ENH-731

Robinia pseudoacacia ‘Umbraculifera’: Umbrella Black Locust1

Edward F. Gilman and Dennis G. Watson2

1. This document is ENH-731, one of a series of the Environmental Horticulture Department, UF/IFAS Extension. Original publication date November 1993. Revised December 2006. Reviewed February 2014. Visit the EDIS website at http://edis.ifas.ufl.edu.

2. Edward F. Gilman, professor, Environmental Horticulture Department; and Dennis G. Watson, former associate professor, Agricultural Engineering Department, UF/IFAS Extension, Gainesville, FL 32611.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county’s UF/IFAS Extension office. U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.

IntroductionA fast-growing deciduous tree, umbrella black locust grows to about 20 feet tall and wide. The weeping, round habit forms a canopy much denser than the species casting dense shade below the tree. The 6- to 14-inch-long, dark green leaves, made up of multiple leaflets, are some of the last to appear in spring and often drop early in the autumn. Flowers irregularly with only a flower ‘here and there’ in the crown. The 2- to 4-inch-long, dark red to black, leathery seeds pods which sometimes follow will persist on the trees throughout the winter.

General InformationScientific name: Robinia pseudoacaciaPronunciation: roe-BIN-nee-uh soo-doe-uh-KAY-shuhCommon name(s): Umbrella black locust, umbrella common locustFamily: LeguminosaeUSDA hardiness zones: 4A through 8B (Fig. 2)Origin: native to North AmericaInvasive potential: weedy nativeUses: specimen; shadeAvailability: not native to North America

Figure 1. Mature Robinia pseudoacacia ‘Umbraculifera’: umbrella black locustCredits: Ed Gilman, UF/IFAS

Figure 2. Range

2Robinia pseudoacacia ‘Umbraculifera’: Umbrella Black Locust

DescriptionHeight: 15 to 20 feetSpread: 20 to 25 feetCrown uniformity: symmetricalCrown shape: weeping, roundCrown density: denseGrowth rate: fastTexture: fine

FoliageLeaf arrangement: alternate (Fig. 3)Leaf type: odd-pinnately compoundLeaf margin: entireLeaf shape: elliptic (oval), oblong, obovateLeaf venation: pinnateLeaf type and persistence: deciduousLeaf blade length: less than 2 inchesLeaf color: greenFall color: yellowFall characteristic: not showy

FlowerFlower color: no flowersFlower characteristics: no flowers

FruitFruit shape: no fruitFruit length: no fruitFruit covering: no fruitFruit color: no fruitFruit characteristics: does not attract wildlife; no fruit; fruit/leaves not a litter problem

Trunk and BranchesTrunk/bark/branches: branches droop; showy; typically one trunk; thornsPruning requirement: needed for strong structureBreakage: susceptible to breakageCurrent year twig color: brownCurrent year twig thickness: thinWood specific gravity: 0.69

CultureLight requirement: full sun, partial sun, or partial shadeSoil tolerances: clay; sand; loam; acidic; alkaline; well-drainedDrought tolerance: highAerosol salt tolerance: high

OtherRoots: can form large surface rootsWinter interest: yesOutstanding tree: noOzone sensitivity: unknownVerticillium wilt susceptibility: susceptiblePest resistance: sensitive to pests/diseases

Use and ManagementThe tree is best used as a specimen for an outstanding ornamental effect. Plant on 20- to 30-foot-centers along an entrance road or along highway medians. This should be a very adaptable, pretty tree for urban plantings, but is usually not grown by nursery operators. The root suckering and invasive root system allows the species to quickly spread into surrounding landscapes. This feature should be considered when placing black locust in the ornamental garden, although the cultivar may not sucker as much.

Although the wood of black locust is reputed to be extremely strong and durable (pioneers used it to fashion nails for building ships and houses), the branches are brittle and subject to damage in high winds. This may be due largely to the tendency for the branches to form a narrow angle with the trunk and to grow aggressively relative to the trunk. This can be partially corrected by pruning the major branches so they grow to no more than about half the size of the trunk. Try to space the major branches along the trunk as best you can to develop a strong tree which will stay together. This will be difficult since the tree is usually purchased with the major branches well developed and most of them originate from one point on the trunk. Able to tolerate drought, salt, and poor soil, black locust will grow in full sun or partial shade on almost any soil except that which is permanently wet. The species is a tough tree which will grow on the toughest sites, and there is no reason to believe this cultivar will respond differently.

PestsLocust borer is a serious pest although borer-resistant clones are now being developed. Also bothered by carpenterworm, locust leaf miner, and scales. Leaf miner is a universal problem on the species, and the trees along the

Figure 3. Foliage

3Robinia pseudoacacia ‘Umbraculifera’: Umbrella Black Locust

highways in the south can be seen in summer riddled with damage from this pest.

DiseasesThis tree is susceptible to canker, leaf spot, and powdery mildew.