Rose bushes need hydration and pruning

I checked the weather projections and learned that temperatures for the next 7-10 days in Southern California are for mid-90s to 115. Add to that higher than normal humidity due to warmer ocean water temperatures. All in all, temperatures are trending higher in the last five years. I advise you to thoroughly hydrate your roses over the next few days to prepare them for the high temps coming and continue to do so until cooler weather.

If you are using drip irrigation, run your system in the early evening to give your roses the opportunity to thoroughly hydrate. If you’re using a hose or other non-surface method, do it in the early morning – it’s best to avoid getting water on vegetation during these high temp days.

If you are following my prescribed practice of allowing your roses to rest during the summer, you still have several weeks to take it easy before a midseason pruning.

As a wise man once said, “Predicting things is difficult, especially in the future,” but one can only assume it will look a little like the past, especially with the weather.

So, I'll give it a try: This year I had planned to do my midseason pruning first week of September. Since there will be no fall rose shows and I have had an infestation of chilli thrips and due to projected high temps, I will remove all infected growths and then prune as I have time. Be careful of removing too much vegetation that would expose canes to the hot sun and sunburn which could kill the cane.

If you have a special event for which you would like to have fresh rose blooms, count back 6-8 weeks from that planned event to determine when you should do your end-of-summer pruning. You can possibly have two more bloom cycles this calendar year. Remember, a midseason pruning is light, removing any point along a cane where many stems of blooms came out. For quicker repeat blooming, prune each cane back to just above the outward facing bud at the base of the first five leaflets leaf.

During periods of sustained high temperatures, 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 be severely damaged or killed. Assess conditions every morning. Look for wilted or dry crisping foliage. Sometimes if you discover it soon enough, dousing the stems and leaves with plenty of water in addition to applying plenty of water to the ground, may save the plant.

If you wait to inspect until the afternoon or evening it may be too late or you might not get a good assessment of the plant’s condition: After a hot day, most plants can appear wilted while still receiving sufficient hydration. Also inspect your 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: Replace it.

Plants in pots require more frequent watering than those in the ground. As the soil dries it pulls away from the sides of the pots allowing water to run through the soil without penetrating the soil. Sun shining on the pot (whether black plastic or clay) can steam the roots of the plant which also requires more water to maintain a cooler temperature of the soil. Plastic is still preferred over clay as clay loses moisture through its many pores.

Double potting can moderate drying. This practice would at least have a curtain of cooling air between the pots, an insulation of some type would be more efficient. One more thing: The longer the soil is in a pot, the less porous space is available in the root zone – so repot every two years or so.

This time of year, with hot temps also attracts spider mites. This topic was covered in a previous care column which you can find on http://TemeculaValleyRoseSociety.org newsletter; look for “Care for September 2013.”

If you see signs of yellowing foliage you may have an infestation. Check the underside of the lower leaves for grainy feeling substance or tap onto a paper to see these very small critters. The easiest way to treat is to use strong spray of water from below to give the plant a shower and rinse the mites to the ground. If you see fine webbing you may need a stronger method.

I’ve noticed another problem as result of the weather this year: High temps and humidity have increased instances of black spot, which is indicated by yellow leaves with usually round shaped black spots. I have not seen any sign of black spot in my garden yet. With the humidity comes dewy nights which then tends to incubate powdery mildew. I have been troubled by this mildew throughout this year in my garden. I have discovered damage from chili thrips, however that is difficult to recognize until it becomes obvious. At the first signs of any of these it is best to start treating with fungicide or a pesticide, preferably one containing Spinosad. See my article for August.

After the pruning has been accomplished and at least one thorough application of water, apply a good fertilizer. Read the directions on the container to discern type of application and what to do. I use granules, powder or liquid and water it in for the quickest effect. My colleagues are recommending the use of fish emulsion and seaweed fertilizers at the rate of 1 tablespoon each per gallon of water applied now. Remember: Never fertilize a dry or stressed plant – always water the day before.

Now would be good time to order composted mulch. Here is a formula you can use to determine the quantity you will need. An area 10 feet by 50 feet needs 4-5 cubic yards to cover the garden 3-4 inches which is the depth I recommend. This is the best product you can apply to protect your roses roots from heat and cold.

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

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