The Right Place
Coneflowers do well in full sun or partial shade. In areas where summers get extremely hot, it is best to locate the plants where they get some shade in the afternoon. They can also handle windy conditions. The plants will grow in sandy clay soils, but if possible soil should be rich, moist and slightly acid (pH 6.0 to 6.8).
Careful attention to cultural requirements will assure that your coneflower plants are free from stress. Stress-free plants are less likely to experience problems.
Planting Nursery Stock
Plant container grown plants or seedlings in the early spring. Choose an overcast day, or late afternoon on a sunny day, to protect new plants from the hot sun while they recover from transplant shock. When all danger of frost is past, and the soil has dried out enough to be manageable, dig into the soil down about 12 inches or so, loosening and crumbling the soil and removing rocks, weeds and other debris. Mix in some organic matter such as peat moss or compost, if it is available, to enrich the soil and enable it to hold moisture better.
Remove the young plants from their containers, and gently spread any tangled, cramped roots. Make sure holes are wide and deep enough to accommodate the spread roots. Set each plant in the bare hole so that the top of the soilball is level with the ground. Fill the hole with soil, firming it around the base of the plant, and water generously. Plant coneflowers in groups of three, spaced about 12 inches apart.
While it is possible to create more purple coneflower plants by digging up large clumps and dividing them into several smaller rooted plants, their deep taproots do not take to this very well. The new plants may be bushier and develop fewer flowers. An alternative is to allow existing plants to seed themselves.
Leave some faded flowers on the plant well into fall when their dried centers release seed onto the ground around existing plants. Do not disturb the soil over the winter. Look for new seedlings the following spring and dig and transplant them. Purple coneflowers can be started from commercial seeds indoors in late winter for transplanting in the spring. They will bloom later in the same season.