How to Fertilize woolly-leaved hydrangea?
Add slow-release shrub fertilizer once yearly at early spring bud break

woolly-leaved hydrangea · Hydrangea heteromalla
Grow in moist but well-drained, humus rich soil, with shelter from cold, drying winds and late frosts. This species will tolerate full sun if the soil is kept consistently moist. Mulch annually in spring. See shrubby hydrangea cultivation for more detailed advice
Add slow-release shrub fertilizer once yearly at early spring bud break