Plant field guide
Hydrangea (Endless Summer)
The revolutionary bigleaf hydrangea that reblooms on both old and new wood — solving the cold-climate problem of late frosts killing next year's buds. Large mophead blooms in blue or pink depending on soil pH.
Growing requirements
- Scientific name
- Hydrangea macrophylla 'Bailmer'
- Sun
- partial shade
- Water
- high
- Height
- 36 in (91 cm) – 60 in (152 cm)
- Spread
- 36 in (91 cm) – 60 in (152 cm)
- Spacing
- 48 in (122 cm)
- Hardiness zones & minimum temperature
- USDA 4–9; average annual extreme minimum from -30°F (-34.4°C). Hardiness does not predict local frost dates.
- Difficulty
- moderate
Planting & seasonal timing
Northern Hemisphere planting months: not yet verified in our database.
Northern Hemisphere pruning months: August.
For the Southern Hemisphere, these seasonal windows shift approximately six months. Check your local frost forecast, soil temperature, and species requirements; calendar months are not a guarantee of planting safety.
Unlike old-fashioned bigleaf hydrangeas, Endless Summer reblooms on new wood — making it reliable even after harsh winters. Blue in acidic soil (pH below 6), pink in alkaline (pH above 7). Add aluminum sulfate for blue; lime for pink.
Pruning
Deadhead after first flush of bloom. Light cleanup pruning only — avoid heavy pruning that removes flowering wood.
Fertilizer
Balanced slow-release with iron for blue color
Early spring and midsummer
Mulch
4–6 inches organic mulch — critical in zone 4–5 to protect old wood from freezing.