Locust

Robinia

A genus of around 20 species of deciduous shrubs and trees, that are part of the larger Legume family and are all native to North Americas.
The flowers are the only part of the plant that is edible and can be eaten raw in salads or fried in tempura batter.
Black Locust can be grown commercially for pulpwood and coppiced, especially on steep slopes where the roots stabilize the earth.
They prefer full sun on most well drained soils. Most are very tolerant of drought, poor soil, saline soil and pollution. The Locust(s) love hot summers but will also tolerate cooler climates. Tree forms should be pruned when young to encourage a strong scaffold, since otherwise they can be somewhat brittle with branches breaking in high winds. Prune during early fall...trees pruned during spring will bleed profusely. They are often defoliated by leaf miner in some areas.
The Robinias can be reproduced from seed ( viable up to a decade or more ), root cuttings, suckers or cuttings. The seed should be soaked in hot water before sowing to soften the seed coat. Species that sucker can also be propagated from separated suckers.

Robinia x ambigua
A fast growing, medium-size tree that is the hybrid between Acacia pseudoacacia & A. viscosa.
Some records include: 12 years - 56 feet; largest on record - 70 x 50 feet with a trunk diameter of 2 feet.
The pinnate leaves, up to inches in length, are composed of 7 to 23 leaflets, up to
The foliage is deep green.
The light pink flowers, up to 1 inches, are borne in racemes, up to 8 inches in length, during early summer.
The young stems are somewhat sticky, with smaller thorns than Acacia pseudoacacia.
Hardy zones 3 to 9. Drought tolerant.

* historic archive photo

'Decaisneana'
A very handsome tree with rose-pink flowers. Some records include: 41 years - 53 feet with a trunk diameter of 40 inches; largest on record - 80 feet.
Prefers hot summers.

'Idahoensis' ( Idaho Locust )
The fragrant pinkish-purple flowers are borne in racemes up to 8 inches in length.

Robinia boyntonii
A fast growing, thornless medium size shrub native to the southeast U.S. from Tennesee to North Carolina; south to Alabama to Georgia. Some records include: largest on record - 10 feet.
The pinnate leaves, up to 10 inches in length, are composed of 7 to 15 leaflets, up to 2 x 1 inches.
The purplish-pink and white flowers are borne in loose racemes, up to 4 inches in length
Hardy zones 4 to 9, it thrives at Dominion Arboretum in Ottawa, Canada but is usually rarely seen outside it's native range.

Robinia hispida ( Rose Acacia )
Also called Bristly Locust. A fast growing, dense, bushy, upright to arching large shrub to around 6 to 10 feet that is native to dry woodlands in the southeast U.S. ( from western Kentucky to much of Maryland; south to southern Alabama to southern Georgia ) where it often forms a dense thicket of suckers. It is endangered in the wild in Maryland. It has naturalized locally in Nova Scotia. Some records include: 10 years - 8 x 8 feet; largest on record - 13 x 30 feet. It does have invasive potential on some sites. It is great for shelterbelts, highway plantings as well as stabilizing sand dunes and strip mines. It also makes an impressive flowering plant for the larger residential landscape.
The pinnate leaves, up to 12 inches in length, are composed of 7 to 19 bristle-tipped leaflets, up to 2.4 inches in length.
The foliage is deep green above, gray-green beneath.
The very showy, profuse, fragrant pinkish-purple flowers, up to 1 inch, are borne in racemes, up to 5 inches in length, during late spring. It rarely sets seed.
The thornless stems are covered in red bristles that cause irritation when they stick to the skin.
Hardy zones 3 to 9; it can be grown in the entire central and eastern U.S. and southern Ontario to Nova Scotia, Canada as well. In the west; it grows in eastern Washington & Oregon as well as Salt Lake City, Utah. propagation is from seed, suckers separated from main plant or root cuttings taken during winter.

* photos of unknown internet source



'Arnot'
A very attractive, vigorous USDA cultivar of Robinia hispida subsp fertilis deserving much wider use.

* Photos courtesy of USDA NRCS.

'Macrophylla'
Large pink flowers, each up to 1.6 inches. The stems also have no bristles, making this a much more desirable ornamental plant.

* photos taken by Milan Havlis, owner of central Europe's premier plant nursery

'Monument'
Larger growing, dense and more treelike, reaching up to 18 feet. Some records include: 20 years - 23 x 13 feet; largest on record - 40 x 40 feet with a trunk diameter of 1 foot.

