Boyce Tankersley serves as director of living plant documentation at the Chicago Botanic Garden. His staff’s responsibilities include maintaining records on all aspects of over 2.7 million plants. These aspects include accuracy of inventories, maps, labels, plant purchase order database while also recording phenology (blooming times), carbon storage (carbon sequestration), soils, Image, DNA and Herbarium vouchers and transferring older media images (slides) into digital files. He serves as an advisor to a number of international botanic gardens and arboreta and is active in American Public Gardens Association and Botanic Gardens Conservation International.
His hobbies include gardening, archeology, anything related to geophytes (bulbs) and science fiction literature. He holds a Bachelor of Science in Horticulture from NMSU, a Master of Science in Floriculture from TAMU, and a Certificate in Gardening from the Royal Horticultural Society.
Want to help monarch butterflies? Be careful when selecting your milkweed. Not all plants that go by the common name of “milkweed” are the food that these butterflies need.
Danaus plexippus (Monarch) egg on the underside of a leaf. Photo by Bfpage [CC BY-SA 4.0], via Wikimedia Commons
Milkweed is both a food source and a host plant on which the monarch butterflies lay their eggs. Monarchs lay their eggs on the underside of the milkweed foliage.
After hatching, the larvae consume the foliage, which is high in cardiac glycosides—a poison that interferes with the heart functioning of vertebrates (animals with a skeleton). Butterflies are insects with an exoskeleton, and so are not affected by the toxin.
Within the Chicago region, the following milkweed species (Asclepias) are native:
Asclepias amplexicaulis is native to our prairies and is suitable for planting in sunny perennial flower gardens. The flowers are described as “eraser pink” in color and are fragrant (honey).
Asclepias exaltata is native to our woodlands and is suitable for planting in partially shaded gardens. The flowers are white and also fragrant.
Asclepias incarnata is native to both prairie and woodlands and can be planted in a variety of garden locations. The flowers are pink and fragrant. Gardeners may also be interested in three cultivars of this species:
‘Cinderella’ has light and medium pink flowers
‘Ice Ballet’ has white flowers
‘Soulmate’ has medium and dark pink flowers
Asclepias tuberosa goes by the common name of Butterfly Weed. It features bright gold and orange flowers—and is fragrant. A native of sunny prairies, it also has cultivars that have been selected for specific colors:
‘Hello Yellow’
‘Western Gold Mix’
‘Gay Butterflies’ (orange, red, yellow)
Asclepias purpurascens has fragrant pinkish-purple flowers and can tolerate both sun and shade locations in the home landscape.
Cultivars may be easier to find in your local garden center or nursery, but specialist nurseries do carry both potted plants as well as seeds.
Asclepias syriaca
Asclepias tuberosa
Download the Chicago Botanic Garden Milkweed Map and take a tour of our native milkweeds.
The Bad Seeds
The bad actors, unfortunately, also go by the common name of milkweed, and are in the same plant family but a different genus: Cynanchum. Three species are reported in the upper Midwest and should not be planted by gardeners. All have fragrant flowers and wind-dispersed seeds:
Cynanchum louiseae goes by the name of Louise’s swallow wort, or milkweed. It is native to southeastern Europe.
Cynanchum louiseae goes by the name of European swallow wort or milkweed. It is native to southern Europe.
Cynanchum vincetoxicum goes by the name of white swallow wort or milkweed. It is native to Europe and Asia.
So, why will monarch larvae die on the wrong milkweed?
Hmmm, perhaps an illustration. Both mango and poison ivy are in the same plant family (Anacardiaceae) and contain similar biologically active compounds. My daughter and I can’t get enough mango in our diet, but both break out in poison ivy rashes if we touch poison ivy plants. The compounds are similar but not exactly the same.
Likewise with the “bad” and “good” milkweeds: Both have fragrant flowers, the flower shapes are similar, the leaf shapes are similar, both have milky sap. But there is an insecticide compound in the “bad” milkweed in addition to the cardiac glycoside.
“Bad” milkweeds evolved in Europe, where there are no native monarch butterflies, but plenty of herbivores, both animal and insect. “Good” milkweeds evolved in North America in conjunction with monarch butterflies.
Monarch caterpillar
Somehow, the monarch larvae are able to ingest and retain cardiac glycosides in their tissues without dying. It is a very unique adaptation between these two species. If other species of butterflies were to lay their eggs on milkweed, the larvae would not survive. Each organism has these sorts of “monarch-like” relationships with other, sometimes drastically different organisms that give them a survival advantage. Monarchs just happen to be a wonderful example of mutualistic relationships.
