A tough Native American deciduous tree hardy from zones 3-9A. Best known for its amazing display of extremely aromatic flowers that often totally cover the tree in mid spring. Much loved by bee keepers since the bees adore this high nectar tree and can produce a lot of honey just from these flowers. A member of the legume family this tree fixes nitrogen so it aids the plants that grow beneath it. It can also grow on fairly toxic soils and its roots bind together loose soils making it perfect for soil reclamation and soil erosion. Needs full sun but not fussy about soil type but it must be well drained does not tolerate wet soils. Often used for mine sides and reclamation projects because of its fast growth and ability to shelter and feed other species that would not be able to grow there otherwise. This also helps create areas for wildlife, or just people who enjoy sitting beneath its branches. Easy to grow from seed but does need a little work to remove the tough seed coat. Fairly wildlife resistant once grown but deer will eat seedlings.
The leaves are compound the whole leaf being roughly oval in shape but made up of 3-9 pairs of smaller ovate to oblong leaflets up to 2 inches (5cm) long and 1 inch (2.5cm) wide with rounded at the ends and smooth margins. Leaves are dark green with a gentle hint of blue.
In spring just as the leaves are emerging the flowers unfold. Masses of white pea like flowers borne in dangling pendant racemes up to 8 inches (20cm) emerging from the leaf forks. Each flower is predominately white made up of five petals fused together in a tube splaying out at the front with two upper and three lower lobes the upper ones most commonly have tints of green or green lines. Each flower is borne on a stalk about 0.25-1 inch (5-10mm) long in clusters of 10-30 flowers. The amount of flowers the tree produces will vary by year, some years the whole tree is covered. Flowers are followed by elongated and flattened pod up to 5 inches (13 cm) long and 0.5 inches (15 mm) wide that turns from green to brown in colour as it matures and contains from 4-8 small bean-like seeds. Pods often remain on the tree late into the fall and may even remain over the winter months in some zones.
Trees have a roughly oval shape with rough upward forming branches. The wood is very dense and thus not flexible in younger branches. This makes the tree strong and stable but branches will break if pulled on rather than bend.
Black locust is part of the legume family and therefore its a nitrogen fixer. These trees will can enrich the soil around them as they produce far more nitrogen than they use.
You will need
- A sheet of course sandpaper.
- A sanding sponge course to medium course.
1. Place the sandpaper on a flat stable surface and put the seeds on it. Only use a few at a time, 5 -10 maximum. Do not process more seeds than you want to germinate at one time.
2. Use the sanding sponge to rub against the seeds rub hard, the seed coat is tough.
3. Place processed seeds in a small container. Boil some water. pour some into a different container and let it stand. The objective is to shock the seeds and crack the coating not kill them so you need very hot but not boiling water as they could kill the seeds. We found the best way to test the water is to put your index finger in it. If you can hold it there for the slow count of 5 before removing it then its cool enough for the seeds.
4. Place the seeds in the water and agitate it. The objective is to shock the seeds are crack the coating. Shake for a few moments then leave them to soak for 12-24 hours. Seeds that have cracked their coating will swell. If some have not swollen those will need retreatment.
Once seedlings have sprouted move to individual pots after true leaves form and grow on until at least 8-10 inches (20-25 cm) tall before planting out. Ensure that seedlings are introduced to full sun gradually to harden them off before transplanting. Protect new seedlings from wildlife browsing as the will commonly eat young trees.
Will need added water when transplanted until it is established and again while it is young if there is severe drought. Otherwise it is fairly drought tolerant and can grow on relatively dry soils.
This tree produces very heavy dense wood which does not rot easily. This means it rarely falls unless it has been attacked by insects or damaged. However the dense wood makes it inflexible even in smaller branches so they will not bend like many other trees do. Take care on pulling branches down to harvest flowers or any other reason the branch is likely to break off.
Black locust produces many strong surface roots, not enough to disrupt pavements and roadways but slightly deeper where it bonds the soil together. For this reason it is commonly used to bind soils on industrial sites such as quarry edges road cuts. It can also tolerate far more toxins in the soil than most other plants making it an ideal plant for such locations. That in addition to its nitrogen fixing capabilities make it an ideal initial plant for such locations. In dry soils it will produce much deeper roots giving it a solid foundation to withstand environmental conditions and strong weather.
Pruning. These trees need little pruning but avoid doing so in early spring as this can cause excessive sap bleeding that can weaken the tree and make it more prone to disease. Trees will also sucker from the roots so these need to be pruned down to keep the trees from forming thickets.
However this can also be a problem if the trees seeds spread and begin colonizing other areas as they can out-compete native plants and take over areas where they may be considered undesirable. This is especially true after fire has burnt a forest.
Care should be taken when planting this tree to ensure it is not in a location where it will be considered a menace.
These trees have been planted throughout the world because of their aromatic flowers which have a very high nectar content making them very desirable to honey bees. They will often produce whole crops of honey just from the short flowering of these trees. For this reason they may have been planted en mass in some areas then the spread can make them undesirable to others who are not bee keepers.
The large, dark seed pods provide food for quail, turkey, grouse, pheasant, and songbirds from autumn to early spring. Small wildlife often nests among the branches, utilizing the tree's thorns. Attracts deer and bees enjoy its flowers
There is also a wide variety of other insects such as locust twig borer (Ecdytolopha insiticiana) which can kill young trees. Locust borer (Megcallene robiniae) makes tunnels in the wood which can be used as entranceways by the heart rot fungi Phellinus rimosus or Polyporus robiniophilus which can kill the trees or at least make them unusable as lumber.
Depending on what zone the tree is growing in there may also be scale insects, caterpillars, whiteflies, weevils, powdery mildew, verticillium wilt, and leaf spots.
Toxicity.
All parts of the plant (except the flowers) and especially the bark, should be considered to be toxic . The toxins are destroyed by heat.
Both the inner bark and the root bark are considered emetic and is used as a purgative. There are some reports that the seedpods are narcotic.
Because of its resistance to rot using as fence posts is extremely important especially on organic farms where the use of many material is prohibited. Often whole tree limbs or small harvested trees are used as fence posts rather than processing them into traditional rectangular lumber.
It has been used extensively across the United States, Europe, and Asia for erosion control. It is considered superior to all other trees for creation of nurse crops. Black locust is fast growing and provides protection for slower growing species to flourish underneath it. Its nitrogen fixing ability also helps other plants grow especially in reclamation projects where the soil may be contaminated with toxins. Growing fast they provide habitat for many wildlife species including game birds, deer, squirrels, and many smaller rodents. Deer like to browse the small seedlings.