'Rosea'
Darker flowers, otherwise identical to the species.

* photos taken by Milan Havlis, owner of central Europe's premier plant nursery

Robinia x holdtii
A broadly-columnar, medium-size tree that is the hybrid between Robinia luxurians & R. pseudoacacia. Some records include: fastest recorded growth rate - 6 feet; potential maximum size - 100 x 70 feet with a trunk diameter of 6 feet ( usually half that ).
The pinnate leaves, up to 18 inches in length, are composed of 17 to 21 oblong leaflets, up to 2 x 1 inches. The foliage is purplish at first, turning to deep green above, gray-green beneath.
The white with purplish-pink flushing flowers, up to an inch, are borne in hanging clusters, up to 8 inches in length, from July through September.
They are followed by a reddish, bristly pod, up to 3 inches in length.
Hardy zones 3 to 9. Extremely heat tolerant.

'Britzensis'
Some records include: 20 years - 30 feet; largest on record - 66 feet with a trunk diameter of 2 feet.
It can live over 100 years.
The foliage is gray-green and the flowers are pinkish-white to white.

'Purple Robe'
A very beautiful fast growing tree for hot dry sites. Some records include: 20 years - 50 x 32 feet; largest on record - 53 feet with a trunk diameter of 20 inches. It is a hybrid between Robinia ambigua 'Decaisneana' and R. hispida 'Monument'.
The very attractive foliage is red-purple during spring, turning to bronze-green during summer, then to yellow in autumn.
The red-purple flowers are borne on racemes.
Hardy zones 3 to 9, it is recommended that is be grown on its own roots to prevent reversion through suckering..

* photo taken on Sep 22 2015 in Columbia, MD

* photo taken on Nov 10 2020 @ Brookside Gardens, Wheaton, MD

* photos taken on Aug 7 2023 in Columbia, MD

Robinia kelseyi ( Kelsey Locust )
Also called Alleghany Moss Locust
A fast growing, large shrub, very similar to Robinia hispida, except the branches loose their bristles after time, plus in having leaves with fewer leaflets.
Some records include: 20 years - 17 x 13 feet; largest on record - 60 x 13 feet. This Locust is not invasive.
The pinnate leaves, up to 6 inches in length, are composed of 7 to 11 leaflets, up to 2 x 0.7 inches.
The foliage is
The fragrant pink flowers are followed by fruits that are covered in purple hairs.
Hardy zones 5 to 9, thriving as far north as Ottawa, Ontario.

Robinia luxurians
A small tree, that is native to the southeastern U.S. Some records include: 17 years - 22 feet; largest on record - 63 feet with a trunk diameter of 26 inches. It can exceed 100 years of age.
The leaves, up to 12 inches in length, are composed of up to 21 oblong leaflets, up to 1.5 inches in length.
The rose-pink ( later fading to pinkish-white ) flowers are borne on dense racemes up to 8 inches in length.
Hardy zones 5 to 9. Thrives in England.

Robinia neomexicana ( New Mexico Locust )
A rare fast growing, small to medium size tree native to the southwestern U.S. from central Nevada to central Wyoming; south to southeast Arizona to El Paso, TX to the far western tip of the Oklahoma Panhandle. Some records include: 3 years - 15 feet; 8 years - 20 feet; largest on record - 81 x 35 feet with a trunk diameter of 3.4 feet.
The pinnate leaves, up to 12 inches in length, are composed of 13 to 25 oblong leaflets, up to 1.7 inches.
The foliage is covered in fine gray hairs at first, turning to smooth and blue-green.
The bright pink to purple-pink flowers are borne in hanging racemes, up to 4 inches in length, during summer. The flowers are edible and the Pueblo Indians eat them uncooked.
They are followed by flattened pods, up to 3 inches in length, that are unique because they are covered in bristly hairs.
The deeply-furrowed bark is light gray. The spine armed twigs are almost identical to that of Robinia pseudoacacia.
Hardy zones 3 to 9. Extremely hardy, it grows well anywhere between Michigan and Tucson, Arizona. Heat and drought tolerant.

