Nitrogen Fixers
Nitrogen Fixers
This collection includes all the plants we carry that are known to fix nitrogen in the soil. Some of these plants are more efficient than others, some produce a crop too, some are native and some are not native.
What is a 'Nitrogen Fixer'?
In short, nitrogen fixers are sort of like plants that fertilize as they grow, which helps reduce/eliminate the need to add nitrogen to your orchard. Nitrogen inputs (eg. urea) are one of the most common fertilizers used in conventional orchards and can have adverse environmental effects.
Nitrogen fixing plants have a special relationship with bacteria that live in nodules on their roots. This bacteria takes nitrogen floating around in the air, and can transform it into a usable form for plants that is held (or 'fixed') in the soil so the plants can then uptake it. This link further explains the process.
Pictured on the right is a nitrogen fixing nodule on a dormant sea buckthorn plant. In the growing season the nodule will be pink/red in colour when the bacteria living inside is actively fixing nitrogen.
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Species: Gymnocladus dioicus
History: Kentucky Coffeetrees are native to the southernmost parts of Ontario and the midwestern United States. Despite its fairly large range, it is relatively rare today likely due to evolutionary anachronism. It is believed Kentucky Coffeetrees co-evolved with megafauna that are now extinct, so previously beneficial traits like the thick leathery pod around its seeds now hinder seed dispersal. Indigenous peoples have used the tree as a source of food by roasting the seeds and making a coffee-like drink, and the seeds have also been used as pieces in games and to make jewellery. Nowadays, the tree is planted ornamentally in urban areas.
Why We Grow It: This nitrogen-fixing, Carolinian tree produces seeds that may be roasted and used as a coffee substitute, but be aware the raw seeds are toxic! This tree boasts the largest leaves of any native tree, and it's considered a threatened species.
Species: Myrica pensylvanica
History: Northern Bayberry can be found from Ontario to Newfoundland and south to North Carolina, most frequently growing along the west coast. Its berries are a food source for several birds and small mammals. The berries also produce a waxy coating that European colonists used to make candles.
Why We Grow It: This hardy, nitrogen-fixing shrub is a great addition to fencelines, native gardens, and areas that need erosion control. The berries are a good food source for several species and the crafty gardener can also use the berries to make clean-burning candles. They will spread over time.
Available only for pick-up at nursery.
Species: Hippophae rhamnoides
History: Sea buckthorn is native to parts of Europe and Asia where it has been a source of food, medicine, and fodder for centuries. These mystery cuttings were grown by us so it will be a bit of a surprise to see what the mature plants are like!
Why We Grow It: If you're looking for a dense, fruiting bush, look no further! These cold-hardy plants are grown from cutting, although it is uncertain whether each plant is male or female. The nodules on their roots help fix nitrogen into the soil, and the resilient plants are salt tolerant. They can withstand the juglones from walnuts and will reach up to 6 meters tall, forming virtually impermeable thickets if left to their own devices. The berries have a wide range of uses and the leaves can be enjoyed in tea.
Available only for pick-up at nursery.
Species: Caragana arborescens
History: As the name implies, Siberian pea shrubs are native to Siberia but also parts of China, Mongolia, and Kazakhstan. They came to the US with Eurasian immigrants who used the pods as a source of food while traveling. It has been planted ornamentally and as bonsai, and can be used as erosion control. It is also unfortunately invasive in some parts of the US.
Why We Grow It: A classic permaculture plant! Siberian pea shrubs are nitrogen fixing, very hardy, disease and drought resistant, and, above all, edible. The flowers and young pods can be eaten fresh while the older pods are cooked. The plants are also attractive to pollinators.
Available only for pick-up at nursery.
Species: Alnus incana (likely subsp. rugosa)
History: Native to large portions of the Northern Hemisphere including parts of North America, Europe, and Asia, this widespread tree is often divided into six subspecies. We likely offer Alnus incana subsp. rugosa but with seedlings it is hard to say for sure. Indigenous people have used these trees for medicine and dyes, and they can also be used for erosion control. This subspecies in general is unique for its cold hardiness and ability to fix nitrogen, making it a useful companion plant in permaculture settings.
