Most hydrangea questions are really pruning questions, and the answer depends on the type. This profile follows Iowa State University Extension's hydrangea pruning guidance: smooth and panicle hydrangeas bloom on new growth, while bigleaf hydrangeas differ by cultivar. The page does not give planting-site or watering numbers, so check your plant's label and your growing zone for those.
Hydrangea at a glance
| Type | Flower |
|---|---|
| Season | Perennial |
| Sun | Part shade |
| Plant spacing | 60 in |
| Row spacing | 60 in |
| Per square foot | 1 |
| Seed depth | At surface |
| Days to maturity | Blooms early to late summer, depending on type |
| How to start | Prune smooth hydrangea back to the ground in March or early April. |
| Water | 1 in per week |
These are the same numbers our plant spacing, square foot and harvest date calculators use. See every crop in the plant database.
When to plant hydrangea
Prune smooth hydrangea back to the ground in March or early April. For panicle hydrangea, reduce size by selectively removing a few branches in March or early April; rejuvenate large, old shrubs in late winter or early spring by removing several of the largest stems near ground level. For bigleaf hydrangea, wait until shrubs begin leafing out, then remove all dead wood.
How to plant hydrangea
- Know your type. Smooth and panicle hydrangeas bloom on new growth. Older bigleaf cultivars such as 'Forever Pink' and 'Nikko Blue' bloom only on the previous year's growth; newer bigleaf cultivars such as Endless Summer and 'Blushing Bride' bloom on both previous and current year's growth.
- Check your hardiness. Iowa State notes older bigleaf cultivars often die back to the ground over Iowa winters and bloom poorly.
- Set flower color for bigleaf types with soil pH: acidic soil produces blue flowers, alkaline soil pink.
Caring for hydrangea
After a mild winter, newer bigleaf cultivars bloom in early summer on old wood and late summer on new wood. After a cold winter they die back to ground level and bloom in late summer on new growth. For maximum bloom, delay pruning bigleaf hydrangeas until leafing out so you can see what is alive.
Test your soil before trying to change flower color; the mulch calculator and garden watering calculator help with the basics of establishing any shrub.
Companion plants
| Grow nearby | Shade-tolerant perennials such as hosta and hellebore beneath the shrub |
|---|---|
| Keep apart | Heavy pruning of bigleaf hydrangeas before you can tell which stems are alive |
Pair with hostas and hellebores; both are in our plant profiles. Check other pairings with the companion plant finder.
Common problems
| Problem | What you see | What to do |
|---|---|---|
| No flowers on bigleaf hydrangea | Healthy foliage but no blooms | Often winter dieback of old-wood buds or pruning at the wrong time. Wait until leaf-out before pruning. |
| Flower color not what you expected | Pink instead of blue, or the reverse | Bigleaf flower color depends on soil pH: acidic soil produces blue flowers and alkaline soil pink. |
| Dieback after cold winters | Dead stems back to ground level | Common with older bigleaf cultivars in cold areas; newer cultivars still bloom on new growth after cold winters. |
Not sure what you are looking at? The plant problem identifier ranks likely causes from the symptoms you see.
When and how to harvest
Hydrangeas are ornamental shrubs and are not harvested. Check plant toxicity before planting around pets; see our pet-safe plants guide.
Plan your hydrangea
- Plant spacing calculator: how many plants fit your bed
- Planting calendar: sowing and transplant dates for your frost dates
- Frost dates by ZIP code: your last spring and first fall frost
- Harvest date calculator: when your crop will be ready
Frequently asked questions
How far apart should I plant hydrangeas?
Space hydrangeas 60 inches apart in rows 60 inches apart. In a square foot garden, plant 1 per square foot.
How deep do I plant hydrangea shrubs?
Plant at the same depth as the nursery container; check your plant's label for site needs.
How long do hydrangeas take to grow?
Smooth hydrangea can be cut to the ground in March or early April; bigleaf types bloom early to late summer depending on cultivar and winter.
How much water do hydrangeas need?
About 1 inch of water a week, from rain and watering combined. Keep newly planted hydrangeas well watered while they establish; this page's source focuses on pruning.
When do I prune hydrangeas?
Smooth and panicle types in March or early April; bigleaf types once they begin leafing out.
Why won't my bigleaf hydrangea bloom?
Older cultivars bloom only on previous year's growth, which winter often kills.
How do I change hydrangea color?
For bigleaf types, acidic soil produces blue flowers and alkaline soil pink.