Ohio's warm summers and cold winters provide an adequate climate to raise many hydrangeas, although winter protection is needed for some that are less hardy. USDA plant hardiness zones 5 and 6 encompass the Buckeye State, which means varieties such as bigleaf, lacecap, mountain, panicle and smooth can be grown. New varieties featuring different and continuous bloom colors are also introduced annually, contributing to hydrangeas' popularity in Ohio.
Pick a plot that ideally receives full morning sun and some afternoon shade, like the north side of a landscape, or a space that is mostly sunny, such as on hilltops in southern or northeast Ohio.
Provide well drained soil and enough space for each plant to grow to about 4 feet in height and width. Add pine bark mulch to soil that does not drain well, like soil with a high concentration of clay, often found in northwest Ohio. Avoid planting hydrangeas in swampy areas or places that flood, such as flatland along the banks of the Blanchard River in Findlay.
Plant hydrangeas in early summer when they are in bloom, or late fall, in November or December, after the plant has shed all its leaves and is dormant and before the ground freezes. Avoid planting them in July or August, the hottest Ohio months. Dig a hole with a spade and plant them at the same soil depth as they grew in their containers.
Water hydrangeas well and consistently, but do not overwater the plants. The soil should be slightly moist but not soggy.
Apply a balanced, slow-release fertilizer, such as 10-10-10, or organic manure to the plants once or twice annually during the growing season. Avoid fertilizing the plants as their growth wanes, usually in early fall in Ohio.
Change the color of your pink or blue hydrangeas, if you wish. Add lime to acidic soil to turn blue flowers pink or aluminum sulfate to alkaline soil to turn pink flowers blue; soil in the western half of the state is generally more alkaline while soil in the eastern half is usually more acidic.
Do not cut the stems off of bigleaf hydrangeas unless the plants are growing too big, and then cut them back with pruners in mid-summer. Remove the dead stems from mophead and lacecap hydrangeas annually. Remove about a third of the older stems to the ground each summer on plants that are at least five years old. Cut off dead blooms at any time.
Prune paniculata and Annabelle plants that bloom on new wood down to within a few inches of the ground in the fall or winter in Ohio.
Protect more sensitive hydrangea varieties, such as mopheads and lacecaps, from Ohio's harsh winters by covering buds that usually form at the tips, all winter. Surround plants with chicken wire, fill leaves or straw around the plants and cover them with burlap tied to the base of the cage, or simply cover the plants with leaves and burlap that is tied with twine to the base of the plant.