Ask Mr. Smarty Plants

It is almost always a good idea to deadhead flowers to encourage reblooming, whether they are perennial or annual. The Ratibida columnifera (upright prairie coneflower) is a perennial, but the best way to reproduce it is by seed. The first order of business for any organism is to reproduce itself; in the case of a plant it usually does so by producing seeds. The seeds are a result of the blooming of the plant, which blooms may attract propagators like bees or birds, and then the seeds are produced. Seed production follows along as the bloom begins to dry. If the  bloom is snipped off, usually down to the next twig joint, the plant's plans to reproduced itself will have been thwarted, and it will start up some more buds and blooms, at least until the season is over and/or the plant is exhausted. The blooming period of the Mexican hat is from May to October, with variations allowing for the difference in climate in the 36 states and 4 Canadian provinces in which this plant grows. If you have blooms on your plants now, in early July, you can begin snipping off the fading blooms before they set seed. Most plants do seem to have spurts, or what you refer to as a second flush, of blooms, so you may think you have lost any further blooming when you deadhead like that. However, in a matter of a week or so, new buds will begin to form, and you can go through the whole cycle again. Of course, if you want the plant to self-seed itself, you should leave some of the drying blooms alone, and either harvest the seed or let it fall in place, for more fresh plants next year. Please note that plants that you are encouraging to re-bloom and thus re-seed will need a little extra water as that is going on-you are basically asking the plant to go above and beyond its usual procedure.

Propagation

Propagation Material: Seeds
Description: Very easy to propagate from seed in spring or fall though a fall seeding is recommended. Seeds do not have to be treated but may benefit from a period of stratification. Plants from seed usually bloom the second year. Be sure the seed is in good contact with the soil by lightly raking it into loose topsoil. Seeding rate is two to four pounds per acre. There are approximately 1,230,000 seeds per pound.
Seed Collection: Seed is available commercially or can be collected in late summer. Collect seed from several plants to increase the spectrum of color. If possible, collect seed from plants with solid yellow ray petals to contrast with plants with reddish-brown ray plants.
Seed Treatment: Stratify at 40 degrees for 9 weeks.
Commercially Avail: yes
Maintenance: Supplemental watering may be required if the winter and spring are unusually dry. Watering in summer often extends the flowering period. After flowering ceases, allow seed to completely mature (let cones become dry and brown) before mowing for reseeding or collecting seed to plant in another area.