Download Gleditsia triacanthos POTW

Of interest this week at Beal...
Honey locust
Gleditsia triacanthos
Family: the Bean family, the Fabaceae
W. J. Beal
Botanical Garden
The honey locust, Gleditsia triacanthos, is a large shade tree native to the central
United States west of a line extending from New Orleans to central Pennsylvania to the
eastern thirds of Nebraska, Kansas, Oklahoma, and Texas. In most of its native range
it develops large branched thorns, hence the species name, ‘triacanthos’ (three-parted
thorns). Its Latin genus name, Gleditsia, is a tribute to the German botanist Johann
Gottlieb Gleditsch. The author (Peter Carrington) wonders whether tribute is the
right word, as Gleditsch was a prominent contemporary opponent of Linnaeus, who
assigned the name (was this an editorial comment about ‘thorniness’. . .) Almost all
modern plantings, consist of the thornless variety, inermis, that occurs naturally, or can
be cloned from the thornless upper branches of thorn-bearing specimens.
In North America, as well as in many temperate nations abroad, honey locust is an
ubiquitous street tree, though suffering from many diseases and pests, including mimosa
webworm, Homadaula anisocentra, and the honey locust plant bug, Diaphnocoris chlorionis.
Of interest is the honey locust habit of having both singly pinnately compound leaves
(above photos; middle), doubly pinnate leaves (above photos; right), and intermediate
leaves (above photos; middle right) on the same plant.
Gleditsia flowers are small and located on inconspicuous hanging spikes. Honey locust
is polygmo-dioecious, meaning each tree is predominantly male or female, but with a
few flowers of the opposite sex occurring on most specimens.
The combination of sweet edible large pods and large thorns recalls the similar
adaptations of the African umbrella acacias (e.g. Acacia tortilis) thought to have
developed in response to sharing habitat with elephants. Connie Barlow, in her
book, The Ghosts of Evolution, Nonsensical Fruit, Missing Partners, and Other Ecological
Anachronisms, New York, Basic Books, 2000, points out that North America had
tree browsing elephants, mastodons, until 13,000 years ago. The pods are presently
The Latin species epithet of honey locust, ‘triacanthos’ means
three-parted thorns. Young thorns may be three-parted, but they
can develop into huge branched thorn complexes (below). Safer
thornless types (var. inermis) dominate in plantings and yards.
grown as forage for stock and the unripe pods can be consumed by people as well, as
long as they are not confused with toxic pods of black locust, Robinia pseudoacacia,
or Kentucky coffee tree, Gymnocladus dioicus.
The pods were used medicinally in the Cherokee nation to treat dysentery and measles,
though in Creek villages, boiled branches were tried against smallpox and measles.
Several indigenous communities made cough medicine from the bark and roots.