Some advice from Charlotte Kidd of Radnor, Pa., who writes about Mid-Atlantic gardening for the National Gardening Association:

• Despite some residual winter chill, mosquitoes are starting to buzz around the gardens. We tend to think of emptying water from pots, buckets, and saucers. Some mosquito types that spread West Nile virus breed in the wet leaves in roof gutters. Clean your house gutters and encourage neighbors to do the same.
• There are several ways to stop wriggling mosquito larvae from infesting rainbarrel water. Some gardeners recommend keeping a layer of vegetable oil on top of the water. Others add the biological control Bt-israelensis (Bt-i), which is in mosquito dunks that last 30 days. One dunk treats 100 feet of water; it can be broken in half. Some rainbarrel plans include instructions to place a piece of wire mesh over open water.
• Your garden doesn't always need new mulch. Two or three inches are enough to suppress weeds and retain moisture. If last season's mulch is sufficient in your garden beds, fluff it up. By that I mean use a hoe or cultivator to break the mulch crust. Chop it and mix it, uprooting any small, sprouting weeds in the process. Fluffing will allow water to reach the soil and roots beneath the mulch layer.
• For broader, shorter plants, clip 2 or 3 inches off the tops of Phlox paniculata and Asters. Cut the stem just above the connection where leaf meets stem meets the node. For a longer blooming stand of summer Phlox, clip the front half of cluster lower than stems in the rear. Be sure to prune off the dead Phlox flowers to encourage more successive flowering.
• (I would add, cut back your sedum, too, and your cone flowers. This keeps the blooms from flopping over and, in the case of sedum, breaking off. You should also be pinching back your mums until at least the Fourth of July.)