Why We Grow It: Named for the white lenticels that dot the reddish-gray bark, Speckled Alders can make a useful addition to a permaculture with their ability to fix nitrogen. However, keep an eye on this tree as it tends to spread via suckering (sending up new shoots) and layering (branches rooting into the ground) and can form dense thickets.
Species: Hippophae rhamnoides
History: Sea buckthorn is native to parts of Europe and Asia where it has been a source of food, medicine, and fodder for centuries. These seedlings were grown by us so it will be a bit of a surprise to see what the mature plants are like!
Why We Grow It: If you're looking for a dense, fruiting bush, look no further! These cold-hardy plants are grown from seed, and unlike cultivated varieties it is uncertain whether each seedling is male or female. The nodules on their roots help fix nitrogen into the soil, and the resilient plants are salt tolerant. They can withstand the juglones from walnuts and will reach up to 6 meters tall, forming virtually impermeable thickets if left to their own devices. The berries have a wide range of uses and the leaves can be enjoyed in tea.
Species: Caragana arborescens
History: As the name implies, Siberian pea shrubs are native to Siberia but also parts of China, Mongolia, and Kazakhstan. They came to the US with Eurasian immigrants who used the pods as a source of food while traveling. It has been planted ornamentally and as bonsai, and can be used as erosion control. It is also unfortunately invasive in some parts of the US.
Why We Grow It: A classic permaculture plant! Siberian pea shrubs are nitrogen fixing, very hardy, disease and drought resistant, and, above all, edible. The flowers and young pods can be eaten fresh while the older pods are cooked. The plants are also attractive to pollinators.
Species: Shepherdia argentea
History: Silver Buffaloberries are native to the southern parts of the prairies, parts of the northern US with scattered populations further south. It is an important source of food and habitat for many species including Saskatchewan's provincial bird the sharp-trailed grouse. It is traditionally used by indigenous peoples in its range as food, seasoning, medicine, dyes, and in coming-of-age ceremonies for girls.
Why We Grow It: Silver Buffaloberries are an excellent addition to native gardens, food forests, and hedgerows! They are tolerant of a wide array of conditions and are also nitrogen-fixing. These shrubs are some of the first to produce flowers each spring, making them good resource for pollinators. The berries, which are often red but may be orange or yellow, are a good source of food for birds later in the season. The edible berries are on the bitter/tart side but are much more enjoyable when made into jams, jellies, and pies! Just be mindful these shrubs are thorny and will spread over time.
Species: Alnus incana (likely subsp. rugosa)
History: Native to large portions of the Northern Hemisphere including parts of North America, Europe, and Asia, this widespread tree is often divided into six subspecies. We likely offer Alnus incana subsp. rugosa but with seedlings it is hard to say for sure. Indigenous people have used these trees for medicine and dyes, and they can also be used for erosion control. This subspecies in general is unique for its cold hardiness and ability to fix nitrogen, making it a useful companion plant in permaculture settings.
Why We Grow It: Named for the white lenticels that dot the reddish-gray bark, Speckled Alders can make a useful addition to a permaculture with their ability to fix nitrogen. However, keep an eye on this tree as it tends to spread via suckering (sending up new shoots) and layering (branches rooting into the ground) and can form dense thickets.
Species: Gleditsia triacanthos
History: Thanks to its ability to tolerate a host of adverse conditions that would hinder or kill other trees, Honey Locusts have been cultivated for us as ornamental, urban trees. As a result, several thornless varieties have been developed including the mother tree for these seedlings.
Why We Grow It: Honey Locust has many benefits for permaculture and now growers do not need to worry about popping tires with thorns thanks to these thornless trees - though they are seedling so some may develop thorns though most will not; these can be top grafted with a thornless type if needed.. Reaching 30 meters tall, this native nitrogen fixing tree benefits many including bees, wildlife, and even humans: we can use the sweet (honey flavoured) pulp inside their pods in baking, tea or for brewing beer. The durable, rot-resistant wood has a variety of uses.