groups of plants to your property is a great way to add nitrogen to your soils while limiting the risk of polluting downstream rivers.

I really like mixing in nitrogen fixers throughout my plantings. For example, these plants could be added to your garden in a polyculture planting.

A polyculture is where you grow more than 1 type of plant in a single garden bed.

This could mean multiple rows of vegetables in a single bed, or ideally alternating so no 2 plants of the same type are next to each other. (Corn and some other vegetables are an exception to this rule).

Common nitrogen fixing plants for your garden are your legumes. Vegetables like peas and beans.

Some people also add clovers, which also fix nitrogen, as a groundcover between their rows of vegetables.

But beyond the garden, you can also add nitrogen fixers to your various planting guilds for your food forests, hedgerows, and other perennial growing areas.

Nitrogen fixing plants added to a fruit tree guild will provide a steady supply of nitrogen to your fruit trees and other plants in the guild.

These nitrogen fixers can be non-woody herbaceous plants such as peas, beans and lupines. But there are also a number of great nitrogen-fixing shrubs—some of which are edible!

The key is just to mix in nitrogen fixers throughout your plantings—in your vegetable gardens and food forests and throughout your property.

Each individual plant will only provide a relatively small amount of nitrogen, but all together it will add up and help to keep all your plants growing.

Nitrogen fixers don’t fix nitrogen to be helpful to the plants around them. They fix nitrogen in partnership with special bacteria in order to give themselves a boost.

This is why nitrogen-fixing plants tend to be among the first plants to show up after a big disturbance.

They’re the only plants that can thrive in these disturbed, degraded sites. And I’m sorry to say that for most of us, we are living on land that is badly degraded from human activity—at least when we first move onto them.

Our job is to fix that and cultivate abundance for people, plants and wildlife.

Here in my area, native nitrogen fixer red alder tends to be one of the first trees to grow in disturbed sites.

Over time, these trees improve the soil and help create conditions for the next wave of plants (larger, longer-living trees) to come in and replace them.

This is called ecological succession.

But this natural ecological succession is fairly slow by human standards—so how do we speed it up?

It turns out there is a simple way to speed this process up—all you have to do is chop-and-drop your nitrogen fixing plants on a regular basis.

When you do this, not only do you create a nitrogen-rich mulch on the surface, but you also cause some of the roots of the nitrogen fixers to die off.

As these roots die, some of the nitrogen that is tied up in little nodules (where the nitrogen fixing bacteria are located) will be released.

There is one final way you can mimic nature and use nitrogen fixing plants to cultivate abundance for people, plants and animals.

That is to first plant mostly nitrogen-fixing plants, and then, over time, to replace them with more productive plants.

Let’s look at a food forest to help explain this.

You could plant all fruit trees and then add nitrogen-fixing shrubs and non-woody plants under them.

This works…But depending on your soils, you may want to step back and instead plant 90% nitrogen fixing trees with only 10% fruit trees.

You let those nitrogen fixing trees grow and then you cut them back in mass—say 50% or more of the trees in one season.

This will release a large amount of nitrogen into the soil and also create a lot of woody debris that can be added to the top of your soil as mulch or used to create habitat features to encourage beneficial wildlife.

It will also result in a lot of open spaces—these are fantastic places to plant fruit trees!

The soil in these open spaces will be greatly improved and the woody material will provide mulch in place, which will conserve water and feed beneficial fungi.

All of this will result in the prefect spot for a fruit tree to thrive.

You can continue this cycle until eventually your food forest is 10% nitrogen-fixing trees and 90% productive trees (fruit, nut trees and other trees grown for regular harvests).

What you’re doing is jump-starting the natural ecological succession while still working on nature’s time frame.

This is similar to chop-and-drop mulching, but on a much larger and more intensive scale. But don’t worry if you don’t have space for this sort of intensive method—you can do this on a smaller scale with non-woody nitrogen fixers and nitrogen-fixing shrubs.

The key is to follow the pattern of planting mostly nitrogen fixers on a new site, and then, over time, transitioning it to non-nitrogen fixing plants.

The core takeaway I want you to leave with is this: plant nitrogen fixers!

Far too often, people ignore these plants and instead bring in artificial fertilizers. The result is poor soils, polluted rivers and lakes, and die-offs in the oceans.

By working with nature, we can incorporate nitrogen fixers onto our property and mimic the natural process of ecological succession.

Start by mixing them into your existing plants. This could be as simple as planting red clover around your shrubs and trees.

Then chop-and-drop your nitrogen-fixing plants on a regular basis. Each spring, when the plants are growing but there is still plenty of moisture, go through and cut the nitrogen fixers back.

This will give your other plants a nice boost and also create a fresh mulch layer, which will help your plants deal with any summer droughts.

Then you can take it to the next level. You can start a new planting area by planting mostly nitrogen fixers and then slowly transitioning to more productive plants like fruit and nut trees or other perennial crops.

Using these techniques on your property can let you improve degraded lands and maintain existing productive areas.

Of course, one other method that I didn’t cover in detail is to mix animals—both wildlife and domesticated animals—in your planting areas.

But don’t forget to follow nature’s lead and include nitrogen-fixing plants, too. This is how nature repairs degraded areas and maintains fertility over time, (along with wild animals in the mix).

When you cultivate abundance based on this model, you will have a productive landscape that nourishes people, plants and wildlife without polluting the downstream environment.

What about you? Please leave a comment sharing your favorite way to use nitrogen-fixing plants.