Dozens of hydrangea varieties exist, and their flowers are often dried and used for dramatic bouquets. Hydrangea bushes, given enough light and moisture, are marvelously simple shrubs to maintain and transplant. Transferring hydrangeas to a new location is a simple task. Although some varieties set flowers on the previous year's growth, many flower on the current year's growth. The way they bloom provides the clue as to whether to move them after they bloom or when they go dormant in the fall.
Choose a spot for your hydrangea where it will receive full sun in the morning. If you live in the northern U.S., dappled afternoon sun is good too. Its new home should be in fertile, well-drained soil. Never plant your hydrangea under a tree; even if it gets enough sun, its delicate roots can't compete with tree roots for water and nutrients.
Prune back dormant arborescens (Annabelle and relatives) and paniculata (pee gee family) hydrangeas down to 6 to 8 inches tall. Macrophylla (lacecaps and moptops) and Oakleaf types will lose a season of bloom if pruned after July. So, plan ahead and prune them back about 1/3 just after they bloom---to be ready for transfer in the fall or, if necessary, the following spring.
Dig around the drip line with a spade and work down under the root ball with a fork. Try to lift the entire root ball by working around and under with the fork---hydrangeas have very dense root balls of very fine roots. Transport the heavy root ball in a wheelbarrow or cart to keep it from damage.
Dig a receiving hole the same depth as the root ball and two to three times as wide. Line the hole with compost or humus only if the soil lacks fertility. Set the root ball in the hole and fill the hole halfway with soil.
Water gently but deeply to drive out any air bubbles and settle the root ball into its new home. Check to make sure that the crown of the hydrangea sits at the same level in the soil as it did previously, and finish filling the hole with soil. Water the shrub well.