Bring in the Rare Butterflies

Like many of us, I enjoy browsing local nurseries. Often, you can run across a plant, shrub, or tree that you don’t see too often—something less likely to happen at gardening departments in big box stores. For example, about a year ago while browsing I noticed a tree for sale not often found in the garden trade in the Northeast: the Common Hackberry (Celtis occidentalis). I snatched it up immediately and planted it in a sunny place in my back yard. In the wild, this tree is grows in the alkaline soils of forests, near streams and rivers, and regenerating fields. But in your yard or garden it is very accommodating in a variety of soils in part-sun to sunny conditions.

The Common Hackberry sapling I bought last year is putting on lots of new growth. The tree can eventually grow to 50-100 feet. My dog Tucker decided to photo bomb. Photo by Willow Sirch.

Most herbaceous plants, shrubs, and trees take a few years to adjust to their new site, going through what’s generally called “sleep, creep, leap.” That is, they are relatively dormant the first year, start active growth the second, and flower in the third. My hackberry is thriving in its second year and putting on lots of new growth.

Why did I jump at the chance to plant a hackberry? The answer is simple: butterflies! Attracting a variety of birds to your yard with this tree is a plus, but it is the possibility of bringing in some rare butterflies that is the real bonus. There are a few butterfly species whose larvae (caterpillars) feed only on this tree. They include the Hackberry Emperor (Asterocampa celtis), the Tawny Emperor (Asterocampa clyton), and the American Snout (Libytheana carinenta). Although none are common, of these three species the Hackberry Emperor is the most often seen. The American Snout is seen only occasionally because it does not overwinter here, but migrates from the south.

Hackberry Emperor butterflies only lay eggs on Common Hackberry. Adults feed on sap, rotting fruit and animal dung. They are one of the few butterflies that will land on your skin to get salts, as you can see in this photo. Photo by Melissa McMasters from Memphis, TN, United States, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0&gt;, via Wikimedia Commons.
Tawny Emperor butterflies are even less common than Hackberry Emperors in Connecticut. Photo by Andy Reago & Chrissy McClarren, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0&gt;, via Wikimedia Commons.
American Snout butterflies occasionally migrate north to spend summers in Connecticut. Notice in this photo the distinctive, elongated mouthparts which make the butterfly look like it has a “snout.” Photo by John Flannery from Richmond County, North Carolina, USA, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0&gt;, via Wikimedia Commons.

Hackberry trees are members of the elm family (Cannabaceae). In the Midwest this tree is often used as a substitute street tree for the American Elm (Ulmus americana), which has been eliminated in many areas by Dutch elm disease.

The warty, pebbly ridges of Common Hackberry bark are very distinctive. Photo by R. A. Nonenmacher, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0&gt;, via Wikimedia Commons.

The leaves of both American Elm and Common Hackberry are toothed. Elm leaves have a more oval shape and hackberry leaves are more elongated and pointed at the tip. Another way to identify a Common Hackberry tree is by its distinctive bark. The light to dark gray bark has pebbly, warty outgrowths on young trees that develop into corky, projecting long ridges on older trees.

The leaves of Common Hackberry are similar to American Elm but are more elongated and pointed at the tips. Photo by R. A. Nonenmacher, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0&gt;, via Wikimedia Commons.

The common name hackberry is from the Old Icelandic heggr meaning “bird-cherry tree” and ber meaning “berry.” Early colonists confused the hackberry’s fruits with the round, fleshy fruits of the Bird Cherry or Hagberry (Prunus padus), a common Old World tree in the Northern Hemisphere. Both trees attract many types of birds to their fruit.

Hackberry produces an abundant crop of orange-red to dark purple drupes, which are one-seeded fruits. Fleshy parts of the fruit are edible and taste a bit sweet, hence another of its names is Sugarberry. However, there is a related species also called Sugarberry (Celtis laevigata) found in the southeastern United States.

A wide variety of birds are attracted to Common Hackberry fruits. Photo by Gmihail at sr.wikipedia, CC BY-SA 3.0 RS <https://creativecommons.org/licenses/by-sa/3.0/rs/deed.en&gt;, via Wikimedia Commons.

Let’s get back to those rare butterflies. As adults, the Hackberry Emperor and the Tawny Emperor feed on tree sap, carrion, rotting fruit, and animal dung. The American Snout nectars on a variety of plants, including dogbanes (Apocynum spp.), Sweet Pepperbush (Clethra alnifolia), and goldenrods (Solidago spp. and Euthamia spp.).

The two Emperors are often associated with each other. Researchers have found that they display niche partitioning. That is, they don’t compete with each other. Tawny Emperor larvae usually feed on older leaves, whereas Hackberry Emperor larvae feed on younger leaves.

So keep an eye out for this remarkable tree. If you find it and have room in your yard, plant one. Before you know it, you’ll be hosting and enjoying some rare native butterflies.

Published by Jim Sirch

Jim Sirch is the author of Beyond Your Back Door, a weekly blog about nature in your neighborhood. He is also Education Coordinator for the Yale Peabody Museum, a UConn Master Gardener and board member of his local land trust. As a trained naturalist, he brings a deep understanding of geology, plants and wildlife and how they interact within a particular ecosystem. He holds a B.S in Forestry from West Virginia University, a B.S. from Miami University in Science Education; and an M.S. in Environmental Studies Administration from Antioch University. He is also the 2014 Sigmund Abeles Award recipient from the Connecticut Science Teachers and Supervisors Association for outstanding science teaching and professional development.

12 thoughts on “Bring in the Rare Butterflies

  1. I always look forward to reading your blog, and I have learned so much! Thanks, Jim, for sharing your knowledge. And I wish I had space in my yard for a hackberry tree!

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  2. Never heard of this tree; thanks for sharing the info on the butterflies that are attracted to Hackberry.

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    1. Thx Gail – good to know. That doesn’t surprise me that they are on East Rock. They like more neutral soils and the pH is higher there because of the trap rock. They are also found in an the marble valleys in northwester CT. Cheers, Jim

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  3. Thanks again Jim, for a really fun and informative article! I’ve been on the lookout for the butterflies you’ve mentioned here, as they are all beautiful and unusual. Congratulations on your magnificent hackberry tree! Just FYI, if you need a good source for native plants,trees and shrubs, Earthtones Nursery in Woodbury is a good destination. I’ve had luck with them in procuring harder to find natives. They carry species, not cultivars– a plus when planting for wildlife.

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  4. Thanks, That was very interesting. You mentioned the hackberry bark being similar to American Elm bark. I actually have an American Elm in my yard that volunteered just before it’s parent died of Dutch elm disease. It’s doing well…taller than my house and full of squirrels and birds.
    Keep the blogs coming. They’re great!

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    1. Hi Beth, Yes I have really large one in my yard now. I have heard that American elms do fine in some sites, particularly if they get enough water/good soil.

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