honey locust

not listed

N5 - Secure

SNR - Unranked

not listed

FACU - Facultative upland

FACU - Facultative upland

FAC - Facultative

Honey locust is a fast-growing, moderately long-lived, deciduous tree rising on a single trunk from a strong taproot and a deep, profusely-branched, wide-spreading root system. Unlike most trees, this species has root hairs. In Minnesota, mature trees are usually 40′ to 60′ tall and up to 18″ in diameter at breast height, though large individuals can reach over 80′ in height and 36 ″ in diameter. A thornless form (f. inermis) is widely cultivated but occurs only sporadically in nature.

The trunk is short and is often divided in the lower half of the tree’s total height. The trunk and major branches are armed with long, conspicuous thorns, often in clusters. The thorns are deep brown, stout, slightly flat, ¾″ to 8″ long, and often branched (compound).

The crown is broad, open, and often flat-topped. The branches are slender and spreading or ascending. They are armed with thorns that are 1″ to 4″ long, 1 ⁄16″ to ⅛″ in diameter at the base, and often with many-branched.

The bark on young trunks is reddish-brown and smooth with numerous dark, horizontal lines (lenticels). On mature trunks the bark is light gray to dark gray or nearly black, deeply furrowed, and broken into long, narrow, scaly plates.

There are two kinds of shoots (young twigs): long, shoots with alternate leaves, and short shoots, barely clearing the bark, with clustered leaves. The long shoots are somewhat zigzag, green, and hairy at first, eventually becoming hairless, reddish-brown, and shiny. Twigs are may be either stout or slender. They are armed with smooth, reddish-brown, 1″ to 3″ long, often 2-branched, sometimes 3-branched, thorns. The thorns appear singly at the nodes.

There is no terminal bud. Lateral buds are small and are hidden beneath the leaf scar, often appearing as small knobs. The leaf scars are U-shaped and have 3 bundle scars.

Two types of leaves are produced: early leaves, also called preformed leaves; and late leaves, also called neoformed leaves. The leaf stalk (petiole) of both types of leaves is 4″ to 8″ long and distinctly short-hairy. The central axis (rachis) is light green and short-hairy.

Early leaves are fully formed and overwinter in the bud. They are the first leaves to mature in the spring. They are produced on short, preformed shoots and at the base of long, partially preformed, partially neoformed shoots. They are 4¾″ to 5½″ long and singly, evenly, pinnately compound, divided into 7 to 16 pairs of leaflets with no terminal leaflet. The leaflets on these leaves are narrowly egg-shaped, ⅜″ to 1½″ long, and ¼″ to 9 ⁄16″ wide. They are on very short, about 1 ⁄32″ long stalks (petiolules). They are widest near the base, rounded or broadly angled at the base, and rounded at the tip. The upper surface is green or dark green and hairless. The lower surface is pale green and short-hairy at least along the midvein. The margins are very finely toothed.

Late leaves are formed at the end of long shoots. They are twice evenly, pinnately compound, divided into 4 to 7 pairs of branches (pinnae). Each pinna has 5 to 10 pairs of leaflets and resembles a once pinnate leaf. The leaflets on these leaves are somewhat smaller, narrowly egg-shaped to egg-shaped, ½″ to 1″ long, and ¼″ to ½″ wide. They otherwise resemble leaflets on singly compound leaves.

Male and female flowers are borne on the same plant, usually in separate inflorescences and often on separate branches, though some inflorescences have both male and female flowers. The inflorescences appear in the leaf axils of short shoots in late May to late June with the leaves. Each inflorescence is a 2″ to 3½″ long, spike-like, branched cluster (raceme). The female inflorescence has fewer, more widely spaced flowers than the male.

The flowers are small and inconspicuous. They have 3 to 5 sepals and 3 to 5 petals. The sepals are 1 ⁄16″ to ⅛″ long and are similar in color to the petals. The petals are about 1 ⁄16″ long and yellowish green. Male flowers have 5 to 8 stamens with 1 ⁄16″ to ⅛″ long filaments. The female flower has a short style with with a 2-lobed stigma. The flowers are fragrant.

The fruit is a 7″ to 16″ long, 1″ to 1½″ wide, strongly flattened, usually spirally twisted pod with many seeds. The pod is green at first, and the seeds are embedded in a thick, sweet, jelly-like pulp. They eventually turn purplish-brown and the pulp becomes dry and inconspicuous. The fruit ripens in late August to late September and remains on the tree through the winter. The seeds are dispersed by animals.

40′ to 80′

The champion honey locust in Minnesota is on public property near Fairmont, in Martin County. In 1999 it was measured at 80′ tall and 168″ in circumference (53½″ in diameter), with a crown spread of 83′.

Yellowish-green

Black locust (Robinia pseudoacacia) has a pair of short spines at the base of each leaf but is otherwise thornless. The leaflets are much larger, ¾″ to 2⅜″ long, and ⅜″ to 13 ⁄16″ wide. The inflorescence has large, showy, white, pea-like flowers. The fruit is much smaller, no more than 4″ long and ⅝″ wide.

Kentucky coffee tree (Gymnocladus dioica) has no thorns. The leaflets are much larger, 1½″ to 3½″ long, and ¾″ to 13 ⁄16″ wide. The fruit is much smaller, no more than 6″ long, and is thick, not strongly flattened.

Moist. Shade intolerant. Bottomlands, parks, and old homesteads.

Late May to late June

Sources

2, 3, 4, 5, 7, 8, 22, 24, 28, 29, 30.

Native

Rare and scattered. Native probably extirpated.

There may be no native honey locust trees left in the state. The last known naturally occurring tree was submerged behind lock and dam number 8 on the 1930s. Mosty existing specimens are likely cultivars planted in parks or near homes following European settlement in the last half of the 19th century. Cultivars currently popular with landscapers have no thorns and produce no fruit. The single tree in Vermillion Highlands Research Recreation and WMA does have thorns on the branches and on the trunk.

Two forms are recognized. The nominate form, Gleditsia triacanthos f. triacanthos, has long thorns on the branches and on the trunk. A cultivated form, Gleditsia triacanthos f. inermis, has no thorns.

Just noticed this week, the seed pods all came off this huge old tree. It is located in the back yard of a neighbor, at the intersection of 15th ave n, and 3rd ave. in St. Cloud.

Honey locust bearing fruit

Thorns on a honey locust

Tree

Thorns

Fruit

Location: River Edge, NJ

Location: St. Cloud, MN

Just noticed this week, the seed pods all came off this huge old tree. It is located in the back yard of a neighbor, at the intersection of 15th ave n, and 3rd ave. in St. Cloud.

Location: Midway area, St Paul, near Hamline U

Huge tree.  I gather the dried fruit each fall.

there are several smaller ones nearby.

Location: Albert Lea, MN

Honey locust bearing fruit

Location: near MN/IA border

Thorns on a honey locust near MN/IA border

Location: Saint Paul, 55116

This tree is growing in our back yard. We didn't know what it was until today.