Sawtooth Hydrangea Hydrangea serrata

Hardier and more compact than H. macrophylla, this plant was previously listed with lacecap hydrangeas due to its flattened flower heads. However, this is a smaller, more compact plant with smaller leaves and flowers. The flowers have clusters of small florets in the center with a few larger, showy florets toward the outside of each cluster. Flower color varies from blue to pink relative to soil pH. There are also some cultivars with mophead form.

Little pruning is required for this hydrangea and should be done after flowering as it blooms on the previous season's stems.  The annual growth rate is about 18". Weak or winter-damaged stems should be pruned away in early spring.

Although this plant can be grown in sun or partial shade, it is a native of Asia and prefers cool growing conditions and will grow best in light to open shade. In warmer climates, a location protected from hot sun will keep the foliage and flowers from prematurely fading or scorching and it will flower more prolifically with consistent summer watering. 

This hydrangea may be more susceptible to powdery mildew than Hydrangea macrophylla due to its thinner leaves. It also has some susceptibility to bud blight, bacterial wilt, and leaf spot and may occasionally be visited by aphids.

More information on Hydrangea.