Prune and mulch to keep roses healthy
Last updated 5/14/2020 at 2:39pm
There were signs of climate change again this year. The area had above average rainfall and fluctuations in temps, which was good and bad. It is more difficult to predict what to do and when as I have in past years. The timing and development of growth is dependent on weather, especially a more consistent predictable weather pattern.
This year, temperatures and rain fluctuated more than I remember it doing in the past decade. Flower production is impacted greatly by inconsistent temperatures, sun and water. The increased rain stymied growth and caused some rust, mildew and Botritis fungi to appear quickly. I was able to get several applications of chemicals for fungi before the weeks of rain. Still some rose leaves were affected with rust and lots of Botritis.
Abundant sunshine and water produce larger blooms. In my garden, applying fertilizer every two weeks before all the rain resulted in more growth and buds. If you didn't apply fertilizer during all that rain, be sure to do so soon, along with plenty of water to maintain this production curve. Be vigilant for changes, diseases and pests in the garden now. Be prepared to act on these immediately.
Blooms mature quickly in warm weather, so as blossoms fade, lightly prune back to the first outward facing five-leaflet leaf. Don't shorten the cane too much. If you remove just blossom and peduncle, you may get two weaker shoots with less bloom quality. This light pruning sets the stage for the next bloom cycle in about seven weeks.
For best production, try to shape the bush to outward facing buds. If you can, keep canes that are larger than the diameter of a wooden pencil. Doing all this pruning now, the next blooms will appear around mid-June before the summer heat. Knowing it can help you prepare for the hot summer in Temecula Valley. Make sure to put all vegetation into your green waste barrel.
Roses want a constant supply of nutrients, including micro nutrients, such as copper, iron, manganese, magnesium, etc. Remember that you are also feeding the soil microbiology which is complex and multi tiered, abundant in beneficial microbes which create a sustainable soil diversity acting like an "immune system."
Phosphate (N) and potassium (K) help develop strong root systems, better blooms and help prevent stress during adverse conditions. In fact, plants grown with organic fertilizers are themselves more resistant to pests and diseases. A soil test kit for analyzing the soil needs could save you lots of money, energy and guesswork for a fulfilling garden.
Organic amendments such as manure, compost or mulch stay where you put them, break down slowly, don't contribute to groundwater pollution by preventing runoff into drains, improve the soil food web, so that in the long run you end up using less product while providing "food" for all the creatures like earthworms who act like rototillers mixing them into the soil to lower depths. The best thing you can do for your garden is to add a generous layer of mulch that doesn't have wood chips.
Keep an eye for worsening conditions such as water stress, insect pests and fungal diseases. Do not use a formula that treats everything. Use only a product especially for the specific problem and treat in proportion to severity, as well as your level of acceptance. If control is lost, it may be necessary to strip off all of the diseased leaves and prune back and basically start over.
Some organic formulas use neem oil, insecticidal soaps, baking soda, etc. Read entire labels and use according to directions, including safety equipment to avoid exposure to contaminants. Keep your skin covered when applying chemical treatments. Use approved goggles for eye protection, respirator mask, long sleeve shirt, water/chemical resistant boots and gloves. When the treatment is completed, immediately remove clothing and wash. Take a good shower to remove any possible contamination.
Gardens are showing increased prevalence of the fungal disease "black spot." It appears as dark green to black spots on leaves, which often turn yellow and fall off. The infected leaves, even those that fall, produce spores that can infect other leaves. There are many fungicides available, but control can be difficult. Sometimes you just have to remove and dispose of any affected leaves.
Another new pest is the chilli thrip. It's much smaller than the Western thrip we're accustomed to and more devastating as it eats all varieties of vegetation. Control is quite difficult and new treatments are being studied. Products containing Spinosad bacteria seem to help control soft-bodied larvae, but be aware that even such "natural" products can kill other beneficial insect species.
It is never too late to apply a thick layer of mulch. Use composted mulch, not wood products. Pine needles are good too. Apply to a depth of 3-4 inches. Mulch keeps the entire bed uniformly supplied with water. Avoid mulch containing wood chips of any sort: Their breakdown robs the soil of nitrogen, and a mold can grow that is impenetrable to water, fertilizers and oxygen.
I've grown many varieties of roses in my gardens. Most will grow well in the Temecula Valley. Some varieties I recommend: Mr Lincoln. Outta the Blue, Easy Does It, Touch of Class, Double Delight, Joey, Gold Medal, Graham Thomas and Fragrant Cloud.
Heads up for a high heat summer. Don't expect great roses during July to September when temperatures are high. Just keep plants well hydrated and remove spent petals, leaving the "hips." Don't prune. The plants will enter a short dormancy and build strength for fall.
I am an ARS certified master rose consultant. If you would like personal answers to questions, you can leave questions on the TVRS website or write me at [email protected]
And when you've got a moment to spare, visit Rose Haven, 30592 Jedediah Smith Road, in Temecula. The cross street is Cabrillo Avenue. Also, visit https://www.TemeculaValleyRoseSociety.org.