Big-leaved hydrangeas are valued for their showy flowers. However, in Zone 5 and lower, the flower buds of these small shrubs from Japan are generally not hardy in cold winters. This type of hydrangea sets its flower buds on the previous year’s growth (old wood), so they are more susceptible to freeze damage. In recent years, some cultivated varieties have been developed that are somewhat hardier. But even the new cultivars will do better if placed in a protected location and are covered with snow throughout the winter.
Blue flowers are one of the plant’s appeals, but big-leaved hydrangeas only have blue flowers when planted in acid soils. In alkaline soils, such as those in most of the Chicago region and the Great Plains, the flowers will be pink. Flower clusters will vary by cultivar. Some cultivars have large clusters of mostly showy (sterile) flowers, with a few non-showy (fertile) flowers in the interior of the cluster. These are often referred to as mopheads. Other cultivars have lacecap-type clusters. These usually feature a center of non-showy (fertile) flowers surrounded by an outer ring of the showy (sterile) flowers.
The species and older cultivars bloom only on old wood. In zone 5, the plant often dies to the ground in winter so there is no old wood, and therefore, no flowers. Many newer cultivars will bloom on old and new wood (current season’s growth). Thus, if the old wood dies back, the plant can still bloom on the new wood.
- Family (English) Hydrangea
- Family (botanic) Hydrangeaceae
- Tree or plant type Shrub
- Foliage Deciduous (seasonally loses leaves)
- Native locale Non-native
- Size range Low-growing shrub (under 3 feet), Small shrub (3-5 feet)
- Light exposure Partial sun / shade (4-6 hrs light daily)
- Hardiness zones Zone 5 (Northern Illinois), Zone 6 (City of Chicago), Zone 7, Zone 8, Zone 9
- Soil preference Acid soil, Moist, well-drained soil
- Tolerances Alkaline soil
- Season of interest early summer, midsummer, late summer, early fall, mid fall, late fall
- Flower color and fragrance Blue, Pink
- Shape or form Multi-stemmed, Round
- Growth rate Fast