The next two weeks’ weather forecast looks like southwest Riverside County is back to a period of more normal temperatures for this time of year, but Santa Ana winds could show up anytime now. Gardeners should make sure to check their irrigation system if they haven’t after the heat of summer. Roses should be actively recovering from the light fall pruning they received in September.
I gave instructions for midseason pruning with a suggested timeline for pruning and restarting a feeding program. What may not have been clear is that it is meant to be a light pruning and must be carefully calibrated with the weather conditions. Specifically, when temperatures remain in the 90-plus range, gardeners must take care to not remove too much foliage because it can overexpose canes to the fierce sun, resulting in sunburn, which can damage or kill otherwise healthy canes or the entire plant.
If a gardener is planning to have roses for a special occasion later this year, it will take hybrid teas six to eight weeks from this pruning and feeding; floribundas and miniatures will take a little less time. This cycle of bloom is the second best of the season and necessary to achieve maximum potential. Exhibitors are pruning and planning in time for the fall shows in the Pacific Southwest District. Two shows of interest are in Palm Desert, Nov. 9, and in Mesa, Arizona, Nov. 16.
After pruning, restart a feeding program. Make sure the plants are thoroughly watered the day before feeding. I recommend organic types and alternating with fish emulsions. Use a fertilizer that contains greater percentage of (P) phosphate in relation to (N) nitrogen and (K) potassium. It will encourage stronger root systems and thus boost resistance to stress. If temperatures are in 90s or above and a gardener does not choose to use organics, they should hold off fertilizing until weather cools down. If they use a fertilizer that is first dissolved in water, apply it right over the bush from top to bottom. A hybrid tea needs about 2 gallons of solution and should be watered in after a couple of days. If they use a dry granular product, scratch it into the soil surface around the base of the plant to drip line, and water it in. Apply at the concentration recommended on label. If growing roses in pots, use half the recommended concentration but apply it more frequently. Repeat these applications every two weeks. The last date for fertilizing is 30 days before the frost date, which is around mid-November in the Temecula Valley.
When temperatures continue to be in the 90s, it is necessary to ensure plants receive adequate water to stay hydrated. It takes only a few days in these temperatures without sufficient water for a bush to become seriously stressed and damaged. I suggest that hybrid tea rose bushes can survive with 3 gallons of water twice a week, so make that the absolute minimum. A layer of 4 inches of mulch will greatly reduce evaporation of soil moisture. The composition of soil effects the time for soil to dry out. Recent rain though hardly enough to change much does help in bathing the leaves with moisture. Soil dries out more quickly due to less water being applied, in general. With potted roses, it is even more critical. Assess conditions every morning. Look for wilted or dry, crispy foliage. If it is discovered soon enough, dousing with plenty of water may save the plant. If the inspection isn’t done until the afternoon or evening, it may be too late or it might not be a good assessment of the plant’s condition: After a hot day, most plants can appear a little wilted while still receiving sufficient hydration.
Also inspect the irrigation system to make sure it is delivering enough water, isn’t clogged and isn’t over watering – all problems that come with age in drip irrigation systems. If an emitter is delivering much more or much less water than others on the line, it can change the system pressure and affect the other emitters. The simple solution is to replace it. If a clay pot is used, more water is needed as the clay will absorb moisture from the potting soil and evaporate through the porous clay material. Plastic pots are better as they will not absorb moisture from the soil. Another possible problem with potted plants is the soil 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. Most people use black plastic pots as containers, these tend to heat the soil in them from the sunshine, which is an added reason to check these plants frequently for soil pulled away from the sides and damaged roots from the heat. Ideally these pots should be placed in another larger one for some insulation.
It’s not too early to start thinking about which roses to remove and what to replace them with. Very few suppliers have catalogs any longer but most have online catalogs. If the roses have not been mulched recently, estimate the amount of composted mulch needed to cover the garden beds 4 inches deep and plan to buy it for this coming winter or spring. An area 10 feet by 5 feet will require 4-5 cubic yards of mulch.
Spider mites are a common problem when hot, dry, dusty conditions prevail. This topic was covered in a previous care column which can be found on www.TemeculaValleyRoseSociety.org in the newsletter; look for Care for September 2013. There has been a more recent invasion by chili thrips, which are even smaller than the thrips encountered in the past. They can do more damage and quicker. Control requires constant vigilance and spraying sadly. Some control has been achieved with use of a Spinosad bacterial spray, which I have used with some success on early detection of the symptoms. For more serious symptoms or delay in treatment, consult the local horticulturist or county extension for chili thrip pest management to identify more effective pest management alternatives. In all cases, read the label carefully for what it treats and apply it by carefully following all directions.
A valuable bimonthly magazine which covers rose topics is the American Rose published by the American Rose Society. Visit www.ARS.org for more information on obtaining it.
If someone has a moment to spare or feels the need to get away, or when the day cools down, take a favorite beverage and a picnic basket and visit Rose Haven Heritage Garden, 30592 Jedediah Smith Road, in Temecula. The cross street is Cabrillo Avenue. Also, visit www.TemeculaValleyRoseSociety.org. Spread the joy of roses.