Encyclopedia of Stanford Trees, Shrubs, and Vines

Gleditsia triacanthos. HONEY LOCUST. Mississippi Valley
LEGUMINOSAE (Pea family)

A deciduous tree whose compound leaves appear in March. A distinctive feature is the large, flat, pointed pod, around a foot long and an inch wide, containing sweet pulp and many shiny brown oval seeds 3/8 inch long. The pods are edible when fresh; some continue to hang on after the leaves fall. A group of two stands with the two male carob trees in the northeast corner of Galvez Street and Memorial Way. Wicked spines, some with stout side spurs in threes can be seen on the branches. So extraordinary are the larger and more complex of these armaments that it makes you wonder what the tree had in mind to guard against. The wood is durable in the ground, hard, strong, and suitable for craft work. A spineless variety may be seen at Florence Moore Hall. Others are growing inside the front, fenced area of the Children's Center on Pampas Lane. The national champion honey locust is in Chambersburg, Pennsylvania, and was 120 feet high in 1967.

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The Pea family is among the largest flowering plant families with about 18,000 species in 630 genera worldwide. Caesalpina is the type genus for the Fabaceae subfamily Caesalpinioideae, following Cronquist (1981). This subfamily is intermediate in flower morphology between the other two higher-level classifications Mimosoideae and Faboideae (or Papilionoideae). The latter and largest group includes plants with papilionaceous, "butterfly-like", corollas (with standard, wings, and keel)—as the common garden pea.

All subfamilies are well represented on campus for closer study. Caesalpinioideae and Mimosoideae include mainly tropical trees with pinnately or bipinnately compound, alternate leaves. Mimosoideae flowers are regular (radially symmetrical), the corolla with equal petals often fused into a tube. Campus representatives include Acacia, Albizia, and Gymnocladus. Caesalpinioideae flowers are usually more or less zygomorphic (divisible into equal halves in one plane only). As with Caesalpina spp., the petals are distinct, the uppermost often smaller than the laterals. Other campus members of the subfamily include Bauhinia, Cassia, Cercis, Gleditsia, and Parkinsonia. It would be instructive to work out the higher classification of the many other campus peas (genera listed in the family index) from field observation throughout the year.

— further reading: Wendy Zomlefer, Guide to Flowering Plant Families, Univ. of North Carolina Press, 1994.

Name derivation, genus | species After Johann Gottlieb Gleditsch, Director of the Botanical Garden at Berlin,1714-1786 | Greek tri (three) and acanthos (spine), with three spines.

Related material: Canopy Trees for Palo Alto Tree Library

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