(The awesome Hackberry Emperor, Asterocampa celtis)
We don’t often think of trees when considering planning a butterfly garden, which is to overlook their importance as host plants for some caterpillars. Today let’s look at the Common Hackberry, also known as the American Hackberry.
A relative of the Elm tree, hackberry trees are adaptable to a wide range of light and moisture levels. Often planted for its purple-red fruit that attracts a wide variety of birds, hackberry can be used as a native alternative for Chinese and Siberian Elms.
(map of Celtis occidentalis from bonap.org: dark green squares mean the species is present in county and native, light green means species is present and not rare, yellow means species is present but rare, and blue means the species is native, but adventive in state)
Importance as a caterpillar food source: Hackberry trees provide many butterfly species with caterpillar food. Although the activity is usually high above easy viewing levels, some guidelines for caterpillar identification are:
- Tawny Emperor caterpillars eggs are laid in large groups of 200 to 500 on hackberry bark or leaves. The young caterpillars feed in large groups.
- Hackberry Emperor caterpillar eggs are laid in small groups ranging from one to twenty.
- American Snout caterpillar eggs are laid in small groups.
- Caterpillars of the Question Mark butterfly live alone on hackberry leaves.
- Mourning Cloak caterpillars live together in a web while eating hackberry leaves.
Importance as a butterfly nectar source: Hackberry is used as a nectar source but its popularity varies by location.
The following article originally appeared in Butterfly Gardener (Vol. 14, Issue 1, Spring 2009). NABA member Lenora Larson has graciously allowed us to reprint it here.
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.Hackberry fruit 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.Hackberry Bark 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!
Lenora Larson gardens and hosts butterflies in the cruel winds and clay soil of Eastern Kansas.
Common Hackberry Cultural Requirements
USDA Hardiness Zone: 2 to 9
Bloom Period: Not applicable
Bloom Color: Not applicable
Plant Height: 60 to 100 feet
Plant Spread: Rounded crown
Light Exposure: Full sun to partial shade
Soil Moisture: Moist but well drained
Animal/Pest Problems: None