When to Plant Hydrangeas

Fall: the best window

Hydrangeas are sold in bloom in late spring and summer, which is why most get planted then. But extension services agree that fall and early spring are better. Clemson names spring and fall as the best seasons, and Alabama Extension goes further, calling fall the best planting time because the shrub has several months to grow roots before it flowers.

Fall works because the soil stays warm after the air cools. Illinois Extension explains that new roots keep growing in warm fall soil while the plant above ground is slowing down, so a fall-planted shrub starts its first summer with a head start on one planted in spring. Its rule for shrubs and perennials is to plant about six weeks before the first frost and not much closer. The fall dates for your zone above count back six to eight weeks from your average first frost.

A few practical points for fall planting:

• Water until the ground freezes. Water well at planting and whenever the soil dries, then stop after the first hard freeze (Illinois).
• Don’t fertilize. Illinois advises against fall feeding, which pushes soft growth that winter damages.
• Mulch 2 to 3 inches once nights approach freezing, keeping it off the stems.

Spring: a close second

Early spring is Alabama’s next-best planting time after fall, and it gives a hydrangea the whole growing season to establish. Oregon State considers spring through early fall a good planting season as long as you avoid hot weather.

Spring-planted hydrangeas face their first summer with a small root system, so expect to water regularly, about an inch a week, through the summer. Bigleaf hydrangeas bought in spring may already carry flower buds; plant them where late frosts are less likely to hit, such as an east- or north-facing site (Alabama).

Summer planting

Container hydrangeas can go in the ground any time the soil isn’t frozen, but summer is the hardest season. Clemson warns that the large leaves lose moisture fast and plants can suffer if set out in hot weather. If you do plant in summer:

• Water deeply right away and keep the soil evenly moist; Tennessee stresses consistent watering through the whole first year.
• Give afternoon shade, which most hydrangeas need anyway.
• Expect some midday wilting on hot days even in moist soil; Tennessee notes this is normal for bigleaf hydrangeas.

Timing by region

• Cold North (zones 3-5): Panicle and smooth hydrangeas are the reliable choices. Fall plantings need to be in the ground six to eight weeks before the first frost, which comes early here, so don’t wait for cool October days.
• Mid-Atlantic, Midwest and upper South (zones 6-7): Early fall is ideal, with spring a good alternative.
• Southeast and Gulf Coast (zones 8-9): Fall planting lets roots establish before the long, hot summer. UF/IFAS rates bigleaf (French) hydrangeas as best for North and Central Florida, where winters are still cool.
• Pacific Northwest: Spring through early fall, avoiding hot spells (Oregon State).

When to prune is a separate question

Planting time and pruning time are often confused. Bigleaf and oakleaf hydrangeas set next year’s buds in late summer, so prune them right after flowering and before August 1. Panicle and smooth hydrangeas are pruned in late winter or early spring. See how to grow hydrangeas for the details.