Too much mulch could be choking those prized roses
Roots need healthy drainage and a good flow of air or they can suffocate
Q: I purchased a dozen winter hardy rose shrubs a number of years ago for my retaining wall in the centre of a circular driveway. We filled the structure with topsoil, used black cloth for weed control, and covered the soil surface with rock.
The roses winter well, flower heavily and I cut them back above ground level in the fall. Two or three years ago I noticed the rose branches drooping on the stones. The base of the branches is yellowish brown and it looks like they have withered or decayed. The branches are literally choked off and are easily pulled off.
I tried an organic pest spray that didn’t work and then sprayed a Malathion treatment, but the problem persists. There is a separately located Hansa rose that is similarly affected. What do you think is causing this problem and is there a fix?
A: When I wrote back to this reader asking for more information, she revealed that she had previously planted Amur cherries that did not survive, in the same spot.
This makes me think the problem isn’t with the roses, but may be with the soil in the retaining wall planter or with the rock mulch. If the rock layer is deeper than two or three inches, the plant roots may not be getting air and moisture or the moisture that does get through is stagnating at the root level and causing rot. Removing some of the mulch could solve the problem.
Amur cherries are notorious for being very fussy about where their roots are. If the soil does not drain properly or if there is a lot of clay in the soil, they will suffer.
The other possibility is a problem with the soil itself or something in the soil. I recall a problem with a series of birch-tree plantings that kept dying in the same location. It turns out the homeowner regularly used Drano to clear out slow running drains and eventually it was found that the Drano was seeping from a tiny hole in the sewer line and killing every birch that was planted in the area. If the mulch is the right depth, I would check the soil. You can send it to a soil lab for analysis to help determine the problem.
If neither the mulch nor the soil is the issue, let me give you a list of things to check on the roses: ❚ Watering: Both too much or too little water can cause a rose to wilt or droop. ❚ Insects: Check the leaves and the flowers closely for aphids and thrips. Aphids are small, green insects, and thrips are extremely small, yellowishbrown insects. If you find evidence of these invaders, treat the plant with a permethrin-based insecticide such as Doktor Doom House and Garden or Ambush. ❚ Powdery mildew: Check the leaves for this powdery, whitish, chalky substance. The mildew itself will not cause drooping but can cause leaf curl that mimics dropping. If you find powdery mildew, treat it with Serenade. Q: Can you tell me why my peas are dying from the bottom up? Last year we had a great crop, but this year we have had no maturing peas and all the plants are dying. A: The problem might be fusarium wilt. This is a fungal disease. The only way to control it is to use peas that are resistant to the wilt and to plant as early as possible. The early planting allows the plants to develop before the soil temperatures reach the optimum level for the development of the fungus.
Rotating the crops every five years is also a good idea.