How to keep rose bushes healthy
Last updated 5/13/2021 at 8:33pm
There were signs of climate change again this year. Temperatures and rainfall patterns differed greatly from last year, with temps lower for longer, and much less rain and spread out over a longer period. Rose growth and development are dependent on weather, and flower production is particularly impacted by inconsistent temperatures, sun and water. All of this has made it more difficult for me to predict what to do and when to do it!
The longer time frame for rain and more misty cool nights caused some rust, mildew and Botritis fungus to appear quickly. Blooms were affected by botrytis which "rots" the petals preventing them from opening successfully. A few warmer days would encourage growth and produce buds, then a few days of 70–80-degree temperatures caused a burst of growth toward blooming. At least one application of fungicide and pesticide spray helped to reduce the outbreak.
Personal commitments caused me to delay my pruning this year by three weeks. Even so, the first roses bloomed about eight weeks after pruning. Typically, the first flush of blooms is expected after eight to 10 weeks, usually on the longer side. Those roses are now in need of pruning again. In this area, the first annual rose shows would usually be about now, and I know that local exhibitors' roses are in all different stages of bloom, many past exhibit stage.
Abundant sunshine and water produce larger blooms, so your roses are probably really ready to take off. If you didn't apply fertilizer earlier, be sure to do so soon (more about this a little later), along with plenty of water to maintain this production curve. Know the soil composition in your garden so you know how much water to apply to maintain good soil moisture without drowning the roots.
Be vigilant for changes, diseases and pests in your garden now, and be prepared to act on these immediately. The Hoplia Beetle appeared in April with the few hot days. I usually see it in May so it was a few weeks early. It can do serious damage in a short time to the rose blooms. It can first be seen on light colored blooms. Drag it out from between the petals with a screwdriver or Q-tip and plop it into a cup of sudsy water.
(Note: To learn to identify Hoplia Beetles, just do a search on the Internet. Bottom line however: If you find little holes in light colored petals, and you find beetles nestled between the petals, you've probably got Hoplia – dig 'em out!)
Blooms mature quickly in warm weather, so as they fade, lightly prune back to
the first outward facing five-leaflet leaf. Don't shorten the cane too much. If you
remove just the blossom and peduncle (this little length of stem that ends at the
blossom), 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 now, your next blooms will appear mid-June before the summer heat. Knowing this, 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 (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 creates a sustainable soil diversity acting like an "immune system."
Phosphate (N) and potassium (K) help develop strong root systems, better blooms, and helps 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.
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 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 to 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,
Fragrant Cloud, Fragrant Plum, Sunsprite, Playboy, Sally Holmes, Ballerina,
Tropical Lightening,Hey Jack, Neptune, Violet's Pride.
Heads up for high summer: Don't expect great roses July through September
when temperatures are high! Just keep plants well hydrated, and remove just
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
And when you've got a moment to spare, go visit Rose Haven, located at 30592
Jedediah Smith Road (the cross street is Cabrillo Avenue) in Temecula. Also,