Blossom time: Crab apples ready for a big show
One of the memory-making pleasures of May is watching plump crabapple buds bursting into bloom, adding clouds of delicate color - and sometimes fragrance - to the landscape, now fully awake and picking up speed.
Considered by many to be the best of the Midwest's spring-flowering trees, crabapple's pink-, carmine- and maroon-colored buds become single, semidouble or double flowers, often in different but equally delightful shades.
A range of heights (from 8 to 30 feet) and habits (rounded, columnar, pyramidal, oval, and weeping) makes it easier to find crabapples in gardens of all sizes. Look for species and newer varieties that offer resistance to apple scab, a fungal disease that commonly affects many older trees.
Crabapples perform best in full sun and well-drained soil, and when their canopies are pruned to increase sunlight penetration and air circulation.
Take some time this month to stop and enjoy crabapples in bloom, and to begin anticipating the pleasures of the red and yellow fruits they will offer this fall.
General garden care
• Plant warm-season annuals, vines, herbs and vegetables after the Chicago area's average last frost date of May 15. Cautious gardeners often wait until Memorial Day before setting out cold-sensitive plants such as tomatoes, peppers, eggplants and squash.
• Continue to plant perennials, ornamental grasses and roses in containers. If plants are root-bound, make four cuts into the bottom of the root ball with a sharp tool, and flare the sections outward when planting.
• Monitor all container plantings for dry soil. On warm, windy days, hanging baskets will require water every day. Terra cotta pots will dry out faster than plastic. Consider incorporating the recommended amount of water-absorbent products into container soil.
• Provide gentle water drip for migrating birds. Birds that migrate in May (warblers, tanagers, orioles and buntings) are attracted to shallow pools and the pinging sound of dripping water.
Flowers
• Stake tall perennials before they reach 6 inches.
• To promote stocky growth, pinch back fall-blooming perennials such as chrysanthemums, asters and tall sedums once a week until the middle of July.
• Continue to direct the growth of perennial vines on their supports.
• Continue to check peonies for botrytis blight or other fungal problems. Peonies affected by botrytis or bud blast last year should be sprayed regularly this year, starting when the plants are 2 to 4 inches tall. Cage or provide support for peony blossoms when the plants are 10 inches tall.
• Let spring bulb foliage yellow before removing it. The leaves use sunlight to manufacture food that is store in the bulb to fuel next year's growth. Braiding daffodil leaves can reduce the number of flowers.
• Spray emerging lily shoots with anti-rodent spray if rabbits have been a problem. Reapply after rainfall.
• Plant summer- and fall-flowering bulbs such as dahlias, peacock orchids (Acidanthera), cannas, tuberous begonias, freesia, gladioli, montbretia, and calla lilies.
Trees and shrubs
•Trees and shrubs can still be planted this month. Plant on a cloudy day, early in the morning, to prevent heat and transplant shock. Water thoroughly and gently at planting time and throughout the first year with 1 inch of water a week. Mulch root zones to conserve moisture.
• Prune spring-flowering shrubs and ornamental trees immediately after they bloom. These include forsythia, viburnum, lilac, small magnolias, rhododendron and azalea. Prune to the ground old canes of forsythia and lilac.
• Fertilize roses with a liquid 20-20-20 solution when flower buds are set.
• Monitor roses for insects and disease. Check daily for black spot, especially in wet weather. Make sure leaves are dry before removing infected leaves, and spraying with an approved fungicide.
Lawns
• Mow lawn to 2 to 2 1/2 inches, removing one-third or less of the leaf blades. Leave grass clippings on the lawn to return nutrients to the soil, or add them to a compost pile.
• If you are applying grass seed, do not use a pre-emergent weed killer in the same area.
• If necessary, fertilize lawn in mid-May. Late fall is a preferable time to fertilize.
• Monitor for weeds and hand pull or spot treat accordingly.
Fruits and veggies
• Plant corn, snap beans, and summer squash in mid-May.
• Thin carrots, beets and late lettuce.
• Harvest green onions, lettuce, and radishes.
• Harvest mature asparagus and rhubarb.
Houseplants
• Begin to harden off warm-season transplants, moving them into a cold frame or protected area.
• Gradually move houseplants outside to protected areas. Large houseplants in plastic pots should be slipped into heavier pots to prevent them from tipping over in wind. Guard against overexposure to afternoon sun.
• Overwintered tender annuals or tropicals (hibiscus, gardenia, geranium) may be pruned, fertilized and taken outside once night temperatures are 40 degrees.
Denise Corkery is a horticultural writer for the Chicago Botanic Garden.