Purple coneflowers are quintessential prairie plants. They are hardy, drought-tolerant, and long-blooming, and they are being cultivated in an ever-widening range of colors. It's hard to find a garden without at least one variety. Coneflowers are a type of echinacea, a native eastern North American genus with about 10 species.
Purple coneflower, or Echinacea purpurea, is by far the most popular variety of coneflower. It has a fibrous root system, rather than the long tap root and woody crown found in other native species, and it is more adaptable to garden conditions and more forgiving of dividing and transplanting.
Coneflower's daisy-like flower is actually made up of several small flowers. The petals are sterile and are there to lure insects toward the many fertile flowers in the central disk or cone. These flowers are rich in nectar and very popular with both bees and butterflies. Hummingbirds also enjoy coneflowers, and birds like finches eat the seeds.
How to Grow Purple Coneflowers
Purple coneflowers grow well just about anywhere in USDA hardiness zones 3 through 9, but in colder climates, you may want to give them a little winter protection their first year. Once established, they are rugged and hardy.
Coneflowers grow well from seed and can be divided to make new plants. They can also be grown from stem cuttings but with less success. They're easily found for sale in garden centers and mail order. The plants start blooming in early summer to midsummer and repeat-bloom through frost. They may take a break after their initial bloom period, but they will quickly set more flower buds.
To get the most blooms and the sturdiest plants, plant purple coneflowers in a spot that gets at least six to eight hours of full sun each day. They will tolerate partial shade, but plants may flop and blooms won't be as prolific.
Coneflowers grown in gardens prefer a neutral soil pH of about 6.5 to 7.0. They can thrive in a variety of soil types, including sandy, rocky, and clay soils. However, they do not like wet or mucky soil. For best results, add a bit of compost when planting to give coneflowers a good start.
Coneflowers are often listed as drought-tolerant, but they will do much better with regular watering. Water them daily just after planting, then transition to an inch of water per week. Second-year and older plants may only need watering during droughts.
Temperature and Humidity
As a native prairie plant, echinacea thrives in hot, dry climates but can handle a range of temperature and humidity fluctuations. They do not do as well in very humid climates or in rainy areas where the soil stays wet.
Although coneflowers thrive best in a soil high in organic matter, too much supplemental fertilizer can cause them to become leggy. Adding compost each spring usually gives them the nutrition they need for healthy foliage and blooms.
You can leave the plants standing through winter to feed the birds. Shearing them back in the spring will result in bushier plants that bloom longer into the season.
Deadheading is the primary maintenance for coneflowers. They are prolific bloomers, and deadheading (removing the dead flowers from living plants) will keep them in bloom all summer. Each flower remains in bloom for several weeks.
Flowers start blooming from the top of the stem. As the initial flower fades, more side shoots and buds will form along the stem. Keep the plants deadheaded, and you'll keep getting more flowers. Deadheading also helps prevent an overabundance of self-seeding from the plant.
Growing From Seeds
Purple coneflowers are relatively easy to grow from seed. If you'd like to save the seed, wait until the cone has fully dried. It will be darker in color and stiff to the touch. The seeds are attached to the sharp spines. Wear gloves, and separate the seeds from the cone. Spread them on a paper plate or screen to dry thoroughly before storing.
The seeds germinate best with some cold stratification. The easiest method is to sow them outdoors in the fall, either in the ground or winter sowing them in milk jugs. If you are going to start seed indoors, simulate the chilling period by planting seeds in damp seed starting mix and placing the sealed container in the refrigerator for 8 to 10 weeks. Then, take them out and plant as you normally would. The seeds need dark to germinate, so plant about 1/4 inch deep and cover with soil. They should germinate within 10 to 14 days. Place under lights an inch or two above the plant when seedling emerge.
Common Pests and Diseases
For the most part, coneflowers have very few problems. As long as the plants are given plenty of room for good air circulation, they should not be bothered by fungal diseases. If you should see mildew or spots on the leaves, simply cut them back and let them fill in on their own. A few pests enjoy coneflowers, so keep an eye out for Japanese beetles, vine weevils, and leafhoppers.
Keep an eye out for aster yellows, a systemic plant disease that causes growth deformities in the flowers. It can affect hundreds of different flowers, not just those in the aster family. There is no known cure and it is spread by sap-sucking insects like leafhoppers, so affected plants should be removed and destroyed as soon as possible, to protect other nearby plants.