Nitrogen Fixers

Another important aspect of permaculture is knowing what kinds of tools are at your disposal. While there are many different roles plants play in a system, nitrogen fixation is a particularly important one!

Today we will look at a group of plants known as “nitrogen fixers” and how they benefit us.

What is a nitrogen fixer?

A nitrogen fixer is a type of plant that has a mutualistic relationship with a certain type of soil bacteria.

These bacteria live in their roots where they take nitrogen from the air and turn it into a usable form that plants can use.

When this nitrogen is stored in the soil, the plants then provide sugars for the bacteria to live on (you could almost say the bacteria are farming the plants for food!)

These bacteria can actually be observed in the roots of some plants. With many nitrogen fixers you can pull them up and see little lumps (much like small potatoes or peanuts) in the roots called “nodules”. This is where the bacteria live!

Why are nitrogen fixers important?

Nitrogen fixers provide nitrogen for surrounding plants as well as themselves. This is the essential nutrient that allows plants to process proteins, produce chlorophyll, and to provide cell structure among other things.

Practically speaking though this means that it helps plants put on more growth which is especially important for any crops you’re growing for their leaves!

One other important implication of nitrogen fixers is that when used properly they can often eliminate the need for importing artificial nitrogen sources.

This is HUGE in the agriculture space, especially as we think about replacing our modern industrial system with something more sustainable in the long term.

How to Utilize Nitrogen Fixers

Nitrogen fixers can seem like a magical solution (and they kind of are in some ways) however it’s important to know how they actually work.

One often overlooked factor is that nitrogen fixers don’t instantly start producing nitrogen for surrounding plants. It often takes a few weeks just to get the bacteria colonies established in a new spot before they produce enough for the host plant to use.

On top of that, nitrogen fixers often have to be contributing enough organic matter to the surrounding soil in order for it to provide nitrogen to surrounding plants. This means that your plants have to be either dropping leaves or dying back regularly in order for it to have a significant impact on the surrounding soil.

Another factor is what species you decide to use for nitrogen fixation. Not all plants fix nitrogen at the same rate! (If anyone knows of a good database with the nitrogen production rates of different nitrogen fixing species, please send it my way!)

Nitrogen Fixing Plants

This is anything but an exhaustive list, but to give you a starting point, here are some plants that are known to fix nitrogen:

Herbaceous Plants

• Beans

• Peas

• Vetch

• Sweet Pea

• Indigo

• Clover

• Bird’s Foot Trefoil

• Alfalfa

• Cow Peas

• Peanuts

• Lupine

• Licorice

Shrubs

• Goumi (and relatives in the Elaeagnus genus)

• Buffaloberry

• Pigeon Pea

• Sea Buckthorn

• Wax Myrtle

• Wild Lilac

• Bladder Senna

• Bayberry

• Broom

• Cliffrose

Trees

• Acacia

• Alder

• Black Locust

• Kentucky Coffee Tree

• Mimosa

• Wisteria

• Redbud

Obviously this is too many plants to list a couple nurseries for, but I would give a few pieces of advice:

1. Plant what is appropriate in your climate. Not any plant will do well in your area! Use what you have and what does well by you.

2. Don’t overplant nitrogen fixers. You may risk over-fertilizing the soil which can cause other problems!

3. Consider planting edible nitrogen fixers. You can refer to my article on autumn olive for details on where to buy goumi berry if you’d like an edible perennial shrub!

4. Think about natural succession. Many of these plants are pioneer species that may only do well in poor soils, so think of them as pioneer species and how they may be temporary in your journey towards a more productive long-term system rather than a collectible (I’m very guilty of this myself!)

Take a look at my article with some recommended nurseries and seed stores, you’re sure to find plenty of nitrogen fixers!

If you want a more comprehensive list of nitrogen fixing plants, check out this other article by Tyler Ziton of Couchtohomestead

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