Rose Care FUNdamentals – December 2022

by Frank Brines, Master Rosarian (ARS)

Perhaps gardeners are among the first to experience the effects of climate change. Gardeners have increasingly been experiencing diseases and critters never before seen in our region. Many are results of the changing climate which brings new and unfamiliar environments from other regions. One recent example of this, in my opinion, is the cancellation of the Palm Desert rose Show on November 12, 2022. Reportedly major rose exhibitors informed the Show committee that their roses suffered severe damage from Chilli Thrips and the unusual high-temperature Fall weather. In my nearly 40 years of  growing roses in the Pacific Southwest District this is the first show cancellation to my knowledge. 

I mentioned last month that the Asian “chili thrip” is spreading rapidly in the Southwest and is becoming a global threat. This pest is extremely successful and particularly resistant to conventional control methods. The chili thrip is even smaller than the western thrips we’re familiar with. It works in similar ways, only more devastating and more difficult to control. It doesn’t seem to have any preferences except new growth of almost any plant and blossom. Its damage resembles the effects of Roundup over spray or rose virus: severely stunted and very narrow leaves, stems, and buds. Gardeners I’ve spoken with use several different products to gain some control, but a regular program is necessary with applications weekly at least. 

All of this should lessen your feelings of insecurity if your garden has not performed to your expectations this past season. I’ve heard many complain that pests and disease were out of control in August/September. (Personally my garden was unattended for weeks in August and fell into that category as well, but that’s on me!)

If you’re in this situation, the only practical road to control is to prune out the affected parts and consign them to the green waste bin. Then immediately apply a chemical insecticide spray and begin a spraying program as directions indicate or, every 7-10 days until control is reached, then at two weeks intervals.

Depending on which side of the valley you live, weather has been relatively good for our fall roses. Roses were still be seen actively growing and blooming in many Temecula Valley gardens during the Thanksgiving holiday, as most areas still haven’t had low temperatures anywhere near frost which, on average, occurs in mid-November.  Normally, lower nighttime temperatures cool the soil and reset the roses’ biological clock to slow down and go into a kind of dormancy. Roses need a four- to six-week dormant period during the winter months to allow them to undergo natural hormonal changes that prepare them for the next growing season, including forming buds at the base of the plant to produce new canes. At this point, aside from pruning away diseased branches (as described above), I encourage you to not deadhead or prune until late January to early February.

Be sure to monitor your plants when daytime temperatures are warm: They still need to be kept hydrated! Also, do NOT fertilize until after your major pruning in January or February—I’ll provide thorough information on all that early next year. Speaking of fertilizer, the San Diego Rose Society is currently taking annual fertilizer orders for January delivery to have on hand when new spring growth is 2”-3” long; go to their website for more information: https://www.sandiegorosesociety.com/fertilizer-sale.

There is still time to order that new rose you have been dreaming about. Garden stores may still be adding to their list of orders, or go to your favorite online nursery and make your order. There are many fine new roses that you simply must have. Many are more disease resistant than in the past. Most nurseries or wholesalers no longer print catalogs, so for a list of current roses available from each you will have to go online. Walter Andersen Nursery will soon have recently potted roses available. You can view the varieties that will be in stock by going to their website. I’m sure other nurseries will have similar information on their websites.

A few new varieties I find of interest are: At Last (floribunda, good apricot color, fragrance, disease-resistant); Bordeaux (floribunda/WineRed, large blooms, heat tolerant, disease resistant); Easy Spirit (floribunda/White, Hybrid T form, fragrance, hybridizer Tom Carruth, disease resistant, lasting form); Frida Kahlo (floribunda/Scarlet Redstriped gold, small clusters, mild fragrance, disease resistant, compact, hybridizers Christian Bedard & Tom Carruth); Gaye Hammond  S (Bright Yellow with touches of orange, slight fragrance, disease resistant, bloom making machine); Parade Day (Grandiflora/Fuchsia Pink Striped White, strong fragrance, hybridizer Christian Bedard, holds color); Flowerland (Shrubby, Pink, low (1.5′) growing habit, 60—65 petals, fragrant; it would be great for small spaces or en mass); Golden Iceberg (mild spicy fragrance).