Common Name: Black Locust, False Acacia
Scientific Name: Robinia pseudoacacia
Family: Fabaceae (the Legume, Pea, or Bean family)
Black Locust is native to the southeastern United States, and is a great overstory tree as it allows a lot of light through to the understory. Black Locust is a prized as a timber tree, firewood tree, and honey plant (bees love them!). It is also well-known for fixing nitrogen into the soil. Black Locust is one of the most useful and ideal trees for a Temperate Climate farm or homestead.
Native to eastern North America it has been widely planted around the world and, despite its many benefits, is considered an invasive species in many locations. It is one of the world’s leading timber trees (just not in the U.S.). It remains a prime source of nectar for honeybees as well, especially in Europe.
- Black Locust heartwood is very rot resistant – fence posts can last for 70-100 years in the ground without rotting!
- Prime honey plant in Eastern Europe
- Black Locust is one of the most widely grown timber trees in the world. The wood is strong and heavy. Said to be like oak.
- The reason for the rot resistance is the presence of tyloses and extractives in the wood. Tyloses are bulges of plant tissue that make the wood water tight. Extractives are compounds found outside the cell wall of certain plants that can impart water resistance, and have antifungal properties.
USING THIS PLANT
- Wood – fuelwood. Black Locust is fast growing, very hot burning, and very slow burning firewood – reported to be similar to anthracite coal. It can also burn when not seasoned well (i.e. still wet). Keep in mind that Black Locust wood can “spit” coals when burned, due to knots and beetle damage, so it is best to use young wood (with less beetle damage) in an open fireplace or use older wood in closed fireplaces and stoves.
- Wood – stakes, poles, posts, ship building, boxes, crates, pegs, etc. (highly rot and water resistant!)
- Wood – high quality, very hard timber (comparable to oak)
- Edible Flowers – cooked. Used in fritters (flowers are battered and fried), pancakes, and floral jams. Can also be steeped to make tea or wine.
- Nitrogen Fixing Plant – this plant creates its own nitrogen through a symbiotic relationship with microorganisms (bacteria) in its roots. It typically produces an excess of nitrogen that can be used by neighboring plants. This is a leguminous plant; Black Locust inoculation group.
- General insect (especially bees) nectar plant
- Dynamic Accumulator – Nitrogen, Potassium, Calcium
- Pioneer Plant – helps reestablish overused or damaged land
- Drought Tolerant – once established
- Coppice or Pollard Plant – Black Locust coppices well, but suckers more freely when it is coppiced. Frequency of coppicing varies on desired diameter of wood and local climate conditions
- Biomass Plant – very fast growing plant can produce large amounts of organic matter in a short time.
- Erosion Control Species – the fibrous root system helps stabilize soils prone to erosion, especially on banks
- Wildlife Shelter Plant – mainly birds and small mammals
- Hummingbird Plant – this plant has nectar that attracts Hummingbirds
- Lacewings prefer to lay eggs on this plant’s leaves.
- Parasitoid Wasps prefer to rest and hide in/on this plant.
- Fodder/Forage Plant – leaves contain 23-24% protein and is comparable to alfalfa. Used in Korea, Bulgaria, Nepal, and India for cattle, sheep, goats, chickens, rabbits, etc.. There exists some controversy on this topic. Many people feed Black Locust to their livestock with no issues. Other avoid it due to reports of toxicity. I really am not sure where the truth lies, but I lean toward it being an ancillary forage. Most likely, if the animals have access to mixed forage, Black Locust should cause no problems. However, it is universally considered toxic to horses.
DESIGNING WITH THIS PLANT
AHS Heat Zone: 9-3
Chill Requirement: not applicable
Plant Type: Large Tree
Leaf Type: Deciduous
Forest Garden Use: Canopy Layer
Cultivars/Varieties: There are a number of varieties available.
Pollination: Self-fertile. Pollinated by bees.
Flowering: Spring to Summer (April-June)
- Years of Useful Life: No good information available; however, one reference stated Black Locust can live to 200 years of age. Considering that the tree is typically harvested for wood well before it reaches its maximum lifespan, this information may not be that important.
PHYSICAL CHARACTERISTICS OF THIS PLANT
Roots: Fibrous with suckers (sends up new plants from underground runners)
Growth Rate: Fast
GROWING CONDITIONS FOR THIS PLANT
Shade: Tolerates light shade
Moisture: Grows well in dry to moderate moisture soils.
pH: 5.1-8.5 (tolerates a wide range of soil conditions)
Special Considerations for Growing:
- Black Locust are one of the few plants that tolerate juglone, a chemical produced by black walnuts that can poison other plants, so consider using these trees as a buffer plant between your black walnuts and your other forest garden plants.
- Black Locust leaves are small and allow a lot of light through to the understory plantings. Consider growing sub-canopy and shrubs here that need more nitrogen and are less shade tolerant.
- The Locust Borer (Megacyllene robiniae) is a beetle which is native to the southeastern U.S. where the Black Locust originates. The larvae riddle the trunk and branches with tunnels making the wood unfit for timber, and this pest was responsible for reducing the Black Locust’s significance as a commercial timber tree in the United States. Black Locust will grow well for many years, but rarely get large enough for timber due to this pest’s activity. Maintaining healthy, vigorous trees and promoting Locust Borer predators seem to significantly minimize borer damage, but this is uncommon. Insecticides seem to be the first choice and recommendation for dealing with Locust Borers. I am planning on living in Tennessee, right in the middle of Black Locust and Locust Borer territory. I am curious if an integrative farm, especially one that purposely attracts beneficial insects and birds (including Wheel Bugs (Arilus cristatus), Downy Woodpecker (Picoides pubescens), and Hairy Woodpecker (Picoides villosus) which prey on these larvae), would have better success in producing timber-quality trees. We will see…
Easily from seed (not dormant, but may have increased germination rates if cold stratified for a few weeks). Scarification is recommended – 48 hours in warm water. Suckers can be divided while the plant is dormant. Also easily propagated from root cuttings.
Will need to manage suckers, especially if the Black Locust is being coppiced.
- Expansive – Black Locust can form a thicket from shoots arising from rootss
- Dispersive – Black Locust seeds spread easily.
- Thorny – Not as thorny as the Honey Locust (a distant relative)
- Branches can be brittle and easily broken in strong winds.
- Poisonous – Reports exist that bark, leaves, seeds can cause vomiting and diarrhea. There are some reports that the seeds and seedpods are edible, but there is too much conflicting information (and much better food sources) to experiment. Black Locust is poisonous to horses.
- Allelopathic – Black Locust may release chemicals into the surrounding soil that inhibit the growth of other plants. Not a lot of information is available on this topic.
Here’s a video by Paul Wheaton (from Permies.com):
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