Albizia julibrissin silk tree

Silk trees in fragrant bloom, Math Corner. George Segal’s “Gay Liberation” sculpture in the background. Sairus Patel, 25 Jun 2017

Pink puffball flowers owe their color to tufts of stamens that fade to white at the base. The white yellows as the flower ages, lending a salmon cast to the floral display. The midvein on each leaflet of the elegant, twice-divided leaves is offset toward one side, almost at the margin, giving it the look of a tiny snap pea. Pods hang from the tree and can be quite ornamental; when dry the seeds can be popped out easily and collected, germinating readily when soaked overnight. The leaflets fold shut at night-time, likely as an adaptation to conserve moisture; on campus, this behavior can sometimes be seen with Acacia dealbata as well. Indeed, silk trees are closely related to acacias.

Landscape architect Thomas Church had about ten planted in the Math Corner courtyard in the Outer Quad around 1968; three remain, tall and limbed up. The dome-shaped crown lends itself particularly to campus settings that can be viewed from above, where the flower color complements the terracotta of our tiled roofs. Replanting is warranted; the flowers of younger specimens are more easily appreciated.

One tree struggles in the western courtyard of Florence Moore Hall. Another stands where the Sonoma Terrace bike path enters Stanford Avenue. The faculty residential area has lost several, but some remain at 940 Cottrell Way and on the driveways of 818–820 Tolman Drive. A burgundy-leaved cultivar, ‘Summer Chocolate’ is at the Meyer-Buck Estate just west of the house (map pin).

The genus is named after a Florentine nobleman (his double-z reduced to one in the process of Latinization) who in 1749 introduced it to cultivation in Tuscany from Constantinople; Borgo degli Albizi, a narrow and ironically treeless street, commemorates his family. Julibrissin is adapted from the Persian for silk flower.

Albizia julibrissin leaf. From Trees of Stanford and Environs, Ronald Bracewell