Select flowers that tolerate air-drying without losing their petals in the drying process. This mostly excludes fully opened flowers and flowers with fleshy stems. Roses (Rosa spp.), peonies (Paeonia spp.) and hydrangeas (Hydrangea spp.) are among the many flowers that are well suited for air-drying. Roses thrive in U.S. Department of Agriculture plant hardiness zones 2b through 10b; peonies grow in USDA zones 3 through 8; hydrangeas are hardy in USDA zones 3 through 9.
Cut flowers from the stems in late afternoon when there is no moisture on the petals or leaves. Use bypass pruners to cut through the stems; cut the stems back to the point of intersection with a branch or back to the ground, depending on the type and size of the stems.
Strip the flower stems of leaves that get in the way when the stems are gathered into bunches. You can pick the leaves off the stems without any tools. Clip the stem length, if desired, but don't cut the stems shorter than 8 inches.
Gather the flowers into small bunches. Stagger the flowers as needed to prevent the flower heads from touching others in the bunch. Tie the bunches together with natural twine or rubber bands.
Cover any windows in your garden shed with blackout curtains or black plastic to make the shed as dark as possible. Hold a trash bag up to the window and staple it in place around the sill. The dark environment helps preserve flower color.
Install hooks in the ceiling rafters to provide a place to hang the flower bunches. Screw hooks, wood screws and nails all work well for hanging bunches. If you can spare the floor space, you can use a wooden drying rack, which has several horizontal bars at different heights, to hang and dry the flowers.
Hang the flower bunches upside down from the nails, screws or hooks from the tie or rubber band used to hold the bunch together. If hanging directly on the hook would make the stems contact with the ceiling, cut a second piece of twine and tie it to the string or rubber band to create a loop. Slip the looped twine over the nail or hook.
Add an oscillating fan to the garden shed to circulate air around the flowers. You don't need to point the fan directly at the flowers.
Check the flowers frequently after about one week and remove the bunches when the flowers are completely dry. Drying can take between one and three weeks, depending on the size and density of the flower heads. Hydrangeas that have small flowers spread across a wide flower head are more likely to dry quickly than peonies, which have dense clusters of petals in a large flower head.
Store the dried flowers in airtight bags or storage containers to protect them from insects and rodents. Alternatively, make use of the flowers right away. Use the flowers in dried flower arrangements or tie attractive ribbons around the bundles and hang them in your home.