Nitrogen fixing plants are a very special type of plant that lives in symbiosis with nitrogen fixing bacteria. The plants form nodules on their roots and release nitrogen in to the soil.
With many of these plants, they only release the nitrogen when the roots die, so it is good to have some of these plants that you chop and drop before they form seeds – plants will send the nitrogen up to the seeds which is why animals like chickens that eat large volumes of seeds have high nitrogen poop!
Benefits of increasing nitrogen in the soil
The benefits of having more nitrogen rich organic matter in the soil include:
- higher general productivity, especially in fruiting plants
- richer and more diverse soil life
- more available phosphorus
- higher availability of various other nutrients
- higher capacity to hold nutrients
What type of plants fix nitrogen?
Generally speaking, legumes are what you are after if you want to fix nitrogen in to the soil. There are other nitrogen fixing plants, but not all of other families of other plants are nitrogen fixers. So if in doubt, plant a legume! Otherwise there is quite a substantial list of nitrogen fixing plants below.
What are the best nitrogen fixing plants?
The most commonly used nitrogen fixers are clover, beans, peas and lupins. This is because they are easy to obtain, the grow fast and tolerate most climates and they make great chop and drop mulch in a food forest garden setting.
There are however, many many other plants that fix nitrogen in the soil. These range from cover crops, to herbs, to flowers to whole trees!
The best Nitrogen Fixing Plants to grow in your Permaculture Garden or Food Forest
Here are the best nitrogen fixing plants for your garden or food forest, they are split in to plant types, then listed alphabetically.
Nitrogen fixing trees
California mountain mahogany
Chinese Yellow Wood
Golden chain tree
Inga tree (tropical)
Kentucky Coffee Bean
New Jersey Tea
Persian silk tree
Purple Coral Pea Shrub
Siberian Pea Shrub
Silverberry (Elaeagnus x ebbingei)
Nitrogen fixing cover crops / green manures
Lespedeza, Serciea (perennial)
Peanut, Perennial (perennial)
Nitrogen fixing flowers
Indigo (all Indigofera genus)
Purple Coral Pea Shrub
Nitrogen fixing edible food plants / vegetables
Beans, All Others (black, anasazi, lima, kidney, etc.)
Breadroot (Prairie Turnip)
Nitrogen fixing herbs
Nitrogen fixing vines
Bean, Scarlet Runner
Bean, Wild Groundnut
Kudzu (Japanese arrowroot)
Peas, Vining Garden Peas