The black locust (Robinia pseudoacacia), or false acacia, carries very fragrant bunches of white or red flowers that bees work over relentlessly, above green leaves that shimmer and sway on the branch. Fast-growing, long-lived and prized for timber that naturally resists rot and insects, it blooms best in full sun.
| Name | Robinia pseudoacacia |
|---|---|
| Family | Fabaceae |
| Type | tree |
| Height | 30 to 50 feet (10 to 15 meters) |
| Exposure | full sun |
| Soil | ordinary |
| Foliage | deciduous |
| Flowering | early summer |
| Fruit formation | summer |
Plant preferably in fall to favor root development before winter and proper regrowth in spring.
If purchased in a container, you can also plant it in spring, taking great care to increase watering at the beginning.
Beyond the plain species, a handful of robinias are widely sold, from full-size shade trees to mop-heads and shrubs for tight corners. Height and flower colour are what usually decide the choice.
| Variety | Height | Flowers | Best for |
|---|---|---|---|
| ‘Twisty Baby’ | 8–12 ft (2.5–4 m) | Sparse, white | Contorted winter branches in pots and tiny plots |
| ‘Purple Robe’ | 40 ft (12 m) | Deep rose-pink | Flower colour on a full-size shade tree |
| ‘Umbraculifera’ | 20 ft (6 m) | Rarely flowers | Small gardens and formal umbrella crowns |
| ‘Frisia’ | 40 ft (12 m) | White, scented | Golden-yellow foliage all season |
| ‘Bessoniana’ | 40 ft (12 m) | White, sparse | Thornless trunk near paths and play areas |
| ‘Hillieri’ | 25 ft (8 m) | Lilac-pink, fragrant | A medium tree with scented pink bloom |
No specific pruning is required, but it is important to remove dead or weak branches whenever you notice them.
It is also possible to restrict this tree’s growth by pruning it or removing larger branches in fall.
Black locust wood naturally resists rot and insects. It is excellent to make fence posts and other garden items from.
A raised garden bed made from black locust will last decades. Use slabs of black locust to make edges in your raised garden. Unlike regular logs, these won’t need to be replaced every three or four years.
Many stores sell swing sets made from chemically treated wood or metal, but black locust is a perfect alternative.
It’s also possible to build a terrace with black locust. Simply check with the supplier that the wood comes from heartwood, not sapwood.
Black locust has a tendency to warp and twist upon drying.
Also, black locust is slightly more brittle than other woods.
Black locust tree got its scientific name Robinia from its inventor or discoverer Jean Robin, the royal botanist of Henry the IVth of France who planted it for the 1st time Place Dauphine, in Paris, in 1601.
Native to the United States of America, false acacia, which also goes by the common name black locust tree, is a very elegant tree with a balanced bearing. Its hardiness leads it to live a very long life.
Fruits form pods and come from flowers that cluster in very fragrant bunches of white or red when they appear in June.
The green leaves may fall off in fall without even having turned brown. They shimmer and sway and make this tree look alive.
An interesting variety stays smaller as it grows. It’s called Robinia pseudoacacia ‘Umbraculifera’, because the canopy looks similar to an umbrella!
Upon planting, spread some mulch at the base of the tree and you’ll avoid weed growth!
