Jenny Heringer Vires, Robert Geneve, and Robert Anderson, Department of Horticulture
There are nine species of coneflower (Echinacea), all native to central or eastern North America. Only purple coneflower (Echinacea purpurea) is extensively cultivated in nurseries. Coneflowers are hardy herbaceous perennials in the Asteraceae family. They produce large, terminal composite flowers with an outer ring of showy ray florets. These florets can be various shades of purple, white, or yellow. The numerous, inner central disk florets form the characteristic "cone" for this genus and are subtended with a stiff bract that is usually pigmented yellow and provides an interesting contrast with the showy ray florets. Plants bloom over a long period in the summer. Purple coneflower has been used in formal and informal perennial plantings and is the mainstay of naturalized prairie wildflower mixtures. It is also effective as a cut flower.
Coneflowers are also the main ingredient in the medicinal herb preparation sold as Echinacea. It is currently the top-selling over-the-counter herb supplement in a multimillion dollar industry. Echinacea is touted for its immunostimulatory and antibacterial properties. Although all parts of the plant contain the pharmaceutical compounds, the dried root has the most commercial value for drug extraction.
The objective of this study was to evaluate the cultural requirements for production of coneflower species under field conditions in Kentucky either for nursery production or drug extraction. The species evaluated in this study are listed in Table 1.
Seeds for all species were stratified between two and eight weeks prior to sowing in plug flats under standard greenhouse conditions. Eight-week-old seedlings were transplanted to the field in raised beds with drip irrigation in May. Plants were spaced 8 inches apart on center with two rows of plants per raised bed. Each raised bed was on a 2-foot spacing to facilitate mechanical weeding between beds. Weeds were removed by hand from raised beds. Plants received approximately 1 inch of water per week. Plants were harvested in October and evaluated for biomass production.
Treatments included fertilizer application and flower bud removal and were applied only to the Echinacea purpurea open pollinated and Echinacea purpurea cv. Magnus. For the fertilizer treatment, half the plants were fertilized once in May with 20-20-20 Peter's soluble fertilizer through the irrigation line, while the other plants were fertilized twice with the second application in July at the same fertigation rate. Within each of these fertilization groups, plants either were allowed to flower normally or the flower buds were removed as they appeared once a week.
All species and cultivars evaluated in this study produced plants of acceptable size and commercial quality except Echinacea angustifolia (Table 1). This species did not establish as robustly as the other species and experienced the greatest mortality. In this group, two species currently not widely available in the nursery trade stood out for their unique horticultural qualities. These were Echinacea tennesseenis and Echinacea paradoxa.
Echinacea tennesseenis produced more flowers than any of the other species tested. They were similar in size, color (more mauve than purple), and shape to flowers in purple coneflower (Echinacea purpurea), but they were produced on long, wiry stems that appear to be heliotropic (following the sun). The vegetative portion of the plants were also more spreading and low growing compared to the other species in this trial, but in-flower plants reached a height of 3 feet. We feel that this plant has enormous commercial potential for the herbaceous perennial market. Not only does it have numerous ornamental qualities as a garden and cut flower plant, but it is also a Kentucky native plant that is on the Federal Endangered Species list, which should add to the marketability of this species.
Echinacea paradoxa is the most unusual member of this genus. It is the only Echinacea with yellow flowers. It is the least recognizable of the coneflowers and is not usually listed in even comprehensive herbaceous perennial references. It produces a clear yellow flower on strong, erect plants that reaches between 2.5 and 3 feet tall. Its market appeal should be in the unique color, flowering time, and strong growth habit that separate it from other coneflowers and near relatives like Rudbeckia.
All Echinacea purpureal cultivars produced commercially acceptable plants. `White Swan,' a white flowering purple coneflower, was the smallest cultivar, while `Clio' and open pollinated derived plants had the highest biomass. By preventing plants from flowering, there was a significant increase in root biomass. Plants responded to the first fertilization, but there was no significant increase in biomass associated with the second fertilizer application.
Several species of Echinacea not usually found in production nurseries were evaluated for growth under field conditions. Two (Echinacea tennesseenis and Echinacea paradoxa) have potential for mass production. These plants have unique horticultural characteristics not found in the commonly cultivated purple coneflower (Echinacea purpurea) and could be used to exploit a market niche for nurseries interested in new plants native to North America.
| Table 1. Root biomass in field-grown Echinacea species after one season. | |
| Coneflower Species |
Overall Plant Dry Weight (grams/plant) |
| Echinacea purpurea (open pollinated) | 124.3 |
| E. purpurea cv. Bravado | 115.6 |
| E. purpurea cv. Bright Star | 122.5 |
| E. purpurea cv. Clio | 122.4 |
| E. purpurea cv. Magnus | 115.6 |
| E. purpurea cv. White Swan | 87.5 |
| Echinacea angustifolia | 26.6 |
| Echinacea pallida | 79.1 |
| Echinacea paradoxa | 65.5 |
| Echinacea tennesseensis | 120.0 |
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