ARBORETUM JOURNAL

Chestnuts and Horse Chestnuts

In the large brick planter on the patio of Laxson Auditorium is a small deciduous tree now festooned with candelabra-like arrays of many bright scarlet flowers with yellow centers. This is the red horse chestnut #198 Aesculus x carnea on the Campus Trees map. With its pleasing dark green foliage, rounded shape, and small size, it would make a fine choice for the small yard or lawn; however, like many trees, it does drop twigs, leaves, and fruits in the fall. Like all horse chestnuts and their cousins the buckeyes, the nuts are poisonous and must not be eaten! In fact, they contain a deadly alkaloid called aesculin, which stops chromosomes from dividing but is useful as a medicine for horses, hence the name “horse” chestnut. Since the nuts are very bitter, no person would normally eat enough to become sick.

The “x” in the botanical name of the red horse chestnut indicates it is a garden hybrid and cannot be found in the wild. One of its parents is the common horse chestnut (#64 Aesculus hippocastanum), a popular streetside and garden tree in Europe and the eastern United States. We have a large specimen in the lawn behind Kendall Hall; it’s the tree with a painted gnome looking out from a cavity in the trunk. Fifty years ago, a branch split off, creating the cavity, and an attempt was made to patch it with concrete. Then, in the early sixties, a student added the artwork. Now, we wouldn’t think of placing concrete, or any material for that matter, over a tree wound, for we know it encourages rot and destroys the tree, as you see happening here. In preparation for the eventual loss of this tree, we have planted one of its offspring beside it.

There are many California buckeyes in the Sierra foothills, with large palmately compound leaves identical to the horse chestnuts but with even larger fruits. You can see several of these shrubs (#149 Aesculus californica) on campus on the north side of Holt Hall and the west side of Meriam Library. They have cylindrical spires of many white flowers, much like the common horse chestnut. I have enjoyed the spectacular spring floral display of one in my backyard for almost 50 years. It requires no watering and is now about 12 feet high. The early pioneers derisively called it “California pear” for its large fruits. The local Indians often ground up the poisonous nuts to poison fish or leached out the aesculin poison from cooked nuts (by running water over them for several days) and made a surprisingly palatable mush from them.

The edible chestnuts are closely related to oaks and are different in many ways from the horse chestnuts; most important, their nuts are sweet and delicious. Chestnut flowers lack petals, and the males are in the form of a long catkins separate from the inconspicuous females. Also, the fruits are very spiny. We have several old American chestnuts (#165 Castanea dentata) along the road in front of Holt Hall as well as a number of their handsome offspring along the nature trail in front of Holt Hall. These are all that remain of many planted by Bid-well along Sowilleno Drive in 1870. A diary entry of Bidwell in 1880 relates that he and Annie harvested the first nuts from them that fall. They are still producing, and you will see many people eagerly harvesting the delicious nuts each October—that is, if they can beat the squirrels to them!

Wes Dempsey