Gardening expert explains how to avoid plant disease and other backyard challenges
Washington Post gardening columnist Adrian Higgins offered advice in a recent online chat.
Washington Post gardening columnist Adrian Higgins answered questions recently in an online chat. Here is an edited excerpt.
I’ve given up on my roses this year, but looking ahead to 2022, what is the best treatment to prevent black spot?
Roses need to be planted in an area where it is breezy, or at least not with stagnant air, as you might have where fences come together. You need good garden sanitation — remove all leaves as they yellow and pick up all the fallen ones, including the ones from last season. Correct pruning to open up the center of a bush is important, too, but the most effective way to counter black spot is to first buy varieties that have been specifically bred to be resistant.
I have a backyard with mature zoysia grass that I really like, but now have a problem with creeping Charlie, which is spreading in the summer heat. I do weed by hand, but often I find that I remove the leaf but not the runner. I am averse to using chemicals and wonder whether you have any suggestions for the removal of this pesky weed.
I have observed zoysia for a long time but haven’t grown it. But its weed resistance is based on the fact it knits together to prevent other plants from getting a purchase. So you’re creeping Charlie is probably just growing on the surface, and the runners should pull out quite easily. This weed also likes moisture, while zoysia will take dry conditions (within reason), so you want to pull back on the irrigation for that area and see if that stunts the weed.
I am contemplating seeding my backyard in “lo-mow” grasses, which are fine fescue. The website says that I live in a “transitional” area for this grass (Southeast Pennsylvania). I am growing older and need to mow less, but I don’t like the brown color of zoysia. Any thoughts on “lo-mow” grasses?
Fine fescue is used for more shady areas. It is not as robust as turf type tall fescues and won’t take a lot of foot traffic. I think tall fescues will do better for you, especially if the conditions are halfway decent, and you pick one of the new and improved varieties developed for the transition zone (actually a blend of two or three of them). If you don’t want to mow at all, you could put in some suitable ground covers or some lower growing ornamental grasses or sedges, but installing those will require initial work and cost.
What would be a good plant, maybe a ground cover, for alongside a house that is constantly in the shade? The area is damp and prone to puddles after heavy rains.
I would consider some robust ferns such as ostrich, royal or cinnamon fern, a lot of them, as well as hardy and swamp hibiscus.
I recently removed a bunch of invasive periwinkle/vinca from under a large maple tree. The area is incredibly root bound, but I’d like to put in a native ground cover to fill the space and prevent the vinca from returning. What would you recommend?
Maple trees have some of the worst surface roots, the worst being the now much-maligned Norway maple. The problem is made worse where soils are thin and there is a lot of subsoil compaction. It is difficult to get things established in such an environment, but the key is to start small, with plugs or even seed. Small bulbs such as scilla, glory-of-the-snow, and even cyclamen might get established there. Another option is to grow things in containers under the tree.
When is the best time to propagate a rambling rose?
Now would be a good time to take cuttings and place them in a sand/compost mix. Keep them moist and protected and they should root over the next few months to be ready for potting next spring for planting the following fall.