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By Frank Brines
ARS Master Consulting Rosarian 

Prepare rose bushes for warmer weather


Last updated 5/14/2019 at 9:31am

The Hoplia beetle is a native petal feeding insect that feeds on light-colored petals of many plants, including roses.

Residents may have noticed the effect of climate change again this year. As I speak with other rose gardeners, I learn that all are finding it more difficult to predict what to do and when as they have in past years. The timing and development of growth is dependent on weather, especially a more constant predictable rhythm of temperatures. This year temperatures and rain fluctuated more than I remember it in recent years. Flower production is affected greatly by inconsistent temperatures, sun and water as well. I've noticed unusual looking vegetation in form, color and distorted blooms. I have experienced more fungi in my garden. The increased rain stymied growth and allowed rust, mildew and Botritis fungus to flourish. When temperatures level out, then roses burst into growth.

I think that the hot temperatures will come as summer arrives. As such, I will share some tips for gardeners to do to get their next cycle of good blooms before it gets too hot. A minor pruning to remove old blooms will reset the cycle of blooming. For quicker re-bloom, prune back to the first outward facing five leaflet leaf. Most likely not all are at the same stage of development, so just prune back as blooms fade – don't leave them in the garden or put them in the compost pile – make sure to put them into the green waste barrel. Continue shaping the bush for best production by pruning the cane to an outward facing bud. Each leaf axis has a bud. Knowing this fact makes it easy to discern an outward facing bud. Attempt to keep canes that are larger than the diameter of a wooden pencil. Rebloom normally takes about six weeks with normal temperatures. That would make the next blooms appear around mid-June just before the summer heat. Knowing this information can help gardeners plan the preparation for hot summer in Temecula Valley.

Roses do like to eat and drink, so a constant supply of nutrients, including micro nutrients such as copper, iron, manganese, magnesium, etc. is mandatory. The soil microbiology is multi-tiered, abundant in beneficial microbes which create a sustainable soil diversity acting like an "immune system." Phosphate (N) and Potassium (K) help develop a strong root system and better blooms assisting in preventing 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 one lots of money, energy and guesswork for a fulfilling garden.

Organic amendments such as manure, compost or mulch stay where they are put, break down slowly and don't contribute to groundwater pollution, as long as it doesn't run off into drains. In addition, they improve the soil food web, so in the long run it uses less product while providing "food" for all the small creatures like earthworms who act like rototillers mixing them into the soil to lower depths. The best thing to do for a garden is to add a generous layer of mulch that doesn't have wood chips.

Gardeners may have experienced more fungi, mildew or rust, so far this year. Keep an eye for worsening conditions. Treating is dependent on how heavy the disease is, as well as the 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. There are some organic formulas using neem oil, insecticidal soaps, baking soda, etc. Do not use a formula that treats everything. Use a product specifically for a certain problem. Read entire labels and use accordingly and use safety equipment to avoid exposure to contaminants. Cover up any bare body parts when applying chemical treatments for disease or pests. Use approved goggles for eye protection, respirator mask, long sleeve shirt, water and 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 black spot and a new pest called chilli thrip which is much smaller than the western thrip that residents are accustomed to in their gardens and more devastating as they eat all varieties of vegetation. Control is quite difficult, and treatments are being studied. There are a few products being used which are still in research. Any product containing "Spinosad" seems to help.

I have a repeat invasion of the Hoplia beetle this year. It is a native petal feeding insect that feeds on light-colored petals of many plants, including roses. It is in the family Scarabaeidae with famous cousins like the green fig beetles which is among the worst pests on the East Coast. This pest is hard to control as today's pesticides are short-lived especially the less toxic insecticides. Even if those are used, collateral damage to other beneficial insect species will occur as with regular insecticides. Spray all light-colored roses as recommended on the label. To avoid collateral damage to bees and other beneficial insects and birds, I just choose to physically remove the beetles from affected blooms and drop them into a container of soapy water. Each one that is captured can possibly prevent tens of offspring next year as it is also mating season and they are laying eggs. The insect winter over in the ground as a grub.

It is never too late to apply a thick layer of mulch. I prefer composted mulch, not coarse wood forest products, applied to a depth of 4 inches. Pine needles are also good for mulch. The best way to keep an entire bed uniformly supplied with water is to apply a generous layer of mulch. It's the single most beneficial thing gardeners can provide for their plants. I recommend against using mulch containing wood chips of any sort. There are several reasons not to: Additional nitrogen must be supplied to replace the nitrogen needed to break down the wood fibers; also, a mold can result which can prevent fertilizers, water and oxygen from entering the root zone. Instead, I recommend composted mulch as it is well broken down and filled with nutrients ready to be integrated into the soil by worms.

I have grown many varieties of roses in my gardens. Most will grow well in the Temecula Valley. Heads up for something to prepare for in the coming months. Don't expect to have great roses during July through September when temperatures are in the high 90s. Just keep the plants as well hydrated as possible, and let them enter a short period of dormancy or slowed growth not to produce blooms which will likely be of poor quality and stress the plant as well. To do it, just remove petals from the bloom and discard into green waste bin. Leave the "hip" on the cane.

Some varieties I recommend are 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 and Violet's Pride.

I am an American Rose Society certified master rose consultant. For answers to questions, visit the TVRS website or email [email protected]

Visit Rose Haven Heritage Garden, 30592 Jedediah Smith Road, the cross street is Cabrillo Avenue in Temecula. Also, visit

Now, let's get out there and spread the word and the joy of roses.


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