Sapindaceae (soapberry family) Aesculus

Aesculus × carnea red horse-chestnut

Red horse-chestnut blooms at Littlefield Center as American ash, left, leafs out vigorously. Sairus Patel, 9 May 2023
Aesculus × carnea leaf showing 7 (rather than the more common 5) leaflets and fruit. From An Illustrated Manual of Pacific Coast Trees, Howard E. McMinn & Evelyn Maino

A cross between the common horse-chestnut (A. hippocastanum) and the red buckeye (A. pavia), this tree is striking when in bloom. The deep pink flowers are arranged in panicles, carnea suggesting their flesh color. The unstalked leaflets are five in number (occasionally seven), often wavy, and have rounded sawteeth.

A handsome specimen is on the north side of Littlefield Center, just west of Lasuen Street; nearby find California buckeyes and a red buckeye. In 2006, a group of the cultivar ‘Briotii’ – originating in 1858, with bright scarlet flowers – was planted on the south side of Braun Music Center. Three red horse-chestnuts are at 817 Pine Hill Road. About a dozen grow in the parking lot on the west side of the Stanford Shopping Center, north of Arboretum Road.

In Palo Alto, see large specimens on the 500 block of Chaucer Street – along with a couple of A. hippocastanum – and in and near the children’s playground on the west end of Rinconada Park. Many more are sprinkled along the first few blocks of Everett Avenue.

Name derivation: Aesculus – the Latin name for a kind of oak bearing edible acorns but applied by Linnaeus to this genus; carnea – flesh-colored. From California Plant Names.

About this Entry: The main text of this entry is from the book Trees of Stanford and Environs, by Ronald Bracewell, published 2005. (Erratum: the book’s leaf silhouette is mislabeled: leaflets of A. × carnea are sessile.) John Rawlings added the ‘Briotii’ locations ca. 2006. Family updated from Hippocastanaceae to Sapindaceae (Oct 2017, SP). Remove mention of removed specimens: north of Frost Amphitheater, Roble Gym, and School of Education (the latter specimens replacing English hollies); added locations: Littlefield, Chaucer, Rinconada, Everett; edits; all locations up to date (May 2023, SP).