By Frank Brines
ARS Master Consulting Rosarian 

Climate change challenges rose gardeners

 

Last updated 5/12/2018 at 8:25am

The hoplia beetle eats light-colored flower petals.

If you feel like your garden just doesn't seem to be responding as it has in years past, you just may have noticed the effect of climate change. 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. It makes planning rose shows a year in advance most vexing.

The timing and development of growth is dependent on weather, especially a more consistent and predictable rhythm of temperatures. Flower production is affected greatly by inconsistent temperatures, sun and water as well. I've noticed shorter canes, unusual looking vegetation in form and in color and distorted blooms. In my garden, there are not as many blooms per bush, more fungi than in past and bloom disease.

I think that the hot temperatures will come as summer arrives, so here are some things that you can do to get your 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 second bloom, prune back to the first outward-facing, five-leaflet leaf. Most, likely not all, are at the same development, so just prune back as blooms fade – don't leave them in your garden or put them in your compost pile – make sure to put them into your 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 makes it easy to discern an outward-facing bud. Attempt to keep canes that are larger than the diameter of a wooden pencil.


Roses do like to eat and drink, so a constant supply of nutrients is mandatory. The soil microbiology is multi-tiered, abundant in beneficial microbes which create a sustainable soil diversity acting like an "immune system."

Potassium helps 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 you put them, break down slowly and don't contribute to groundwater pollution as long as you prevent run off into drains. In addition, they improve the soil food web, so in the long run you end up using less product while providing "food" for all the small creatures like earthworms who act like rototillers mixing them into the soil to lower depths.

You may have experienced more fungi – mildew or rust – this year. Keep an eye for worsening conditions. Treating is dependent on how heavy the disease is, 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.

There are some organic formulas using neem oil, insecticidal soaps, baking soda, etc. Do not use a formula that treats everything. Use only a product especially for the specific problem. Read entire labels and use accordingly and use safety equipment to avoid exposure to contaminants.

Gardeners must cover up bare body parts when applying chemical treatments for disease or pests. Use approved goggles for eye protection, respirator mask, long-sleeved 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 currently in our gardens and more devastating as they eat all vegetation. Control is quite difficult, and treatments are being studied. There are a few products being used which are still in research.

This year I discovered a bug that I'd never encountered before in my garden. My entomologist friend identified it as the hoplia beetle. It is a native petal feeding insect that feeds on light-colored petals of many plants, including roses unfortunately. It is in the family Scarabaeidae with famous cousins like the Japanese beetles which is among the worst pests in the East Coast.

This pest is very hard to control as today's pesticides are short-lived, especially the less toxic insecticides. Even if you use those, collateral damage is just like those of regular insecticides, and you would have to spray your 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 them from affected blooms and either squish them or drop them into buckets of soapy water.

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 act you can provide for your plants.

I recommend against using mulch containing wood chips of any sort. There are several reason 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, but heads up for something to prepare for in coming months. Don't expect to have great roses during July through September when temperatures are in the high 90s. Just keep the plants well hydrated as possible, 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.

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.

Frank Brines is a American Rose Society certified rose consultant. For personal answers to questions, comment on the Temecula Valley Rose Society website or email roseguy2000@aol.com.

Also, visit the Rose Haven Garden, 30592 Jedediah Smith Road; the cross street is Cabrillo Avenue in Temecula. For more information, visit http://www.TemeculaValleyRoseSociety.org.

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

 

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