Native Plants that are Impressive Nitrogen-fixers
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Nitrogen-fixing plants are those that form a symbiotic relationship with Rhizobium bacteria (which reside in their root nodules), allowing the plants to convert nitrogen from the atmosphere into usable forms to enrich the soil and support plant growth. Some plants can also accumulate nitrogen, but appear to do so without the help of Rhizobium bacteria.
One native, perennial legume with nitrogen-fixing properties is wild thicket bean (Phaseolus polystachios). This remarkable, perennial vine additionally accumulates phosphorus (P), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg), silica (Si), iron (Fe), boron (B), copper (Cu), manganese (Mn), and molybdenum (Mo). The cooked beans are also edible, but as with most legumes, while some minerals do accumulate in various parts of these plants (like Ca and Fe in the leaves), the highest numbers of minerals tend to accumulate in the beans, so if all the beans are harvested for consumption, less of the accumulated nutrients will remain to benefit the soil and surrounding plants.
Similarly, hog-peanut (Amphicarpa bracteata) is a native accumulator of nitrogen (N), along with K, some P, Ca, Fe, Cu and Mn. In this case, these minerals are in her shoots. The light brown seeds from her underground pods are reportedly edible after boiling for several minutes.
Another native plant that accumulates N as well as K, Fe and Mn in the roots is perennial milk vetch (Astragalus canadensis). If desired, the roots can also be used to make a restorative tea.
A native berry bush that accumulates nitrogen is buffaloberry (Shepherdia canadensis). If you wish, the berries can be made into jam or jelly.
There are many additional, native plants that fix or accumulate nitrogen, including:
- groundnut (Apios americana), a perennial, twining vine with edible tubers
- northern bayberry (Morella pensylvanica), a perennial shrub that additionally offers therapeutic benefits
- American wisteria (Wisteria frutescans), a perennial, woody vine (some roast the seeds as a coffee substitute and make fritters from the flowers)
- wild indigos (blue: Baptisia australis, and white: Baptisia alba), perennials with therapeutic properties
- false indigo (Amorpha fruticosa), a perennial shrub
- black locust (Robinia pseudoacacia), a deciduous tree
- partridge pea (Chamaecrista fasiculata), an annual plant
- prairie clovers (purple: (Dalea purpurea), a perennial, and foxtail: (Dalea leporina), an annual)
- vetches (American: Vicia americana & Carolina: Vicia caroliniana), both perennial plants
These represent just a few of the many native plants that can bring beneficial nitrogen to your cultivated areas. And while nitrogen-fixing plants can indeed offer benefits, it is important to select plants that are most suitable to your situation and environment. Combining them with additional, natural methods can help further improve the ecologic health of your area.