No-Fuss Knock Out Roses

Q Last year was the first flowering season for my Knock Out roses. Every few weeks, I cut off the old blooms, and that seemed useful in promoting a succession of blossoms all year. Would they have performed as well if I had not done that? What is the pruning regimen for the fall? I hadn't considered cutting them back but noticed a neighbor had done so to hers.

AKnock Out roses aren't fussy about how they are pruned. Nor do you need to remove the fading flowers -- a practice called deadheading -- to keep them flowering, though it will make the bush tidier.

Knock Out roses began as a magenta-pink flowered variety but are now a series of roses in different colors. They are part of a new palette of landscape roses that need a lot less care than the fussier hybrid teas. They don't need the fertilization, water or pesticides required by other roses. As a result, landscape roses have become immensely popular, and in some places they dominate commercial landscapes that rely on low-maintenance plants. Ten years ago, I never could have imagined that roses would become so commonplace.

It's best to renew your Knock Out roses every four or five years by cutting them back to a foot or so. It's a thorny job, but it really does result in nicer foliage and more robust flowering.

I received a hothouse azalea in January of last year that was in full bloom. In the spring I put it outside in a planter, and it bloomed again last summer. It rebloomed in late fall, though some of the leaves turned yellow. How should I care for this plant and what is the feeding schedule?

You have been very successful with your azalea. The yellowing and leaf drop are part of the natural cycle of renewing foliage.

Hothouse azaleas, such as those available in the winter and spring holidays, are developed from subtropical species and could not be counted on to survive Washington winters outdoors.

The key to success with these azaleas is to keep them cool in winter and give them all the sunlight you can while they shelter indoors. If you have a bright room or solarium that you can keep at 60 degrees all winter, they will do nicely. The soil should be allowed to dry slightly between waterings, and they must never sit in water. In winter, they are not in active growth, so you don't need to fertilize them.

Place them outdoors as soon as settled spring weather has arrived, around mid-April, and be ready to cover them or bring them inside if frost threatens. This placement outdoors in early spring will mimic winter in subtropical climates and encourage new flower bud development, which is why yours bloomed last summer.

If you leave it outdoors until early November, it may get enough cool weather to bloom again indoors. While the plant is outside, feed it with a half-strength liquid fertilizer every two weeks. If you are forgetful when it comes to fertilizer, you can simply put some slow-release fertilizer on the soil surface when the plant goes outdoors in the spring.

Scott Aker is a horticulturist at the U.S. National Arboretum.