Nitrogen Fixers for Permaculture

Honey Locust

Honey locust is so named because of the color of its wood. The blossoms are not a good nectar source. The usual “honey locust” has huge multi-branched thorns. Beware! The “honey” in the name refers to the color of the wood. Thornfree cultivars are available, but will be more expensive.

 seeds trees buy tree seeds
 seed for sale online




Thornless Honey Locust Gleditsia triacanthos Inermis
1 lb for $24.50 Seeds Per Pound: 2,270

Locust tree descriptions at Willis Orchards

Honeylocust (Gleditsia triacanthos)
Reasonably priced.

HoneylocustThis hardy fast growing ornamental plant does not actually produce honey. The seed pods do, however, have a honey-like sweet taste. Many mammals, especially deer, have been known to stop and pluck the flavorsome pods right out of the tree. The sugary pods, which contain the honey locust seed, are extremely high in protein. Often honey locust is planted near the edge of a food plot or pasture to supplement the diet of large grazing mammals such as deer and cattle.

The flowers bloom in late spring, followed by seed production between September and October.  As January rolls around and the cold of winter approaches, the honey locust tree still provides food for game. We have also seen white tail deer as well as rabbits routinely chomp the bark of this sweet tasting tree. When planting this remarkable tree, remember that they prefer to live mostly in the sun. So pick a spot on the edge of a field or along a stream and your new honey locust should be providing food in no time.  Keep in mind that Southern soils produce sweet pods, while the pods tend to be less attractive in northern soils.

Zone: 3 – 8
Soil pH: 6.0 – 8.0
Mature Height: 75′
Wildlife Value: Pods eaten by deer, possum, squirrel, rabbit, and quail. Bark eaten by deer and rabbit.
Site Preference: Mountain slopes, moist bottomlands, along streams, limestone prairie soils.
Fruit Maturity Date: Early Fall
Alias: Beantree

Black Locust

The black locust tree is a reliable nitrogen fixture recognized by permaculturists. It is also a source of nectar for bees, but its pods are not generally considered edible.  It has small sharp thorns at the base of new leaves, but thornless varieties are available.


Another thorny nitrogen fixer:
Leguminosae (Fabaceae)
Mesquite is one of the most widely distributed trees in Texas. It is a small to medium tree with an irregular crown of finely divided bipinnately compound foliage that casts very light dappled shade underneath. It is armed with thorns sometimes up to 2 inches long. In the spring, summer and after rains it is covered with fragrant white flowers, and the long bean pods are ornamental as well as providing food for wildlife and livestock. Mesquite is not a rancher’s favorite tree: it readily invades overgrazed sites and other disturbed land, is virtually impossible to get rid of, and the thorns injure livestock. However, the foliage, flowers and fruit are attractive, it adapts to almost any soil that is not soggy, it is heat and drought tolerant, it fixes nitrogen in the soil and provides many areas of Texas with shade, fuel and timber where otherwise there would be none. The wood is used in flooring, furniture, and as a cookwood for seasoning.

Thornless varieties??

Eleagnus Genus

known by the common names thorny olive,[1] spiny oleaster[2] and silverthorn; also by the family name “oleaster”. It is native to Asia, including China and Japan.

How to root eleagnus

The Eleagnus genus (Autumn Olive, Goumi, Silverberry, Treboizond Date) consists of shrubs and trees that produce fruits with remarkable qualities. They are high in vitamin A and E, bioactive compounds, minerals, flavinoids and proteins. Their lycopene content is the highest of any food and is being used in the prevention of heart disease and cancers and in the treatment of cancer. Cooking the fruit increases the lycopene content. The fruits and seeds are a good source of essential fatty acids as well which is very unsual for a fruit. The seeds are also edible although somewhat fiberous, and are especially high in proteins and fats. All of the eleagnus species are nitrogen fixers. They take nitrogen out of the air and put it into the ground through a symbiotic relationship with a bacteria that lives in their roots, thereby improving the fertility of the surrounding soils. The shrub species of eleagnus are sun or shade tolerant and can be interplanted with larger nut trees to their benefit. Autumn Olive was so widely planted on mine reclaimation sites in the mid 20th century that it has extensively naturalized in some regions. In some Eastern and midwestern states Autumn Olive has acquired a reputation of being a potentially invasive plant. We’ve grown Autumn Olive for 30 years and in all that time have observed two volunteer plants. In the mid 20th century millions were planted on mine reclamation sites since it is able to “fix” nitrogen out of the air and put in the soil, improving the quality of the soils much like clover does. Since the plant produces masses of fruit that birds love to eat it doesn’t surprise me that its spread out beyond where it was planted. Birds do tend to fly around about and the seed then gets widely dispersed. Autumn Olive is very widely adapted and will grow in the sun or shade. We planted it as an understory in out walnut orchard as walnuts are heavy nitrogen users so they grow faster with an understory of Autumn Olive. It is a shrub so its spread could be controlled by netting it with bird netting just before the fruit ripens in September, since birds are the primary agent of seed dispersal. That way you can enjoy all the fruit and not have to worry about it spreading. Young seedlings of eleagnus can be fairly thorny, very useful for a hedgerow. Older, mature plants and named varieties grown from cuttings have few if any thorns.

