Planning for the garden’s colder months
Washington Post gardening columnist Adrian Higgins answered questions recently in an online chat. Here is an edited excerpt.
Q: We had major drainage work done on our yard, and the regrading and reseeding and covering with straw was done just before two mature maples shed their leaves onto the straw. We usually “vacuum” the leaves up with a mulcher/blower and put them in our compost or use them as mulch, but how do we avoid ruining the new seeding?
A: This is one of the rare moments when a leaf blower (the scourge of autumnal peace) can be used to remove the leaves without disturbing the grass seedlings. Keep it on a low speed (if possible) and keep the nozzle as far above the soil level as you can while still shifting leaves. Be patient and recognize that the maple may keep dropping leaves for another month. Don’t try the vacuum in this circumstance.
Q: What can I pour on the soil of my patio plants to kill pests before bringing them inside for the winter?
A: First, establish that they have pests. The least toxic approach is to spray them with a light horticultural oil before bringing them in, making sure you cover all surfaces, including the undersides of leaves. Follow the directions on the label.
Q: We have a lovely tree peony in the front yard, but after it blooms and drops leaves, it is quite ugly. Can stalks be cut down like a regular peony without losing the plant?
A: No, unlike herbaceous peonies, you cannot simply cut it back to the ground. For one, the buds for next spring are developing. After it blooms next April, you can do some restorative pruning, removing branches that are congested, crossing or weak. But don’t overdo it.
Q: I have two lovely Meyer lemon trees that have winter residence on my heated sun porch. I also have grow lights from dawn til dusk. Generally I wouldn’t fertilize during the winter, but both have growing fruit. Fertilize? What kind?
A: You cut back on fertilizing to induce dormancy, but if you have them growing year-round, that is not quite the same. However, with reduced light levels, I would not feed them heavily and hold back on the nitrogen. You could add a little slow-release citrus food. Watch for mealybugs and scale insects.
Q: We planted an edgeworthia in the front yard and need to prune it. What is the best time of year? We get so many questions about the bush; it’s got a lovely shape, and the winter/early spring display is quite interesting. I just had no idea how much it would grow each year.
A: Edge worthias develop into large and tropical-looking shrubs, but this is a late-winter bloomer, and the buds are ornamental through the winter. This is a shrub to prune in the spring after flowering.
Q: What would cause flowering plants to overgrow but in some cases have limited blooms? I planted cosmos in my west-facing garden that grew to monsterlike proportions (thick stems and lots of leaves) but barely bloomed. Same with the black-eyed Susans. The crape myrtles droop their heavy branches instead of staying upward like their sister in another part of the garden. The soil is compacted sand but amended heavily. What condition would do this and how do I fix it?
A: “Amended heavily” may be the operative words. If the soil is too rich, plants that like lean soil will produce a lot of growth at the expense of flowering. The other issue is that this year we had rainfall measured in feet. Try again, but next year starve the cosmos a little.
Q: What can I do to get rid of the clover and strawberries growing in my grass?
A: Clover is pretty benign, but I admit the wild strawberry is a pain and can take over a lawn. You can remove it with a weeding knife, but it’s laborious work. The bigger problem is that the weeds are invading space left by the retreating turf. It’s really late to do lawn renovation. You could have applied herbicide in August and reseeded a few weeks later. Using herbicide now would impede any seed germination. If you can’t stand it, I would take a thatching rake and slice out the strawberries as much as you can, making sure you rake up all the pieces, and then put down some turf-type tall fescue seeds (assuming you live here or farther north). Do a second seeding in March.
Q: We have a false indigo plant in our front garden. It handles the hot afternoon sun and is also deer-resistant, so it has been great in its location. The plant is beautiful in the spring when it blooms with pale yellow blossoms. However, after blooming this year, the leaves turned black and the plant looked unsightly for the rest of the summer. Is that from all of the rain? New leaves started showing up this fall. Is our area amenable to false indigo? I can’t decide whether to pull it out.
A: False indigo, or baptisia, is a perfect native perennial for the mid-Atlantic, but it grows to the size of a small shrub and is best regarded as a woody plant for combo purposes. Yes, the leaves will look rough after flowering in a really wet year such as this one. There were all sorts of foliar issues this summer. If you can’t stand it, remove them. In the season now upon us, in which perennials take on a ghostly beauty, baptisias provide an incredible dusky black ornament.