How To Grow Disease-Free Roses

Many gardeners unnecessarily fear growing their favorite flower. Yes, roses do have a reputation for being disease-prone, but it’s often more the gardener’s fault when the poor posies come down with the horticultural sniffles. Here’s how to keep black spot, mildew and other rose diseases at bay.

  1. Plant to Prevent! Always locate roses in open, un-crowded areas where the plants will get lots of airflow. That means not right up against a house or other structure, and not in an area where shrubs are blocking the flow of air through the landscape.

  2. Morning Sun is #1! Roses MUST be positioned where they will receive the very first rays of the morning sun. A little afternoon shade is fine—and even preferred as we move into hotter regions, but the plants must get that early sun to dry off the morning dew as soon as possible. Roses that have to wait until 11am or noon to dry off will never be healthy.
  3. NEVER prune in the Fall. Fall pruning is dead wrong for all plants. In the Fall, plants begin to go dormant, sending all of their energy down ‘to sleep’ in their roots. Pruning stimulates new growth, thus forcing the plants to grow in the opposite direction of what Nature is telling them. Fall pruning always stresses and weakens plants, and can outright kill them if a sudden cold snap freezes all that succulent new growth.
  4. ALWAYS prune in the Spring. Although you can safely prune your roses in the dead of winter (“dormant pruning”), I prefer to wait until the first new growth appears in the Spring, when the difference between healthy and unhealthy growth is more obvious. When that new growth appears, prune off the tips of all your canes, and, of course, remove any dead, damaged or visibly diseased parts. You don’t need to clean your pruners with bleach or other dangerous stuff; just cut well past the damaged or diseased areas, into healthy new growth. Its better for the rose and your pruners will never get contaminated.
  5. Get Rid of Last Year’s Spores. After you finish pruning, clean up all your cuttings and remove and discard all the old mulch underneath your roses; it’s filled with disease spores just waiting for warm weather. This is the single most important thing you can do to prevent disease.
  6. Then Mulch Against Disease. NEVER use shredded bark, wood chips, ‘colored’ mulches or rubber mulch. With roses, you want an inch of high-quality compost covering the soil. Begin this mulch a few inches away from the base of the plants and go out as far out as the furthest canes will reach that season. The compost will prevent weeds just as well as those other (often highly problematic) mulches, and conveys a dramatic extra benefit: The living creatures in that compost will fight disease three different ways. They’ll make the surface of the soil less habitable for disease, compete with the disease organisms for food, and actually EAT many of the spores that blow in—before they can breed.
  7. Re-mulch mid-summer. About halfway through the season, remove the compost mulch under your roses and replace it with a fresh inch to keep the disease prevention power at its peak. You can use that compost around other (non-disease prone) plants if you wish. If you have had persistent problems with disease in the past and/or live in a very humid climate, replace that compost monthly.
  8. Prune throughout the summer to keep the plants open and uncrowded. Airflow is critical. As with fruit trees, you want to keep the centers of your plants open so that air can circulate through them and create an inhospitable environment for disease. Don’t be afraid to reach all the way down and take out a few canes at the base. And always cut on an angle; rain will pool up on a flat cut.
  9. Water wisely! You can’t prevent Nature from wetting the leaves of your roses, but you can prevent you from doing it. Always water roses at the base; never wet their leaves. Water in the morning, never in the evening or the heat of the day. And make it a deep watering, not frequent, shallow sprinkles. Rose roots MUST dry out between waterings or they will rot. Don’t water if rain is abundant, and try and a wait a week in between waterings.
  10. Naturally disease-resistant varieties? Legendary rosarian Dr. Tommy Cairns says that the older the rose, the more likely it will be disease-resistant; that roses with waxy leaves will always be more disease-resistant than roses with papery leaves; and oddly, the lower growing the rose, the more resistant it should be.


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