Goumi/Gumi Berry/ Cherry Elaeagnus

Just Fruits Goumi – Eleagnus multiflora

goumi-just-fruits(Fruit astringent, sweet-tart) This fast-growing shrub has many excellent qualities aside from its small red fruit called goumi. Light, lilac-scented flowers appear in April or May, developing into small fruit that can be eaten raw or cooked. The fruit is astringent until ripe, but can be made into pies and jams if picked a little early. Goumi are a rich source of vitamins A, C and E and are under investigation as anti-cancer agents. The deciduous bush can grow in almost any well-drained soil (including by the seaside) and tolerates drought and pollution. Fixes nitrogen and can increase fruit yields when inter-planted in your orchard.
Just Fruits: goumi is a selected seedling with large fruit, will grow to 10 feet in height but can be trimmed shorter for hedges. Self fertile. Zones 4-9

Silverberry, Thorny Olive, Silverthorn

GOLDEN SILVERBERRY (Eleagnus pungens)Eleagnus pungens – some named varieties
Zones 7-10
RollingRiverNursery Good info


Ty-Ty Nursery

An ornamental evergreen shrub with striking yellow and green varigated leaves with silver undersides. Tasty, edible, red berries that ripen in spring instead of fall. Would make a beautiful hedge. Grows to 8-10 ft. If grown in the open and left unpruned this beautiful shrub will form a symmetrical mound of foliage that is up to 15 ft  high and 20 ft  in diameter, the ultimate size being dependent on variety and climate.

Wikipedia: Elaeagnus pungens is a dense, branching shrub which can reach over 7 metres (23 ft) tall by 4 metres (13 ft) wide. It sprouts prolifically from its stem, spreading out and twining into adjacent vegetation. Parts of the stem are covered in thorns which can be up to 8 centimetres (3.1 in) long. The evergreen, alternately-arranged leaves are up to 10 centimetres (3.9 in) long but under 5 centimetres (2.0 in) wide.

Despite its invasive potential, E. pungens is widely cultivated as a garden plant in temperate regions. It tolerates varied environmental conditions, including heat, cold, wind, coastal conditions, shade, and full sun. It is very drought-tolerant. It can grow in varied soil types, including those found at mine spoils.[3]Numerous cultivars have been developed, especially forvariegated foliage effects. Commercially availablecultivars include ‘Maculata’, which has gold coloration on the leaves,[5] as well as ‘Fruitlandii’, ‘Hosoba-Fukurin’[6] and ‘Goldrim’.[7]

Thorny elaeagnus, as it is also called, is a big and beautiful broad-leafed evergreen shrub. In the late fall and early winter it produces scores of flowers that are cream colored, bell shaped, about 0.25 in (0.6 cm) long and are held in small clusters where the leaf joins the stem. To call them drab and nondescript is an understatement. Yet they can grab your attention from hundreds of yards away with their seriously strong-scented but delightfully appealing fragrance.

pruned silverthorn shrubs
These neatly pruned silverthorns in Tallahassee, Florida are helping to stabilize this hillside – see how their roots are holding the soil while the open grassy area at the lower right shows signs of slippage.

These tiny flowers mature into dark small reddish brown fruits that have an unusual silvery textured surface. The fruits are a favorite treat for birds and are said to be edible for humans too. Floridata doesn’t list silverthorn as edible because they’re just not that good. They’re tart, seedy and not worth the effort – leave them for the birds. If you’re looking for edible, consider the silverthorn’s cousin the gumi or cherry elaeagnus (Elaeagnus multiflora) which is a tasty treat.

Silverthorn doesn’t have actual thorns and actually there aren’t that many of these non-thorns on the plants anyway. This plant has the interesting trait of forming newly emergent branch stems into very pointed stiff 1 in (2.5 cm) spikes that feel very much like thorns if you jam one into your flesh.

Autumn Olive

Eleagnus umbellata – Autumn olive, Zones 3-9
(Considered invasive in many places.)
Read: The Views of Autumn Olives

Nitrogen-fixing shrubs/trees @ BurntRidgeNursery

Sea Buckthorn

Nitrogen fixer, but not a good choice for Texas caliche soils. It needs lots of moisture.

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