Learn more:
The Monarch Joint Venture lists a number of national and regional partners; each of them will have information about monarch butterflies. The U.S. Fish and Wildlife Service, which is partnering with the National Wildlife Federation and National Fish and Wildlife Foundation, is also a source for information on milkweed and monarchs. Get free milkweed plants at monarchwatch.org.
The clock was ticking—a little girl was seriously ill—when I got the call for help. A Denver hospital needed living tissue from Thujopsis dolabrata or any of its cultivars within 24 hours to determine if the plant was the cause of the girl’s life-threatening allergic reaction.
Don’t call us first! Call the U.S. Poison Control Center at (800) 222-1222. If you need help identifying a plant to determine if it’s poisonous—and it’s not an emergency—try our Plant Information Service at (847) 835-0972. Please bring in a live plant sample for an accurate identification.
The girl had been flown in from Japan to be treated at the hospital, National Jewish Health. After I got the call, I looked into the hospital, which is known worldwide for treating patients with respiratory, immune, and related disorders. In the girl’s case, the doctors apparently had a list of potential allergens they were testing, including Thujopsis, a rare evergreen shrub that is native to Japan.
A hospital official began the search for the plant with a colleague of mine at the Denver Botanic Gardens. My colleague met the girl’s grandmother, who showed her a picture of the patient’s red and inflamed face. When my colleague couldn’t help, she checked around and found via the Chicago Botanic Garden’s free smartphone app, GardenGuide, that we have the plant, commonly known as hiba arborvitae.
While the call came out of the blue—in my 17 years at the Garden, I’ve never fielded such a request—this type of emergency was not new to me. I used to be in charge of landscaping at the University of Texas Medical Branch in Galveston, and occasionally supplied plant samples from the campus gardens to the Texas Poison Control Center. Now, as the Garden’s director of living plant documentation, the response just kicked in.
In the Garden’s production nursery, I snipped a branch from two different cultivars of Thujopsis. Within three hours of receiving the request, I had dropped the samples off at FedEx on the way home.
As it turned out, Thujopsis did appear to be the culprit, and the hospital is continuing to test the girl’s blood samples with extracts from the Thujopsis to determine what constituents are causing the allergic reaction (the same constituents can be found in related species, so the search to identify other potential sources is prudent). Meanwhile, the girl responded quickly to emergency treatment, was stabilized, and returned to Japan.
While public gardens and other outdoor spaces are often recognized for their mental health benefits, this incident reminded me of the fact that botanic gardens have made important contributions to the physical well-being of people in need.
For more than 450 years, botanic gardens have collected and housed plants from throughout the world for the public good, from medicinal plants in the sixteenth century to food crops used to expand and improve people’s diets (like potatoes, tomatoes, and corn introduced to Europe from the New World, and global economic plants like tea and cocoa). I’m proud to be a part of this history.
Each fall, we sing the praises of fall allium and autumn crocus blooms. This year, however, a special mention must be made for the glorious gladiolus! Especially the delicate, 4-inch salmon pink flowers of the salmon gladiolus (Gladiolus oppositiflorus spp. salmoneus).
Hailing from the summer rainfall areas of the cold, higher elevations of the Drakensberg Mountains of South Africa, this beautiful wild species has proven amazingly hardy in the Chicago Botanic Garden’s Graham Bulb Garden over the last five years—including a couple of winters with record-setting cold temperatures!
Gladiolus oppositiflorus ssp. salmoneus produces elegant, upright flower stalks that do not require staking!
Two characteristics of its native habitat nominated the gladiolus for trial at the Garden: first, it is a winter-growing bulb in South Africa, which translates to summer growth in North America. Second, this plant thrives in moist soils in grassy areas—it was perfect for the site we chose in the Bulb Garden.
Based upon its initial success in our plant trial program, other gladiolus (also currently in full flower) were added to the trials. We’ve also discovered that these wild species thrive and multiply in well-drained soils (but do not tolerate flooded soils). The beautiful, red-flowered Gladiolus saundersii is also native to the Drakensbergs, but from a higher, colder, and snowier habitat. And a third selection is probably a close relative of Gladiolus dalenii var. primulinus. Discovered in an old, abandoned farmstead in North Carolina, and sold under the name ‘Carolina Primrose’, this gladiolus generally blooms in July and early August (although it is still blooming now). All have come through the record-breaking cold of the last couple of winters.
Gladiolus is the largest genus in the Iridaceae (iris plant family) with 255 species worldwide; 166 of them in southern Africa. The genus was given its name by Pliny the Elder, in reference to the size and shape of the leaves, which are similar in shape and size to a short sword favored by Roman-era gladiators: the gladius.
It’s not easy to find commercial sources for these bulbs, but it’s well worth the effort to obtain an elegant, refined, fall-flowering, and hardy gladiolus.
