Unfortunately, there are no modern hybrid roses which can be considered drought tolerant
or heat tolerant. That said, there are some techniques you can employ during our hot
summers to reduce the watering needs of modern roses, thus reducing the heat stress they
undergo.
Reduce the fertilization schedule on your roses as they enter the summer months. This
reduces their bloom schedule and reduces the amount of new growth put on during the heat
of summer. Depending on which type of fertilizer you use, this means reducing the amount
of fertilizer from two weeks to 30 days prior to when we expect our hot weather to sustain
temperatures near 98F. For North Texans, we can expect these temperatures by mid-June.
That should be your signal to start reducing your fertilizing until late in the summer.
I prefer organic fertilizers, and fertilize heavily in late-February, then monthly until
mid-May. I stop fertilizing until late-August.
Consider using lighter-colored roses. Red, orange and lavender roses show heat stress more
quickly than white, light-pink and pale yellow roses.
When watering, apply deeply. Deep watering roses ensures moisture will penetrate down into
the root zone where micorrhizal fungi and the root "hairs" maximize the surface area of the
roots and provide the most efficient use of the water. Remember, too, that the root zone
extends well down and away from the "drip line" of the rose. And if using roses grafted onto
Fortuniana rootstocks, those roots will be closer to the soil's surface.
To retain the moisture and moderate soil temperatures, ensure you have mulched heavily with
3 - 4 in. of shredded hardwood mulch.
Apply antitranspirants. These waxy polymers help reduce the transpiration of moisture through
leaves and stems. Products like Cloud Cover® or Wilt Pruf® or similar antidesiccants, sprayed
per label directions, will help reduce the heat stress experienced by the rose.
Replant your more heat-susceptible roses to the east side of your home or where they will receive
protection from the hot, afternoon sun. When doing this, be certain they will still receive a
minimum of 6 hours of direct sunlight. But that sun should be "morning" sun.
Consider changing out some of your roses to those more tolerant of our southern heat extremes.
Many of the so-called "antique" roses are more adapted to our heat and weather excesses here in
Texas. These would include the Teas, Chinas, Hybrid Musks, Hybrid Perpetuals, Bourbons and many
more Classes. Avoid using antique roses bred for colder climates such as the Kordes Roses and
Rugosas.
By Mark Whitelaw, Kindly Provided by Laura Whitelaw
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