The shrubs and vines that belong to the hydrangea genus are popular deciduous flowering plants that bloom in large, attractive flower clusters from mid-summer through fall. There are several different species of hydrangeas, many of which have white, pink, red or blue flowers that can change color depending on the soil pH and presence of aluminum in the soil. In acidic soils, the hydrangeas can absorb the aluminum traces, turning the blossoms blue. Hydrangeas can grow in a wide range of mild or temperate climates, except for the regions with the coldest winters. Mophead and Lacecap hydrangeas (Hydrangea macrophylla) and oakleaf hydrangeas (H. quercifolia) are hardy down to USDA Zone 5b, tolerating winter temperatures down to -15 degrees Fahrenheit, while Annabelle (H. arborescens 'Annabelle') and PeeGee family hydrangeas (H. paniculata) are hardy down to Zone 3a, withstanding temperatures as cold as -40 degrees.
Plant your hydrangeas in spring or fall. If you live in a hotter climate, choose a planting location that has partial sunlight exposure with some shade in the afternoon. Otherwise, plant your hydrangea shrubs in full sunlight and in well-draining soil.
Dig a planting hole that's the same depth as three times the width of the hydrangea's root ball. Mix into the displaced soil some organic compost, if your soil is heavy or nutrient poor.
Remove the hydrangea's root ball from the nursery container and set it into the planting hole. Backfill the planting hole with soil about halfway, water thoroughly to remove air pockets around the roots, and then fill the planting hole the rest of the way. Water deeply and thoroughly again.
Spread a 2- to 4-inch-thick layer of organic mulch on the ground around the base of your hydrangea shrub, keeping the mulch about 2 inches away from the trunk.