How to Fertilize saw-toothed hydrangea?
Hydrangea shrub feed every four weeks spring through early summer

saw-toothed hydrangea · Hydrangea serrata
Grow in moist but well-drained, humus rich soil, in a lightly shaded spot with shelter from cold, drying winds. Mulch annually in spring. Soil additives may be required to maintain specific flower colours. See shrubby hydrangea cultivation for more detailed advice
Hydrangea shrub feed every four weeks spring through early summer