Caterpillar Food Plant: Hackberry
The following article originally appeared in Butterfly Gardener, a NABA publication for members. It originally appeared in Vol 14: No.1, Spring 2009. NABA member Lenora Larson has graciously allowed us to reprint it here.
Host Plant: Hackberry
By Lenora Larson
Is there a perfect tree? Consider the magnificent Hackberry tree, Celtis occidentalis. Many species of butterflies consider it the perfect caterpillar food plant, including the Question Mark, Mourning Cloak, Hackberry Emperor, Tawny Emperor and the darling American Snout. About every five years, we are blessed with huge eruptions of Hackberry Emperors. Leave your car window open, and fifty will perch on your steering wheel, enjoying its saltiness.
Birds also celebrate Hackberry trees. Winter residents such as yellow-bellied sapsuckers, wild turkeys, and mockingbirds depend on the persistent berries. In fall and again in spring, great flocks of migrating cedar waxwings swoop onto the Hackberry tree to gobble berries while discussing their journey in that distinctive musical twitter. And our beautiful fox squirrels eat both the leaf galls and the fruit. I have personally taste-tested the sweetness of the dark red berries, a thin flesh around a single nutlet.
Landscape designers effusively praise the Hackberry tree and rate it “superior.” Like other members of the elm family, it creates a shady canopy, growing to 60 feet with a 40 to 50 foot spread. This American native’s resistance to pollution makes it the perfect urban tree. From zone 3 to Florida’s zone 9, Hackberries flourish in any type of soil: acidic, alkaline, clay or loamy or sandy. Bring on the flood or the drought, Hackberries thrive. Mature Hackberry trees prefer full sun, but will grow in partial shade.
Garden designers yearn for four-season interest. The May flowers are an insignificant green, but the pale green spring leaves and yellow fall foliage are attractive. Even better, the “geographic” bark provides that scarcity, winter charm. Stomping through the snowy forest, a hiker can easily identify Hackberry trees by the light gray bark arranged in deep, corky furrows that look like mountain ranges.
This beautiful native tree feeds animals, grows under tough conditions and harvests as attractive hardwood for furniture and flooring. How can we even question this tree’s perfection? In a word, berries. Hackberries. They are spread far and wide by birds and have at least a 300% germination rate. (OK. The book says 34%, but it seems like 300%). From June to October, I’m patrolling my gardens for seedlings. If you don’t tug the seedlings out the first year, they resist all but the strongest arm. And by the third year, even Round-up requires multiple applications to eradicate the pesky upstarts.
We were so close to perfection! Is there a solution? Yes, “stooling:” the cutting of trees and shrubs to the ground each winter. Butterflies agree with this strategy because the caterpillars prefer the tender leaves of the newly stooled growth to the tougher leaves of an adult tree. My one huge mature specimen keeps everyone provided with winter food. With sharp eyes and luck, all seedlings are eradicated each spring, except for a lucky few that choose their landing spot well. These are maintained as stooled specimens that don’t bear berries and provide succulent leaves for the caterpillars. Stooled specimens are short-lived and after four or five years, they give up in frustration over not being allowed to achieve their genetic potential. No problem, because I can count on the choice of hundreds of replacements each spring. Perfect!