Chilopsis linearis. DESERT WILLOW. Southwestern United States, Mexico
BIGNONIACEAE (Bignonia family)

A small deciduous tree with hanging, sharp-pointed seed pods about 10 inches long by 1/4 inch diameter, with two short bracts. As with catalpa, the pod splits to reveal a stiff divider about 1/8 inch wide. The very narrow leaves are 3 to 4 inches long by less than 1/4 inch wide. There are well over 50 of the tiny kernels, which are only about 1/8 inch long and concealed in a hair-fringed shell about an inch long. The kernels can be located by crushing on paper which, when held up to the light, will reveal a tiny oil spot. The attractive flowers, resembling those of both the catalpa and jacaranda, hang as 1-1/2-inch-long trumpets. One of the five wavy-edged lobes of the trumpet appears to be designed as an insect landing strip. The four hard-to-find anthers are tucked away inside.

See several street trees on Campus Drive East to the west of the entrance to SAE house. The dissection of a desert willow pod would be fun for school children and could lead to a discussion of the hairiness (in-pod insulation? or aid in dispersal by wind? or something else?); the canoe shape (slows the fall? or makes a protective tent for a fallen kernel?); why is the pod so long and why does it hang on the tree for so long (for protection against some pest? or for slow release of seeds to guard against infrequent showers of rain in the desert?); what is the function of the divider (stiffen the 8-inch-long pod? or is it merely a relic of a primitive two-celled ovary from times before the pod evolved to today's extreme length?). Such class discussion following a field trip would promote environmental awareness and also exemplify Galileo's theme that knowledge can be obtained directly from nature by experiment as well as from people.

Illustration: McMinn, Howard E. and Evelyn Maino. 1951. An illustrated manual of Pacific coast trees; with lists of trees recommended for various uses on the Pacific coast by H. W. Shepherd. 2d ed. Berkeley, Calif.: University of California Press.

Illustrations (links open new windows): flower | Silhouettes from Trees of Stanford & its Environs

Additions/Revisions: 3 trees back of Children’s Center, west corner, 685 Pampas Lane.

Name derivation, genus | species from Greek cheilos (lip) and opsis (resembling), referring to the corolla of the showy flower | linearis--lined (the purple lines in the flower throats)

Related material: treatment in Jepson Manual |

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