The Mt. Cuba Center has just published Helenium for the Mid-Atlantic Region, a 16-page report detailing the results of a 3-year trial of 44 taxa of Helenium plants. A member of the Aster family, the genus Helenium has summer to fall-blooming perennials with daisy-like flowers about 2 inches across. The flowers are in various colors of yellow, orange, and red, with raised yellow to brown centers, making them look like buttons.
The flowers are beautiful, but the plants are not commonly found in American gardens. Part of this may be because its common name “sneezeweed” leads people to erroneously assume the flowers cause allergies. In fact, the flowers are pollinated by insects, not wind. Sneezeweed is finely ground plant parts that are inhaled, like tobacco snuff. Part of the unpopularity may also be the plant’s tendency to flop over, exhibit powdery mildew, and/or contract a disease called aster yellows. Although they require full to partial sun, they are not drought tolerant and native plants are found growing in wet areas.
When asked why this genus was chosen for the trial garden, Sam Hoadley, Mt. Cuba Center’s Horticultural Research Manager, answered: “Helenium really is a genus that is native to the Americas, and there are several species native to the eastern United States. They are really not well represented in American horticulture. I think, outside of the native plant communities that will work with Helenium autumnale and Helenium flexuosum, we felt that this [trial] represents a fairly diverse group of plants and deserves a second look in American horticulture after it’s been so popular in Europe to see how these plants perform there. We also knew that they have significant benefits for bees and wasps, anecdotally. We really wanted to see how these plants would perform and what benefits or attraction they would have for these pollinators when brought back to the United States.”
Heleniums are popular in European gardens where extensive breeding has been done in Germany and the Netherlands. German breeders Karl Foerster, Gustav Deutschmann, Peter zur Linden and Dutch breeders Inez Arnold and Bonne Ruys have cultivated many Heleniums for exquisite flower colors, shorter forms, and increased resistance to drought. Karl Foerster in particular created more than 70 cultivars drawing on two native American species: H. bigelovii, which is found in Southern Oregon, California, and Arizona; and H. autumnale, which is found across the country. These plus a third species that is found in the eastern United States, H. flexuosum, were included in the trial.
“They really contribute some great late-season interest,” said Sam. “They are in bloom when gardens are in a lull, right at the end of summer and the beginning of fall, bridging a gap in the garden. There’s been a lot of Helenium breeding so that size, stature, and habit of the plant are becoming more and more diverse. For that reason, you are able to incorporate it into more garden designs.”
In the trial at the Mt. Cuba Center in Delaware, forty-four taxa including three species were grown in full sun on clay-loam soil. By the beginning of the third or final year, only one-third of the original 220 plants remained. Plants were given minimal care although staff did try to prevent the flop with the Chelsea Chop and several staking methods on some plants to see which would work. Plants were watered during the first year for establishment and during any extremely dry periods. They were not sprayed with fungicides. Many plants succumbed to dry soil, powdery mildew, aster yellows, and possibly poor winter hardiness.
The downloadable report has three tables: performance summary ratings and plants characteristics, plants that did not complete the trial, and best Heleniums for bees and wasps. Plants are rated on a scale of five (excellent) to 1 (very poor) and include a variety of criteria. None received a five but the top rated, Kanaria, is 4.3, followed by Flammenspiel and Zimbelstern at 4.2, Can Can at 4.1, H. flexuosum at 4.0, and H. autumnale at 3.9. The Mt. Cuba Center’s Pollinator Watch Team observed the plants and found that bees and wasps preferred H. autumnale followed by Zimbelstern, Kanaria, Can Can, and Tijuana Brass.
Since 2002, the Mt. Cuba Center trial garden has been evaluating native plants and their related cultivars for their horticultural and ecological value. See their website for past reports on phlox, monarda, baptisia, coreopsis, heuchera, echinacea, and asters.
All photos courtesy of Mt. Cuba Center.