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Get the iPhone app Browse the guideMountain Hydrangea
Hydrangea serrata
Also called Tea of Heaven, Sawtooth Hydrangea
About Mountain Hydrangea
This hardy shrub produces delicate lacecap flowers that pollinators love. The flower color shifts toward blue in acidic soil and pink in alkaline soil. It handles cold winters better than bigleaf hydrangea.
- Type
- Deciduous shrub
- Height
- 2–4 ft
- Spread
- 2–4 ft
- Sun
- Morning sun and afternoon shade
- Water
- Keep soil moist but not soggy
- Soil
- Rich, moist, well-draining, slightly acidic
- Hardiness
- Hardy to -15 °F
- Flowers
- June to September
- Growth
- Compact, rounded shrub
- Toxicity
- Toxic to dogs, cats, and horses
- Native to
- Japan and Korea
How to recognise it
- Flattened lacecap flower heads
- Outer ring of showy pale florets
- Center filled with tiny fertile florets
- Finely toothed, pointed green leaves
Caring for Mountain Hydrangea
Watering
Every 4 days- How often
- Deeply twice a week
- How much
- About 1 to 2 gallons around the base
- When
- Morning
- Tips
- Soak the root zone directly. Wet leaves from overhead sprinklers invite fungal spots.
Feeding
- How often
- Once in early spring and once in early summer
- What to use
- Slow-release balanced shrub feed
- When
- Spring
- How
- Scatter granules around the drip line and water in well.
Pruning
- When
- Late winter or right after summer flowering
- How
- Remove dead wood and cut spent flower heads back to a pair of healthy buds.
- Tips
- It blooms mostly on old wood. Heavy pruning in spring cuts off this year's blooms.
Jobs it will ask for
- Mulch the root zone Spread a 2 in layer of wood chips or compost around the base to keep roots cool and moist.
- Check for sun scorch Full sun can bake the thin leaves. If edges turn brown and crisp, provide midday shade.
Through the year
Spring
Feed with balanced fertilizer and keep soil consistently moist as fresh leaves emerge.
Summer
Water deeply during dry spells. Protect leaves from harsh afternoon heat.
Autumn
Taper off watering slightly as growth slows. Leave faded flower heads on for winter interest.
Winter
Apply a thick ring of leaf mulch over the base to protect crown buds from deep freezes.
What to watch for
- Wilting leaves in full sun
- Hydrangeas transpire water quickly. Move to a spot with afternoon shade or set up a shade cloth.
- Powdery mildew on leaves
- Avoid overhead watering. Water early in the morning so any splashed foliage dries quickly in the sun.
Reference photos
Compare what's in your garden with confirmed photos of Mountain Hydrangea.
Photos from iNaturalist contributors.
Written by Garden Rescue from photo identifications, in US units. Local advice from your extension service or garden centre beats a general guide.