* new mexico locust in Fallon, NV

* new mexico locust in Elko, NV

* new mexico locust in Pioche, NV

* new mexico locust in Virginia City, NV

* photo taken by W.A. Jackson @ USDA-NRCS PLANTS Database

* USDA-NRCS PLANTS Database

* historic archive photo

Robinia pseudoacacia ( Black Locust )
A upright, open and rounded large tree native to central and eastern U.S. from eastern Nebraska to Pennsylvania; south to Oklahoma to northern Georgia. It is also commonly planted in other parts of the U.S. and eastern Canada where in many places has spread into the wild. It is also naturalized locally in western, central & southeastern Europe and in Ontario as far north as Sault Ste Marie as well as in southern British Columbia and Nova Scotia. Some records include: fastest recorded growth rate - 10 feet; 1st year - 2 feet; 3 years - 18 feet; 10 years - 50 feet; 20 years - 70 x 60 feet; 30 years - 82 feet; 40 years - 86 feet; 60 years - trunk diameter of 4.5 feet; largest on record - 172 x 90 feet with a trunk diameter of 8.7 feet; largest in Canada - 120 x 70 x 5.5 feet in Bayfield, Ontario; longest lived - 412 ( very rarely over 200 ) years. The Black Locust often suckers to form colonies, especially if the parent tree is cut while dormant. Some of the best examples of large Black Locust are in Europe and parts of Canada outside the reach of the borer that frequently attacks this tree.
The roots of the Black Locust fix their own nitrogen and lawns grow well in the light dappled shade beneath.
The pinnate leaves, up to 14 inches in length, are composed of 11 to 23 smooth-edged, oval leaflets, up to 2 x 1 inches in size. The foliage is bright green at first, turning in summer to blue green above, pale gray-green beneath. The leaves turn to yellow late in autumn though some trees turn only to gray-green before falling. The leaves and any other parts of this plant, are highly toxic if eaten by horses.
The very fragrant white flowers, up to 1 inch, are borne in dense drooping racemes, up to 14 ( rarely over 8 ) inches in length, during early summer. The flowers attract bees and are important to Honey production.
They are followed by dark brown, flattened, hanging seed pods, up to 4 x 0.5 inches, that often persist into winter. Each pods contains 4 to 8 seeds.
The thorny young stems are reddish. The thorns are up to 0.5 inches in length.
The light brown to blackish bark on older trees is deeply furrowed with very rugged interlacing ridges.
The wood is among the hardest and heaviest ( 50 pounds per square foot ) of all trees in North America.
It is resistant to rot ( lasting decades ), extremely hard and durable, making it valuable for furniture, panelling, flooring and fence posts. The firewood is excellent for wood burning stoves, throwing off more heat ( 26 million Btu per cord ) than just about any other tree native to the eastern U.S.
Hardy zones 3 to 9; it prefer a deep sandy ,well drained soil with a PH of 4.6 to 8.2. Black Locust requires 28 + inches of average yearly rainfall to thrive. The roots of the Black Locust fix ( create their own ) nitrogen, making this an excellent tree for reforesting barren poor soil wastelands. In many areas they are prone to not only leaf miner damage to the foliage, but also trunk damage from borers. To prevent later storm damage; young trees should be pruned to a single leader and feathered ( shorten and space main limbs ).

* photos taken on May 1 2010 in Howard County, MD


* photos taken on May 5 in Columbia, MD


* photo taken on August 2 2010 in Bayfield, Ontario





* photos taken on August 4 2010 in Stratford, Ontario



* photos taken on July 31 2011 in Hyde Park, NY


* photos taken on July 25 2015 @ Niagara-on-the-Lake, Ontario

* photo taken on Jun 14 2016 in Columbia, MD

* photo taken on July 14 2016 in Tobermory, ON

* photos taken on July 16 2016 in Bayfield, ON

* photos taken on Sep 17 2016 in Annapolis, MD

* photo taken on May 15 2018 in Columbia, MD

* photos taken on May 25 2018 in Howard Co., MD

* photos taken on July 14 2018 in Bayfield, ON

* Black Locust on Manitoulin Island

* Black Locust in Port Burwell, ON

* Black Locust in Bothwell, ON

* Black Locust in Oakville, ON

* photo taken on Feb 27 2019 in Ellicott City, MD

* photos taken on Aug 22 2021 in Bayfield, ON

* photo taken on Aug 23 2021 in Grand Bend, ON

* photos taken on July 9 2022 in Bayfield, ON

* photos taken on July 7 2023 @ Bayfield, ON

* photos taken on Aug 16 2024 in Bayfield, ON

* photo taken by W.R. Mattoon @ USDA-NRCS PLANTS Database

* photo taken by Edward H. Wollerman @ USDA-NRCS PLANTS Database

* USDA-NRCS PLANTS Database

* historical archive photos

* historic archive photo of 4 year plantation

'Appalachia'
Narrowly erect with a strong straight trunk. Some records include: 16 years - 43 feet with a trunk diameter of 15 inches.

