Weather prompts change in pruning plans

As I look back over my previous articles I noticed that since 2013 there is what I suggest is a new normal of high temperatures for August and September. The average day to night temperatures in the first 25 days of August were higher this year than nearly every day in August last year.

I checked the weather projections and learned that temperatures for the next seven to 10 days for Southern California are for mid-80s to low 90s, cooler than the 100-plus predicted one year ago for same period in September 2017. Add to that higher than normal humidity due to warmer ocean temperatures at local beaches.

For those who are participating in my prescribed practice of allowing a summer of rest for their roses, they still have several weeks to take it easy before completing a mid-season pruning. As a wise man once said, “Predicting things is difficult, especially in the future,” but I 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 will begin my mid-season pruning Sept. 1 in hopes of having blossoms for the American Rose Society National Convention, which will be hosted by the San Diego Rose Society, Oct. 25-29.

If there is a special event which requires fresh rose blooms, count back 6-8 weeks from that planned event to determine when to do that end-of-summer pruning. It’s possible to have two more bloom cycles this year. Remember, a mid-season 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 leaf with five leaflets.

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 succumb. Assess conditions every morning. Look for wilted or dry crisping foliage. Sometimes if discovered 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 a inspection isn’t done until the afternoon or evening it may be too late or the gardener 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 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.

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. This being said, 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 can be found in the Care for September 2013 newsletter at http://www.TemeculaValleyRoseSociety.org. If there are signs of yellowing foliage, there 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 the leaves have a fine webbing, a stronger method may be needed.

I’ve noticed another problem as result of the weather this year: high temps and humidity have increased instances of Black Spot as indicated by yellow leaves with usually round-shaped black spots. With the humidity comes dewy nights which tends to incubate powdery mildew.

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.

Now would be another good time to order composted mulch. Here is a formula use to determine the quantity needed. 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. Composted mulch is the best product to apply to protect rose 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 there is a moment to spare or the need to get away or when the day cools down, take a favorite beverage and a picnic basket and visit the local one-of-a-kind Rose Haven Heritage Garden, 30592 Jedediah Smith Road, in Temecula. Also, visit http://www.TemeculaValleyRoseSociety.org.