A Nimble Weed With a Strong Will

By Scott Aker
Special to The Washington Post
Thursday, March 16, 2006

Q We have nimbleweed taking over the yard. How do we get rid of it?

AThis grassy weed is actually called nimblewill. Whatever its name, it's not easy to get rid of, and if you really want to eradicate it, you will have to rework the turf areas it has infested. There is no selective herbicide for nimblewill. It is a perennial grass, so a pre-emergent herbicide such as those used for crab grass control will have little impact.

Begin by analyzing your lawn. Nimblewill is indicative of saturated soil and shade. You can alleviate the soil saturation by installing drain tiles or by providing better surface drainage by filling in any depressions. It also grows in soil with much lower pH than most grasses will tolerate, so have your soil tested. You may need to add lime to bring the pH to a level that is acceptable for turf grasses. If trees are shading the area heavily, consider removing some of the lower branches to allow in more sunlight.

Before you do anything to correct these soil problems, treat the patches of nimblewill with a nonselective herbicide or a grass herbicide. You will kill the desirable grass along with the nimblewill. Patches of your lawn will be brown until you can get new grass growing. If you have other broad-leaved weeds, however, opt for an herbicide that contains glyphosate instead of a selective herbicide that kills only grasses.

You could do this in early spring, but the better time would be later this year: Treat the nimblewill in late summer so it is dead by early autumn, which is the optimum time to plant grass seed. Loosen the soil as well as you can, fill in any depressions that retain water, and add lime if the soil test results indicate a need for it. Sow the grass seed and be careful to buy seed that is as pure as possible. Cheap seed may contain weed seeds that may turn into major weed problems.

Several areas of my five-year-old crape myrtle are exhibiting splits. This is in addition to the annual shedding of the bark. Like many other crape myrtles in the area, it produced an extraordinary amount of blooms last summer.

I'm not sure what you mean by splits. Splits in the bark are not of concern, especially for trees such as the crape myrtle and paperbark maple whose decorative effect counts on it. But cracks and splits in the wood are serious.

The thin bark of crape myrtle naturally sheds in summer as the tree grows in diameter. Usually it sloughs off in large, clean pieces. Some of these flakes may remain attached to the branches, but this is rare. If the angle between branches is narrow, some bark pieces may accumulate in the crotch.

If you mean that two branches are splitting away from each other where they join, pruning may be required. Crape myrtles have remarkably strong wood that is very flexible and not prone to splitting. However, a heavy load of summer flowers made heavier by rain may cause branches to split if wind is also a factor. If this happens, simply remove the branch carrying the split branches. Cut it back to the branch from which it is growing, and take care to cut above the small ridge of tissue located where the branch meets its parent branch.

Is a dwarf Alberta spruce suitable for growing in a pot on a balcony that gets only limited sunlight?

Dwarf Alberta spruce will tolerate some shade, but over time it will get bare if it does not have sunlight for a substantial part of the day. In your situation, the part of the spruce facing your home will be the first to become thin. Rotating the plant every few months is a good idea if you want to avoid development of a large bald patch in the back of the spruce.

You should know that dwarf Alberta spruce is a mite magnet. Beginning now and periodically throughout the year, check your plants for mite infestation. Tap a branch over a sheet of paper to spot the tiny mites. If you see substantial numbers of them, blast them off your spruce with a strong jet of water from your garden hose. Do this every few days until you can no longer detect the mites.

You might also want to consider other conifers that tolerate shade a bit better. Hinoki false cypress is remarkably resilient as a container conifer in shady locations. Several dwarf types -- Nana and Hage, to name a couple -- do well in containers.

Scott Aker is a horticulturist at the U.S. National Arboretum.

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