Hoptree - Ptelea trifoliata
Other common names for this plant include Swamp Dogwood, Waferash, Shrubby Trefoil, and Stinking Prairie-Bush.
Importance as a caterpillar food source: Giant Swallowtail use the leaves of hoptree as caterpillar food. While Giant Swallowtail will use other plants in the same plant family as hoptree (the citrus family know as Rutaceae), few of the other native citrus family plants have such a northern and widespread growing range.
Importance as a butterfly nectar source: Hoptree produces nectar that is attractive to many butterflies and pollinators.
The following article originally appeared in Butterfly Gardener (Vol. 13, Issue 4, Winter 2008). NABA member Lenora Larson has graciously allowed us to reprint it here.
Host Plant—Hoptree
By Lenora Larson
Family reunions often gather an astonishing variety of relatives: many sizes, shapes and lifestyles. Plant families share this diversity. Who would ever guess that Common Rue, Orange Trees, Prickly Ash and Hoptree belong to the same family, Rutaceae? The Giant Swallowtail Butterfly knows. She lays her eggs on all members of the Rue family and no other. 
Citrus growers despise the caterpillar, the “Sun Dog” and relentlessly spray pesticides. Mimicking a bird dropping may fool other predators, but gains no mercy from humans.
Butterfly Gardeners who live in tropical climates will gladly share a few leaves from Orange and Lemon Trees with Sun Dogs, knowing what they will become. The magnificent black and yellow Heraclides cresphontes is the largest butterfly in North America with a wing spread up to 6”.
We more temperate gardeners must look to hardier hosts. Common Rue, Ruta graveolens is a garden-worthy choice from zones 4 to 9 and also hosts caterpillars of the Eastern Black Swallowtail. But many of us prefer native plants. Prickly Ash, Zanthoxylum americanum, grows from zone 3 to the Mason-Dixon line and west to Nebraska. This native adapts to almost any soil and sun situation, but its thorns are daunting and habits scraggly. The fastidious gardener might better choose the Hoptree, Ptelia trifoliata. Brewmeisters would agree since its fruit is a substitute for hops in beer-making.
This small, multi-stemmed tree has glossy, dark-green leaves that exude a citrus smell when crushed. Hardy from zones 3 through 9, it grows to 10 feet in light to deep shade, which makes it an ideal understory tree. The slow-growing Hoptree does not overpower a small urban garden and will happily adapt to containers for an apartment dweller’s patio or balcony. My attempt to prune one into a standard was a dismal failure. It flopped and flailed until I took pity and cut it to the ground so it could re-grow as a multi-stemmed large shrub.
Like many natives, Hoptrees are an easy maintenance choice. I’ve yet to find scattered seedlings or diseased leaves. Chewed leaves are celebrated because they signal the presence of Sun Dogs. Soil can be clay, loam, or sand, both acidic and alkaline pH. And while it prefers moist conditions, Hoptrees are drought resistant once established.
The pale greenish flowers are borne in terminal corymbs, 2" to 3" in diameter. You’ll know when they bloom in June because the orange blossom fragrance wafts through the air. Hoptree’s other common name, Wafer-Ash, describes the attractive ½” inch membranous flat fruit. These persistent papery wafers dangle from the branches until they are eaten by birds and squirrels.
In fall, the Hoptree shines again with rich golden leaves. Many nurseries promoting native plants now carry the Hoptree and it easily transplants to become a member of your garden family.
Lenora Larson gardens and hosts butterflies in the cruel winds and clay soil of Eastern Kansas.
| USDA Hardiness Zone | to zone 3 |
| Bloom Period | Early summer |
| Bloom Color | Greenish-white |
| Plant Height | large shrub to small tree: 6 - 20 feet |
| Plant Spread | Dense rounded crown, frequently multistemmed or suckering |
| Light Exposure | Full sun to partial shade |
| Soil Moisture | Well drained |
| Animal/Pest Problems | None |
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Native Range for Hoptree (Ptelea trifoliata)