Culture
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 of most cultivars except white (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 6. 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, most 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). Some newer cultivars have been selected that flower on both old and new wood. Their pruning and flowering can differ from that of the species.
'All Summer Beauty' (1) blooms on both old and new growth and (2) is winter hardy to USDA Zone 5, all of which means that the plants will, within this growing range, reliably flower each year, regardless of winter temperature, and do not need to be covered with burlap in areas such as St. Louis. For added protection, however, plants grown in USDA Zone 5 can be sited in sheltered locations and can be given a good mulch and possibly a burlap wrap for 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.
Noteworthy Characteristics
Hydrangea macrophylla, commonly called big leaf hydrangea, is a deciduous shrub with a rounded habit that, in the St. Louis area, typically grows 3-6’ 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).
The genus name Hydrangea comes from hydor meaning "water" and aggeion meaning "vessel", in reference to the cup-like capsular fruit.
Specific epithet comes from the Greek words makros meaning large and phyllon meaning leaf in reference to plant leaves.
'All Summer Beauty' is a mophead cultivar that grows 3-4' tall and as wide. It typically blooms on both old and new wood (produces flower buds not only in fall but also on new growth in spring and summer). Bloom period is typically June to late September. Each inflorescence is a large globose cyme (mophead) that is primarily covered with showy sterile florets which are blue in acidic soils and rose-pink in alkaline soils. Florets tend to change color as they age. Flowers bloom in mid-summer on old growth with rebloom to frost on new growth. Foliage is a bright medium green.
Problems
Some susceptibility to bud blight, bacterial wilt, leaf spot and mildew. Aphids are occasional visitors.
Uses
Group or mass in the shrub border. Also a good specimen or accent for foundations and other locations near homes or patios. Hedge. Containers.