When to Plant Hydrangeas
Popular flowering shrub producing large, showy bloom clusters. Flower color changes with soil pH — blue in acid, pink in alkaline.
The Short Answer
How to Grow Hydrangeas
Hydrangea flower color is determined by soil pH, but only for certain varieties: blue flowers in acidic soil (pH below 5.5), pink in alkaline (pH above 6.5), and purple in between. White-flowered varieties don't change regardless of pH. The most common hydrangea frustration is 'my plant doesn't bloom' — usually caused by pruning at the wrong time. Old-wood bloomers (macrophylla) should only be pruned immediately after flowering; new-wood bloomers (paniculata, arborescens) can be pruned in late winter. Endless Summer was the breakthrough reblooming variety that blooms on both old and new wood.
Transplanting
Move seedlings outside 0 weeks after your last frost date, once soil temperatures reach 50°F. Harden off seedlings for 7 days before transplanting by gradually exposing them to outdoor conditions.
Fall Planting
Hydrangeas are planted in fall, 6 weeks before your average first frost date. , 60" apart.
Growing Tips
Blue flowers: add sulfur to lower pH. Pink flowers: add lime to raise pH. White varieties don't change color. Prune according to variety — some bloom on old wood, some on new.
Companion Planting
Good companions:
Hydrangeas Planting Dates by State
Click your state for hydrangeas planting dates specific to your location:
Last reviewed: March 29, 2026