Culture
Best grown in rich, medium moisture, well-drained soils in part shade. Tolerates full sun only if grown with consistently moist soils. Bloom occurs on old wood. Prune after flowering by cutting back flowering stems to a pair of healthy buds. Prune out weak or winter-damaged stems in early spring.
'Preziosa' has better winter hardiness than many of the hydrangeas and is often rated as hardy to USDA Zone 5. However, it is best to grow it with winter protection (e.g., mulch and burlap wrap) in Zones 5 and 6A where plants could still lose significant numbers of flower buds or die to the ground in harsh winters, thus respectively impairing or totally destroying the bloom for the coming year.
Noteworthy Characteristics
Hydrangea is a genus of 80 or more species of deciduous and evergreen shrubs, climbers and rarely trees from East Asia and North and South America. Many have very showy flowers.
The genus name Hydrangea comes from hydor meaning "water" and aggeion meaning "vessel", in reference to the cup-like capsular fruit.
'Preziosa' is a mophead-type hydrangea which is varyingly listed as a cultivar of H. serrata or as a cultivar of H. macrophylla or as a hybrid between the two. It is a compact deciduous shrub with a rounded habit which typically grows to 3-4' tall and as wide unless damaged by harsh winters or pruned smaller. Features small mophead-like panicles (3-4") in which the showy sterile florets progress through several different color changes (white to pink to reddish-purple) over a long summer to fall period. Serrate leaves emerge purple-tinted, mature to green and again acquire red to purple tints in fall. Dark maroon stems.
Problems
No serious insect or disease problems. Some susceptibility to bud blight, bacterial wilt, leaf spot and mildew. Aphids are occasional visitors. Winter hardiness in the St. Louis area can be a significant problem for some hybrids.
Uses
Group or mass in a sheltered location in the shrub border. Also a good specimen or accent for protected locations near homes or patios.