by Frank Brines, ARS Master Rosarian
I always enjoy looking back to last year’s care column for the month. According to weathercurrents.com, the “normal” (30-year average) for October in Temecula is 83o/54o, but we’ve all seen some real scorchers every now and then, even this late in the year. 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 o to 100 o range (and with a potentially extreme UV Index) don’t remove so much foliage that the canes are overexposed to fierce direct sunlight, because sunburn can damage or kill even healthy canes or entire plants. The risk is even greater 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 90o temperature for a rosebush 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, this is even more critical.
Morning is the best time to assess your garden’s condition. Look for wilted or dry, crispy foliage. If discovered soon enough, dousing severely stressed plants with plenty of water may save them. If you wait until the afternoon or evening to inspect, it may be too late. After a hot day, even plants receiving sufficient hydration may appear a little wilted, so checking in the afternoon can 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 unglazed clay pots require more water because the surface of the pot evaporates moisture, which has the benefit of cooling the roots (which tend to colonize the space between the soil and the pot), but that also promotes drying. Plants in plastic pots evaporate water at a lower rate, but if the pots are in direct sun that inner pot surface can become very hot. 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, but only if the water is not allowed to remain in the saucer for longer than a day—if it is chronically wet, it can deprive the lower regions of the pot of the oxygen that the roots need for good health. (So, it’s all kind of a balancing act!)
Spider mites and Chilli Thrips are common problems in hot, dry, dusty conditions. This topic was covered in the September care column. The treatment with the lowest environmental impact is a good, strong spray of water applied maybe every three days or so to the top and bottom leaf surfaces. Do this before the sun is at full intensity because water droplets on the surfaces may act like magnifying glasses. If the pests are still a problem, prune away the thrips-deformed stems and leaves (into the green waste bin) and make a couple of applications, 5 to 7 days apart, of any product containing Spinosad. My garden was attacked by Chilli Thrips in mid-September, which I then had to cut away the worst and try saving others by spraying. I hesitate to recommend spraying more than a couple of times in any month because, like any chemical control method—even an organic one—too frequent application can “select for” those few individuals that have mutations making them able to survive treatment. When those critters get established, you’re faced with a more challenging situation.
Other pests which can result from the hot weather are rose slugs, the small green “worm” which is the larval stage of rose sawflies/cane borer. Also common are spider mites, soft-bodied scale, caterpillars, and inchworms. Lacewings (a beneficial insect) may have visited your garden this year. If so, they may have laid eggs on the underside of leaves hanging by thin thread-like string. Gardeners often overlook these and then prune off and throw away the stem. Examine the bush from below to find them.
If you didn’t restart your fertilizer program last month, do it now. Watch the forecast for a day that will be below 90o, and water the plants thoroughly the day before. I recommend organic types and alternating with one that includes fish emulsion. This time of year, I suggest using a fertilizer with a higher percentage of (P) phosphate relative to (N) nitrogen and (K) potassium to encourage stronger root systems and stress resistance. A soil test may indicate that you may need some other mineral to make added phosphate available or if needed. Apply at two-week intervals until the end of October.
If you apply 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 then watered gently to promote penetration and avoid slopping the fertilizer into piles and pockets. Apply at the recommended concentration per the label. If growing in pots, use half the recommended concentration but apply more frequently. Alternating with liquid and dry is most beneficial.
Plenty to do, but all of this will help promote abundant Fall blooms. 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, Temecula (cross street is Cabrillo Avenue). Also, visit our website, www.TemeculaValleyRoseSociety.org. Spread the joy of roses!
Membership in the American Rose Society (ARS) will grant you access to the American Rose, a valuable digital (online) magazine which covers a wide range of rose topics. Go to www.rose.org for more information on joining.
