Coneflowers are perennials

Margo Nelson,

It's high season for adding plants, caring for old-timers

  • Article by: Deb Brown
  • July 28, 2009 - 1:13 PM

Q Is it too late to plant perennials? I see them on sale at lots of garden centers and I'd really like to plug some holes in my flower beds.

A It's not too late at all. In fact, you should be able to plant perennials into early autumn. Just make sure the plants you choose are in good condition and that you're able to water them regularly so their roots get established.

When you shop, avoid any plants that don't appear healthy and steer clear of plants that have outgrown their containers. (For a quick test, pop the plant out of its pot to check.)

Plant each perennial at the same depth it was in the container, then water it well. Spread at least 2 inches of mulch over the root area, but leave a little space for air circulation around the stem. It's generally best to wait until next spring to fertilize because you don't want to encourage new top-growth late in summer. However, if the foliage looks pale after a week or two, fertilize very lightly.

Rose care

Q I'm new at growing hybrid tea roses. Should I be doing something now to keep them healthy and encourage more blooming?

A Typically, hybrid tea roses bloom heavily in late spring, then continue at a slower pace in summer, only to bloom more heavily again once temperatures begin to drop in fall.

Roses are heavy feeders. They bloom best when planted in a sunny location and fertilized monthly, starting in spring when you uncover them, right through mid-summer. But in our climate it's best to stop fertilizing roses in early August, because you don't want to encourage vigorous growth when the plants should be starting to slow down in preparation for dormancy.

In addition to monthly fertilizing, roses need regular, deep watering throughout the growing season. The hotter, drier and windier the weather, the more important it is to water them thoroughly once or twice a week. Mulch will help conserve moisture, keep their roots cooler and reduce competition from weeds.

Be sure to deadhead any rose blossoms that have faded. There are two schools of thought on how best to deadhead roses. Traditional advice says to remove not just the flower, but the stem holding it, cutting back to just above a five- or seven-leaflet leaf. In theory, the new stem that arises from the tiny bud in the leaf axil will be strong enough to produce another flower. Some experience has shown, however, that you get faster re-bloom simply by removing the spent flower and stem down to the closest leaf rather than worrying about how far back to make your cut.

Deb Brown is a garden writer and former extension horticulturist with the University of Minnesota. To ask her a gardening question, call 612-673-7793 and leave a message. She will answer questions in this column only.

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