Botanical: Hydrangea macrophylla 'Merritt's Supreme'
Common: Bigleaf Hydrangea
Family: Hydrangeaceae (hydrangea Family)
General Characteristics: Hydrangea macrophylla, commonly called big leaf hydrangea, is a deciduous shrub with a rounded habit that typically grows 3-4' tall and as wide unless damaged by harsh winters or pruned smaller. It generally features serrate, obovate to elliptic, dark green leaves (4-8" long) and large clusters of long-blooming summer flowers in either lacecap form (flattened flower clusters of small fertile florets with scattered showy sterile florets often forming a marginal ring) or mophead form (globose flower clusters of mostly showy sterile florets).
Tip: Best grown in rich, medium moisture, well-drained soils in part shade. Tolerates full sun only if grown in consistently moist soils. Soil pH affects the flower color (blue in highly acidic soils and lilac to pink in slightly acidic to alkaline soils). Add aluminum sulfate to the soil to make the flowers bluer or add lime to the soil to make the flowers pinker. Begin soil treatments well in advance of flowering, as in late autumn or early spring. Plants generally need little pruning. If needed, prune immediately after flowering by cutting back flowering stems to a pair of healthy buds. Prune out weak or winter-damaged stems in late winter/early spring. Best to mulch plants year-round with 3" of shredded bark, peat or compost. Winter hardy to USDA Zone 5. For added protection, however, plants grown in USDA Zone 5 should be sited in sheltered locations and given additional winter protection, as needed, for the purposes of minimizing the risk of loss of significant numbers of flower buds or possible die-back to the ground in an extremely harsh winter. A burlap wrap of stems or circle of chicken wire filled with leaves or straw to 8-12" are time-consuming and visually unattractive landscape options, but can be effective. Regardless of protective measures taken, bigleaf hydrangeas simply will not bloom (or will bloom poorly) in some years because of a variety of winter occurrences beyond the control of the gardener (e.g. low temperatures, sudden wide temperature fluctuations, icy conditions, late frosts).
This hydrangea grows best in fertile, well-drained soils. They are not very drought tolerant, and should be watered regularly during dry periods. The hydrangea should be placed in partial shade in areas that have overly hot summers.
Garden Use: Group or mass in a sheltered location of the shrub border. Great cut flower. Also a good specimen or accent for protected locations near homes or patios.