Echinacea

Resist deadheading the last flush of flowers and let the cones stand through winter. Cut the dead foliage and stems down any time from fall through early spring, before new growth pushes. The standing seed heads are a winter food source that goldfinches work over, so a tidy fall cleanup costs you the birds for no gain to the plant. Deadheading earlier in the season is a different matter and does push rebloom into fall.

Sow indoors where air temperature holds at 65 to 70 F and cover the seed lightly with potting soil to keep light from inhibiting germination. Purple coneflower germinates in 10 to 20 days and seedlings are ready to move on 20 to 28 days after sowing. Echinacea purpurea germinates readily in 10 to 20 days with no cold pretreatment, so the only thing standing between you and transplants is steady warmth. Plants raised from seed need two or more years to reach mature size, so a clean early start buys you a year.

Established plantings need little. As growth resumes in spring you can apply a slow-release 12-6-6 at about 1 pound per 100 square feet, or skip it entirely on decent soil. A soil test is the only way to know whether you need anything at all. Coneflower is a prairie plant and runs on lean soil. Pushing it with nitrogen buys tall floppy stems that fall over in the first storm, which is why the recommended rate is modest and why doing nothing is a legitimate option.

Every three to four years, lift the crown in spring just as new shoots push through, and split it so that every division carries both a shoot and its own roots. Replant at the depth it was growing before. Coneflower crowns crowd themselves out as they age, and the center thins and flowers less. Dividing in spring at emergence means each piece has a growing shoot to run on and a full season to re-root before winter.

As flowers open, look for deformed lopsided heads, petals that stay green and never color up, brush-like tufts of small shoots growing out of the cone, yellowing between the leaf veins, and stunting. Dig out the whole plant, roots and all, bag it, and put it in the trash. Aster yellows is a phytoplasma spread by the aster leafhopper, and the infection is systemic through the entire plant. Snapping off the ugly flower cures nothing, and every plant you leave standing is a reservoir the next leafhopper feeds on and carries to the rest of the planting.

For medicinal use, cut purple coneflower heads when the flowers are at full bloom, working in the early morning. Get them processed the same day, preferably within four hours of cutting. Dry the material at a moderate 20 to 25 C, roughly 68 to 77 F. The active compounds peak at full bloom and start degrading as soon as the head is cut and warms up, which is why the four hour window and the morning cut both matter. Drying hot drives off the cichoric acid you are trying to keep.

Leave seed-grown plants in the ground three to four years before digging roots. Harvest in autumn after the first frost, lifting with a spade or a root digger. Expect roots about 8 inches deep on E. purpurea. Wash them clean, then dry under low forced heat or in open air at 20 to 25 C. Autumn is when root moisture is lowest and the plant has pulled its reserves down into the root, and the roots simply have not built enough mass or enough active compound before the third year to be worth digging.