Northern & Central Midwest
Start harvesting herbs to preserve by drying, freezing, or in vinegars. Pinch out top growth to keep them from flowering and to intensify the oils. Snip or cut off sprigs of herbs to use in cooking all season. Pinching will also make side buds grow so the plants will be full and shrubby.
Take Houseplants Outdoors
Houseplants and amaryllis can go outdoors now. Harden them off gradually to subject them to sun and wind. Make sure to put amaryllis in a spot in the garden where you will remember to water and fertilize it until the beginning of September when it comes back in.
Protect Squash, Cukes from Pests
Cover emerging squash, cucumbers, and zucchini plants with row covers to prevent squash vine borers from laying eggs on vines and cucumber beetles from transmitting wilt. Remove row covers when plants begin to flower for pollination. Consider planting disease-resistant varieties next year.
Start a Compost Pile
Garden waste should be coming in about now so start a compost pile. Pile a layer of green (vegetable waste, grass clippings), a layer of brown (straw, shredded leaves), and a thin layer of soil. Water in well and wait for the magic to happen. You can turn the pile every few weeks to speed up the magic.
It's time to begin deadheading perennials. Cutting back spring bloomers such as salvia and perennial bachelor button will often push them into a second bloom. Removing the seedheads of daffodils and tulips will help the plant put more energy back into the bulb for next year's blossoms.