'Aurea'
Foliage is greeish-yellow during spring, turning to light green during summer. Known to reach up to 53 feet with a trunk diameter up to 40 inches.

'Bessoniana'
A vigorous, nearly thornless form that is upright to rounded, reaching a maximum size of 60 x 30 feet with a trunk diameter of 37 inches.

* photos taken on Oct 31 2013 @ Hampton Ntl. Historic Site, Towson, MD

* photos taken on July 25 2015 @ Niagara-on-the-Lake, Ontario

* photos taken on Jul 18 2017 @ Dominion Arboretum, Ottawa, ON

'Frisia'
A fast growing broadly columnar tree reaching around 40 feet. Some records include: 5 years - 33 feet with a trunk diameter of 7 inches; 24 years - 50 feet with a trunk diameter of 2 feet; largest on record - 80+ feet. It is thornless and sparsely flowered, having bright golden-yellow spring foliage that turns to yellow-green during summer then to orangish-yellow during fall.

* photo taken on annual Horticultural Society of Maryland Garden Tour


* photo taken on Aug 25 2011 @ Scott Arboretum, Swarthmore, PA

* photos taken on May 27 2017 @ Meadowlark Botanical Gardens, Vienna, VA

* photos taken on Jul 18 2017 @ Dominion Arboretum, Ottawa, ON

* photos taken on Aug 5 2017 @ Brookside Gardens, Wheaton, MD

* photos taken on Aug 1 2022 in Brookside Gardens, Wheaton, MD

* photos taken on July 10 2024 @ Brookside Gardens, Wheaton, MD

'Inermis'
Thornless; otherwise identical to species.

'Lace Lady'

* photos of unknown internet source


'Monophylla'
Leaves, up to 4 x 2 inches, are simple meaning singular rather than pinnate with leaflets.

* photos taken on July 17 2010 @ Morris Arboretum, Philly, PA



* photos taken on Jul 18 2017 @ Dominion Arboretum, Ottawa, ON

'Rozynskyana'
Same size as species, it is extremely graceful with pendulous branch tips and long leaves, up to 20 inches in length. It looks somewhat like a Weeping Willow and deserves much wider use.
The very abundant flowers are fragrant and white.

'Semperflorens'
Vigorous and reaching about the same size as the species.
It blooms very heavily with a second continuous bloom from mid-summer on.

'Tortuosa'
Has twisted branches and a "natural bonsai-like habit". Some records include: largest on record - 37 x 20 feet with a trunk diameter of 38 inches.

* photos taken on Jul 18 2017 @ Dominion Arboretum, Ottawa, ON

* photo taken on Apr 16 2023 @ Fort Hunter, Harrisburg, PA

Robinia x slavinii
The hybrid between Robinia kelseyi and R. pseudoacacia, forming a small to medium-sized tree. Some records include: largest on record - 60 feet with a trunk diameter of 22 inches. The foliage is bristly.
The rosy-pink flowers are borne on racemes.
Hardy zones 5 to 8.

Robinia viscosa ( Clammy Locust )
A rare fast growing, small tree native to the southeast U.S. mostly in the Appalation Mountains from northern Alabama to central Pennsylvania. It is the prettiest of all Robinias and is also cultivated in England and central Europe where it thrives. It has been reported by botanic text "The Vascular Flora of the Bruce Peninsula" to be locally naturalized near Wiarton, Ontario...which would be a most welcome addition to their local flora. Some records include: 20 years - 27 feet; 24 years - 40 feet with a trunk diameter of 21 inches; largest on record - 60 x 40 feet with a trunk diameter of 1.7 feet.
The pinnate leaves, up to 12 inches in length, are composed of 13 to 25 leaflets, up to 2 x 1 inches. The foliage is deep green above, gray hairy beneath; turning to golden-yellow in autumn.
The pink flowers, up to inches, are borne in dense racemes, up to 3 inches in length, borne during late spring.
They are followed by brown seed pods up to 4 inches in length.
The very sticky, dark brown young stems are only armed with a few thorns.
The bark is smooth and reddish-brown.
Hardy zones 3 to 8.

* photos taken on Jul 18 2017 @ Dominion Arboretum, Ottawa, ON

* photos taken on May 10 2021 in Columbia, MD

* USDA-NRCS PLANTS Database

* historic archive photo