Silverleaf Hydrangea

Size, growth and what to expect

No source rates its speed. Our growth estimator gives it the fast class, since its close relative, smooth hydrangea, grows rapidly. It makes an open, rounded shrub 3 to 6 feet tall and 4 to 6 feet wide, with many unbranched stems and shreddy bark.

Domed heads 3 to 6 inches across open from May into July. Each holds 200 to 500 tiny fertile flowers ringed by a few large white sterile ones. Bees, butterflies and other pollinators visit them. In fall the dying leaves curl up and show their white undersides.

It grows wild only where North Carolina, South Carolina, Georgia and Tennessee meet, and it is often common on road banks there. Its home is moist deciduous forests, ravines, rocky slopes and cliffs, from about 650 to 3,900 feet up.

How to grow Silverleaf Hydrangea

Silverleaf hydrangea wants part shade to full shade and a moist, rich, acid soil that drains well. The more sun it gets, the more water it needs. It takes heat and drought less well than smooth hydrangea. Plant it 3 feet from a wall and set plants 4 feet apart in a mass. Its size lets it go within 15 feet of overhead wires.

Saplings ship bare-root or potted. Plant them dormant, from leaf fall until bud swell, in a hole wider than the roots and no deeper. Set the crown at the soil line, put the native soil back in, and keep a mulch of leaves over the roots, clear of the stems. The seed is dust-fine and needs no chilling. Sow it indoors on the surface of moist seed mix, uncovered, under lights. Seedlings come up in one to two weeks.

Water weekly through the first two summers and in every dry spell after that. It flowers on new wood, so cut the stems back close to the ground in late winter to renew the plant. Where deer visit, cage young plants for the first two winters.

Each small inner flower carries both male and female parts, while the large white outer flowers are sterile. Silverleaf hydrangea's close relative, smooth hydrangea, sets no viable seed with its own pollen, so plant two or more seedlings from different parents if you want seed. Dry, ribbed capsules follow in October and November and hold seed as fine as dust.