The Endless Summer Collection of hydrangeas were originally bred by Dr. Michael Dirr of Minnesota. These are the only hydrangeas that bloom on both old and new wood, giving them the ability to rebloom and to provide the gardener with a longer flowering season. Although Endless Summer hydrangea is hardy to USDA zone 4, it will require winter protection in areas with cold winters.
Plant your Endless Summer hydrangea in an area that receives full sun in the morning and dappled or light shade in the afternoon. The farther north you live, the more sunlight the Endless Summer hydrangea can tolerate.
Water the Endless Summer hydrangea deeply and slowly twice a week. A soaker hose works well for this. The soil should be completely saturated at each irrigation and allowed to dry to within 1 inch of the surface prior to watering again. If the leaves wilt or droop, water the plant.
Place a 3-inch layer of mulch around the base of the hydrangea, 2 inches away from the bark and spread in a 3-foot radius around the plant. Mulch helps keep the soil moist and discourages weeds.
Fertilize the Endless Summer hydrangea with a slow-release 10-30-10 formula twice a year, in the spring and the summer. Apply the fertilizer at the rate suggested on the product label. In USDA zone 4, do not fertilize after mid-August.
Remove dead flowers, using the pruning shears, frequently throughout the growing season, as this encourages the plant to produce new blooms. Unlike other hydrangea varieties, Endless Summer does not require pruning. If you need to prune to keep it to a desired shape or size, do so in the spring.
Overwinter your hydrangea in USDA zone 4 and 5 by keeping the soil moist until the ground freezes. Pour a 4-inch layer of mulch or leaves over the Endless Summer plant after the plant has gone fully dormant, generally mid-to-late November. Do not remove the mulch until the soil has thawed.