Roses should recover from fall pruning

Looks like the valley is back to a period of more normal temperatures for this time of year, but the Santa Ana winds could show up anytime now. Gardeners should make sure to check the irrigation system if they haven't after the heat of summer. Roses should be actively recovering from the recent light fall pruning.

Last month I gave illustrations and descriptions for mid-season pruning with a suggested timeline for pruning and restarting a feeding program. What may not have been clear is that it is a light pruning, and it must be carefully calibrated with the weather conditions. Specifically, when temps 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 even 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 is necessary to achieve maximum potential. Exhibitors are pruning and planning to time for the fall shows in the area and Arizona.

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 phosphate in relation to nitrogen and 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 use organics, they should hold off fertilizing until weather cools down. When using 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 it should be watered in after a couple of days.

When using a dry granular product, scratch it into the soil surface around the base of the plant to drip line, and be watered it in. Apply at the concentration recommended on label. If growing in pots, use half the recommended concentration but apply it more frequently. Repeat 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 even damaged. I suggest that rose bush 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.

This year the soil dries out more quickly than in previous years due to less water being applied as in previous years and, in general, the dryer soil environment. With potted roses it is even more critical. Assess conditions every morning. Look for wilted or dry, crispy foliage. If discovered soon enough, a dousing with plenty of water may save the plant. If a gardener waits to inspect until the afternoon or evening it may be too late, or they might not get 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 with what to replace them. Few suppliers have catalogs any longer, but most have online catalogs. If the garden hasn't been mulched recently, estimate the amount of composted mulch needed in order 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.

A common problem when hot, dry, dusty conditions prevail is spider mites. This topic was covered in a previous care column which can be found on the http://www.TemeculaValleyRoseSociety.org newsletter; look for Care for September 2013.

There has been a more recent invasion by chili thrips, which are even smaller than the thrips gardeners have 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 local rose show that gardeners may want to put on their calendar is coming up in San Diego, Oct. 27. Information on the National Rose Show Convention can be found at http://fiestaofroses.org.

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

When the day cools down, take a favorite beverage and a picnic basket, and visit the local Rose Haven Heritage Garden, 30592 Jedediah Smith Road, in Temecula. Also, visit http://www.TemeculaValleyRoseSociety.org and spread the joy of roses.