Divide perennials to avoid
problems, like dead spots.

Dividing Perennials -- Divide most perennials once they've sent up significant foliage at least a couple of inches tall. Divide them if they are getting crowded (reduced blooms, floppy stems, a dead spot in the middle) or you simply want more plants. Wait to divide spring-blooming perennials until after they've bloomed.

Dividing Perennials

Deadheading 101 -- Deadhead spent flowerheads on spring-blooming bulbs to direct their energy back to their roots so they can build vigor for next year.

Deadheading 101

Planting Bare-Root Trees, Shrubs, and Roses -- Continue to plant bare-root trees and shrubs as well as bare-root roses.

Planting Trees and Shrubs

Planting a Bare-Root Rose

Planting Trees and Shrubs -- Continue to plant container-grown trees, shrubs, perennial herbs, ground covers, and perennial flowers as long as you're no more than a month away from your last average frost date.

Planting Trees and Shrubs

• Plant pots, windowboxes, and containers with cool-season flowers that can withstand frost and even snow. Pansies are a favorite. Or, tuck in pots of purchased forced spring-bulbs, such as tulips or daffodils, which are available at supermarkets and garden centers now, to brighten these spots.

Frost Maps -- In the coldest northern regions and at higher elevations, you can still plant cool-season crops, such as seeds or seedlings of radishes, peas, sweet peas, lettuces, and greens. Plant seedlings of broccoli, cauliflower, and cabbages. In warmer regions and lower elevations, the last average frost date is this month. That means you can go ahead and plant warm-season annuals (tomatoes, peppers, basil, marigolds, petunias, and the like) since all danger of frost has passed. If you're in doubt, call a local garden center. But we do mean local. Frosts can come at vastly different times depending on elevation and exposure.

Frost Maps

After the Thaw -- Plant seeds for corn, green beans, squash, cucumbers, and other heat-lovers only once the soil has warmed to 60 degrees F. That's warm enough for you to walk on it comfortably barefoot, and is usually two weeks after your region's last average frost date.

Region's Last Frost Date

What to Plant -- Plant potatoes and perennial vegetables, such as rhubarb, strawberries, and asparagus this month.

Strawberries

Pruning Roses -- If you haven't already, prune roses once signs of growth are well underway, that is, the red leaf buds have started to swell and just barely started to unfurl.

Pruning Roses

• Start fertilizing roses, which are heavy feeders. Decide on which plan of attack you want. Some gardeners feed every two weeks until August with a liquid fertilizer. However, a lower-maintenance approach is to work a slow-release fertilizer (or compost) in around the shrub according to package directions, usually every 6 weeks or so. Some rose fertilizers include a systemic pesticide, so you can feed and prevent pests at the same time. However, these pesticides also can kill butterflies and beneficial insects, so beware.
• Prune evergreens any time from now until late summer. (Don't prune later than that or you'll prompt new, tender growth that will get zapped by winter's cold.)

Pruning -- Finish up the rest of your pruning this month with the exception of spring-blooming trees and shrubs. You can prune them immediately after they're done flowering.

Pruning

• When it comes time to mow your lawn, do so regularly and at the right height. It's the best thing you can do to control weeds and keep grass thick and healthy. Now, during cool weather, mow cool-season lawns such as bluegrass, ryegrasses, or fescues at 2 inches or so. Raise the mower blade to 3 inches once temperatures hit the 90s F. Mow warm-season grasses such as Bermuda, St. Augustine, and zoysia at approximately 2 inches all season long.
• April is a good time to aerate your lawn. Most lawns should be aerated every two or three years to alleviate compaction and reduce thatch. You'll need to rent a machine that takes out plugs of soil or have a lawn service do it. (As an alternative, fall is also a good time.)
• Early this month, if desired, apply a pre-emergent weed killer to beds and borders. It will greatly reduce weeds later on. However, it works by preventing seeds from germinating, so don't apply anywhere you're planting seeds.
• For the greenest, lushest lawn, apply another application of fertilizer to your lawn late this month or early next.
• Clear out debris and muck from the bottom of the water garden and add it to your compost heap. Start feeding fish again when water temperatures hit 50 degrees F or they're active and eagerly eat the food.

Composting 101 -- Your compost heap can probably use a little spring TLC. Open it up or tear it apart to get to the completely composted "black gold" down at the bottom and work it into the soil as you plant. Make sure remaining material is nicely chopped up or in manageable pieces (try running over softer stuff with a lawn mower equipped with a collection bag).

Composting 101