Summer heat can stress many plants in our landscapes. Most roses struggle during the extreme temperatures of mid-to-late summer, so proper care is important as they enter this stressful time of year. Regular watering, mulching and deadheading, as well as insect, disease and weed control, are the major tasks.
August is a good month to prune once-blooming roses, which bloom heavily in the spring and early summer, then very little or not at all the rest of the year. They will blossom next year on the new growth they have this summer.
Everblooming roses, however, will continue blossoming through the summer. When pruning faded flowers (deadheading), you should cut them back to just above the first five-leaflet leaf. Cuts can be made lower on the stem of more vigorous roses to control their size. The next major pruning should take place in late August.
The intense summer heat can dry out beds surprisingly quickly. Roses planted this year need a regular deep watering whenever we go five to seven days without a good rain of one-half to 1 inch.
Established roses are remarkably drought-tolerant and generally don’t require a great deal of supplemental irrigation. They don’t need to be watered until seven to 10 days after the last good rain. During long dry periods, water roses once or twice a week as needed.
Avoid wetting the foliage, if possible, by using drip irrigation, soaker hoses or an irrigation system that sprays water below the foliage. If you must wet the foliage, irrigate during the morning or when it will dry rapidly to reduce diseases.
Daytime highs in the 90s and nighttime lows in the mid-to-upper 70s lower the vigor of roses. Despite your best efforts at proper care, you will notice the flowers produced in mid-to-late summer often are smaller with less vivid colors, and they seem to fade almost as soon as they open.
Many gardeners think the lower vigor and poor quality mean the roses need more fertilizer. Since heat is the issue, however, roses need less fertilizer in late June, July and early August.
Planting and transplanting
Mid-to-late summer is the absolute worst time to plant or transplant roses. If you need to move a bush, wait until late November.
For roses that are highly susceptible to black spot, a weekly spray program is important through the summer months. Fungicides labeled “to control black spot” must be used regularly. This is not a disease you can treat on an as-needed basis.
Even with persistent efforts, black spot can show up when we get regular afternoon rainfall. Still, spraying will help. To avoid spraying, choose roses that are more tolerant of or resistant to black spot.
Various insects will chew on the foliage, or occasionally on the flower petals, but damage usually is minor. Leafcutting bees chew round pieces about the size of a nickel or dime from the edges of leaves, but damage generally is not bad enough to warrant control.
Keep beds well-mulched to minimize weeds. A pre-emergent herbicide, labeled “for use around ornamentals,” such as Preen or Amaze, also can help.
As the spring and summer bloom season ends, don’t despair. With good summer care, everblooming roses can be even more spectacular in October and November.
The Master Gardener Volunteers of Cobb County (MGVOCC) supports the University of Georgia Cooperative Extension Service and strives to improve the quality of life in our community by delivering research-based horticultural information, educational programs and projects.
– Master Gardener Volunteers of Cobb County is a part of the University of Georgia Extension.