Gardening with Gary

Gardening Advice from an Expert

Coneflowers

Q. We purchased our first coneflower to see if we would like to grow more. The flowers are fading and dropping their petals and we are not sure if we should have cut them off when they first started to encourage new flowers. How do we encourage new flowers? How do we propagate them? How much longer should we expect them to produce new flowers? Sorry to ask so many questions, but not much information is given when you buy them, even from the nursery.

A. This is a fine plant for gardening, once you learn a few requirements that it has. Here is a synopsis for you:

Rudbeckia, Coneflower, Rudbeckia speciosa
Relative of the Black-eyed Susan and same culture.

They require full sun; do not tolerate shade. Any good well-kept garden soil fits them well. Yearly additions of organic matter help develop a good loam. Where a poor soil is to be planted for the first time, it should be amended by mixing at least one-third organic matter, one-third sand, and one-third soil by volume.

It must be well-drained. Periods of standing water on the soil are damaging to perennials both in summer and winter. In heavy soils, add liberal amounts of sand and organic matter to ensure good internal soil drainage. If external drainage is poor, consider raised beds.

Blooming season is July and August. Keep old fading flowers [and those dropping their petals] cut off to prevent the plants from seeding, which will shorten the flowering and send them toward dormancy. Cut entire flower stems right back to the main growing part.

Maintain a good fertilizer program from spring to fall, heaviest during the flowering period. Use a formula high in Phosphorus or a Bloom Booster, every two weeks.