Divide perennials to avoid
problems, like dead spots.

Dividing Perennials -- You can still divide most perennials as long as they're not spring-bloomers and their foliage isn't any taller than several inches. Divide them if they are getting crowded (reduced blooms, floppy stems, a dead spot in the middle) or you simply want more plants.

Dividing Perennials

Frost Dates -- Plant warm-season annual flowers, herbs, and vegetables (tomatoes, peppers, basil, marigolds, petunias, and the like) as long as your region's last frost date has passed. (It's as late as May 30 inland at higher elevations.) If you're unsure, give your local garden center a quick call.

Your Region's Last Frost Date

• Those warm-season annuals include plants for containers, pots, windowboxes, and planters. Remove any cool-season flowers you may already have there. Work in a slow-release fertilizer. If there are plants overwintering in the container and you're keeping them, simply work the slow-release fertilizer into the top inch or so of soil.
• After the frost date, plant tender summer bulbs outdoors, including glads, cannas, dahlias, and tuberous begonias.
• You can still take advantage of April's cooler temperatures to plant cool-season crops, including seeds for radishes, peas, sweet peas, lettuces, and other greens, and seedlings for broccoli, cauliflower, and cabbage.
• Wait to plant seeds for corn, green beans, squash, cucumbers, okra, melons, sweet potatoes, and other heat-lovers until 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 frost date.

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 -- You can also continue to plant container-grown trees, shrubs, perennial herbs, groundcovers, and perennial flowers.

Planting Trees and Shrubs

• 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.)
• If you haven't already, reseed a weak lawn this month.

Mulch Matters -- About the time the tulips stop blooming, the soil has warmed up enough that you can apply a layer of mulch on flower beds and around trees and shrubs. It reduces weeds, conserves moisture, and prevents disease. Great stuff!

Mulch Matters

Deadheading 101 -- Deadhead rhododendrons and azaleas by cutting or pinching off spent flower trusses. This will neaten their appearance as well as encourage future blooms. Deadhead other fading flowers too.

Deadheading 101

• Start fertilizing roses, which are heavy feeders. Decide on which plan of attack you want. Some gardenersfeed 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 can also kill butterflies and beneficial insects, so beware.
• For mums, pinch off the last inch or so of the branches until July to assure bushy, well-flowering plants. While you're at it, cut back asters and other tall, floppy, late-summer bloomers by about one-third once they're a foot or so high. They'll be sturdier and flower better.

Pruning Shrubs -- You can prune your rhododendrons and azaleas after they're completely done blooming. After bloom time is finished is the time to prune other spring-blooming shrubs, too.

Pruning Shrubs

Pruning -- Finish up any other pruning this month, with the exception of evergreens, which can be pruned any time from now to late summer.

Pruning

• After that frost date has passed, you can move your houseplants outdoors to a shady spot. It's a good time to repot and fertilize them to ready them for a summer growth spurt.

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