Take special care of roses in hot weather

Frank Brines

ARS Master Rosarian

I always enjoy looking back to last year’s care column for the month. According to weathercurrents.com, the hottest Oct. 1 was in 2020 at 102.8 degrees. In 2022, the region got slammed with a high Oct. 19, of 113 degrees. According to the same site, the “normal,” or multi-year average, for October is 82 degrees and the low was 54 degrees.

So, the watchword is “vigilance” – watch the forecast and make sure to adjust your watering program to be neither stingy nor wasteful. Your roses will reward you for it.

On that same note, mid-season pruning and fertilizing should be carefully coordinated with weather conditions. When pruning and grooming your roses at temperatures in the 90-100s, don’t remove so much foliage that the canes are overexposed to the fierce sun because sunburn can damage or kill otherwise healthy canes or entire plants; it is more likely if your plants are water stressed, which is another good reason to keep your watering system in good repair and your watering program in sync with weather conditions.

It takes only a few days of 90 degree temperature for a bush to become seriously stressed and damaged without sufficient water. Hybrid tea roses can survive with 3 gallons of water twice a week. Make that your absolute minimum. The composition of soil affects water retention and the time for the soil to dry out. Four inches of good mulch will reduce evaporation of soil moisture. With potted roses, mulching is even more critical.

Morning is the best time to assess your garden conditions. Look for wilted or dry crispy foliage. If discovered soon enough, dousing severely stressed plants with plenty of water may save it. If you wait until afternoon or evening to inspect, it may be too late. After a hot day, even plants receiving sufficient hydration can appear a little wilted, so afternoon checking would give you wrong information.

Routinely inspect the irrigation system to make sure it is delivering water as designed. Correct any problems ASAP: Your plant’s life depends on it. Plants in clay pots require more water, plants in plastic pots are better. Soil in any type of pot material can pull away from the sides of the pot and water will just run through and out the drain holes in the bottom. This problem can be corrected by pressing the soil back against the inside sides of the pot when the soil is wet.

Saucers under the pots may help too as long as water is not allowed to remain in the saucer for longer than a day.

Spider mites and chili thrips are common problems in hot, dry, dusty conditions. This topic was covered in the September rose care column. Visit https://www.temeculavalleyrosesociety.org. Control is by spraying every seven to 10 days with any product containing Spinosad. I missed spraying this year, and my garden shows it. I started pruning around Sept. 19, which is cutting it pretty close to have something to exhibit at fall rose shows.

Speaking of which, the Orange County Rose Society is sponsoring a show Saturday, Oct. 28, in Yorba Linda at the Nixon Library. It’s always a great show with lots of roses in a beautiful venue. I hope to participate. If you love roses, you should visit a show, even if you don’t enter any roses, especially one like this that is so close. It’s a great opportunity to learn which varieties do well in local areas, identify some for your garden and get acquainted with other rose enthusiasts. Also, you can stroll around the facility for free.

If you didn’t restart your fertilizer program last month, do it now. Make sure plants are thoroughly watered the day before you fertilize. I recommend organic types and alternating with one that includes fish emulsion. This time of year I suggest using a fertilizer that contains a greater percentage of (P) phosphate in relation to (N) nitrogen and (K) potassium to encourage stronger root systems and resistance to stress.

A soil test may indicate that you may need some other mineral to make the added phosphate available or if needed. Apply at two week intervals until mid-November.

If you apply a fertilizer dissolved in water early in the day, you can apply it right over the bush from top instead of at the base in a well. This application is in part a “foliar feed.” Good-sized hybrid tea roses generally need about two gallons of solution; a couple of days after application, give them a good hose watering to make sure the fertilizer has migrated down into the soil.

Dry granular products should be scratched into the soil surface around the base of the plant to drip line and watered in gently so as to not slop them into piles and pockets. Apply at the recommended concentration on the label.

If growing in pots, use half the recommended concentration but apply more frequently. Alternating with liquid and dry is most beneficial. The last day for fertilizing is 30 days before the “first frost date” which is around mid-November in the Temecula Valley.

A bi-monthly magazine which covers rose topics is the American Rose published by the American Rose Society. Visit http://www.rose.org for more information on obtaining it.

When you have a moment to spare, feel the need to get away or when the day cools down, take your favorite beverage and a picnic basket and visit the Rose Haven Heritage Garden, 30592 Jedediah Smith Road, in Temecula. The cross street is Cabrillo Avenue. Also, visit http://www.TemeculaValleyRoseSociety.org.