What is your tolerance for insect damage and fungal disease on roses?
It is a personal question and the answer can change depending on the uncontrollable factor of weather or the amount of time you have to devote to roses or your personal philosophy of what is the right way for you to garden.
I prefer to not use insecticides in my garden because I have fruit trees and mason bees that I nurture for pollination of my fruit. When aphids come to visit my roses, I often see ladybugs working on them, but I often get my hose with a medium spray nozzle and blast aphids with water for a few days in a row. The aphids fall to the ground and since they cannot fly, most do not return. If they are not removed, aphids continue to reproduce and damage roses.
If we have a hot dry June and July and I suspect spider mites will be active. Again, get the hose out with a spray nozzle. Spraying water and a slight rubbing of the leaves, especially on the undersides will deter the spider mites. So the word “spray” is not a bad word in my garden. I spray water, I spray liquid seaweed, I have been known to spray chelated iron and products approved for organic gardening.
Fungal diseases can do a lot of damage is a relatively short period of time. Once you see the damage, you cannot return the foliage to perfect again. As soon as a fungal disease shows, it is best to trim off (not tear off) the disease and do what you can to stop it from spreading. Some roses are resistant to fungal disease by hybridization. That is why you may see one or two roses badly defoliated (in a public garden for example) while others in the area stay clean.
The photos are examples of the continuum of possibilities for your rose garden. The amount of time you have to spend in the garden may change from year to year. Do not get discouraged if pests and disease appear. Contact a local Consulting Rosarian for help.
This is the first of four posts to supplement the information that will be presented on February 25th at 2:15- 3:45 in the Rainier Room.
Roses will uptake maximum nutrients when the soil pH is between 6.0 and 6.5. This reading changes in different locations of the garden. Other factors that change pH include use of chemical fertilizer and when the pH is tested, before, during or after the rainy season. West of the Cascades, the native soil tends to be acidic. (East of the Cascades the soil is alkaline) My Kitsap garden beds have had readings on October 2, 2016 between ph 4.5, pH 5.0 and pH 6.2. I applied granulated lime according to directions on the bag after these readings. You may have heard that lime is a slow acting soil amendment. I waited three months, until late December, to find pH in all rose beds to be pH 6.3 and pH 6.6.
I did not think this chart would project very well in the Rainier Room and even if it were projected, it seems to me to be something to study to fully understand.
I was moved to action this summer after reading a blog entry by my Minnesota friend Jack Falker pH of your garden soil is not uniform. pH is the amount of acid (H+) or base (OH-) in the material. Numbers 0 to 6.9 are acidic, with 0 being extremely acidic. 7 is neutral (deionized water). Numbers 7.1 to 14 are basic, with 14 being extremely basic (caustic and alkaline are also commonly used terms for basic). Although most references differ, roses generally enjoy a pH of 6.0 through 6.9, with about 6.5 being ideal. In other words, the soil should be just slightly acidic. For pH outside this range, the availability of nutrients to the plant is greatly affected. For example, at a pH of 5.0 or less, phosphorous is ‘trapped’ by aluminum ions and rendered insoluble which cannot be absorbed by the plant. In the 6.0 to 6.9 range, all nutrients are in a form that is available to the plant. The more basic the soil, the less nutrients, such as iron, nitrogen, and manganese, can be absorbed.
pH of the Native soil in my rose garden is within recpmmended range.