Northern & Central Midwest
Watch for Tent Caterpillars
Watch fruit trees, ornamental crab apples, and wild cherries for clusters of small, fuzzy eastern tent caterpillars. Use Bt (Bacillus thuringiensis) when the caterpillars are still quite young. Prune out limbs that become covered with webbing during the day when the caterpillars are inside the web (they come out to feed at night).
Harden Off Frost-Tender Plants
Begin hardening off all frost-tender plants. Vegetables, herbs, perennials, annuals, and summer-flowering bulbs can all be brought outdoors. Expose them gradually to sun and wind until they have hardened, but be ready to scoot them back indoors in case the weather takes a turn for the worst.
Keep an Eye Out for Iris Borer
Watch for iris borer. You will see tunnels in new foliage that look as if they are water-soaked. Pinch the leaf to kill the borer. If borer infestations are bad, look for the biological control made of nematodes that feed on the borers once they enter the tubers. Dig and destroy any diseased tubers.
Plant Warm-Season Crops
Sow seeds of warm-season plants at the end of the month, including beans, okra, pumpkins, sweet corn, and watermelon. Planting only partial rows of beans and sweet corn will allow you to make successive plantings every week or two. Sweet corn should be planted in double rows or blocks for good pollination.
Decide how you will train your strawberries and their runners, and then plant and mulch the plants. Pinch off flowers for this year to strengthen them and cause them to make healthy runners and daughter plants. Keep well watered and watch for aphids and mites.