Plant warm-season annuals, such as marigolds and impatiens, after your region's last average frost date. That's late April to May in the southern Midwest and around the middle of the month in the northern Midwest. You'll have your favorites, of course, but try something new this year, too. Pictured: A double petunia.
Plant summer-blooming corms and tubers such as gladiolus corms, canna rhizomes, tuberous begonias and other summer bulbs.
Plant or transplant perennial edibles now, including strawberries, raspberries, rhubarb and asparagus.
Continue to plant trees, shrubs and roses. But don't plant bare-root types after the middle to end of the month, except in the northern part of Zone 4. They need cool, wet weather to take off.
Divide and transplant most summer- and fall-blooming perennials now. They'll have plenty of time to get established by bloom time. Wait to divide spring bloomers until fall.
Dig new beds and borders as long as the soil isn't too wet; you can ruin the texture of the soil by creating muddy clumps and clods. If the soil is moist enough for you to form a ball in your hand, it's probably too wet for digging. If your soil isn't very good (too much clay or sand, for instance), create raised beds that you can fill with commercial topsoil. They're the smartest solution to problem soil.
Apply a preemergent weed killer, such as Preen, to your flowerbeds and borders when the bright yellow forsythia bush is blooming. This prevents seeds from germinating and dramatically cuts down on weeding chores later in the season.
Fertilize containers regularly. All that watering flushes out many nutrients. For best results, use a special bloom-boosting fertilizer on flowering plants.
Mulch with wood chips and other weed-suppressing materials this month in the southern Midwest, now that the soil has warmed. Wait until June in the northern Midwest.
Don't cut off the browning foliage of spring bulbs, such as tulips and daffodils, just yet. They need to "ripen" on the plant and replenish the bulb for next year. Remove the foliage once it pulls away with very little resistance.