Mountain Hydrangea 'Blue Billow'

Hydrangea serrata

Family: Hydrangeaceae (hy-drain-jee-AY-see-ee) (Info)
Genus: Hydrangea (hy-DRAIN-juh) (Info)
Species: serrata (sair-AY-tuh) (Info)
Cultivar: Blue Billow
» View all varieties of Hydrangeas


36-48 in. (90-120 cm)


4-6 ft. (1.2-1.8 m)


USDA Zone 5a: to -28.8 C (-20 F)

USDA Zone 5b: to -26.1 C (-15 F)

USDA Zone 6a: to -23.3 C (-10 F)

USDA Zone 6b: to -20.5 C (-5 F)

USDA Zone 7a: to -17.7 C (0 F)

USDA Zone 7b: to -14.9 C (5 F)

USDA Zone 8a: to -12.2 C (10 F)

Sun Exposure:

Sun to Partial Shade


Unknown - Tell us

Bloom Color:

Light Blue

Bloom Time:

Mid Summer

Late Summer/Early Fall



Other details:

Unknown - Tell us

Soil pH requirements:

5.6 to 6.0 (acidic)

6.1 to 6.5 (mildly acidic)

Patent Information:

Unknown - Tell us

Propagation Methods:

By dividing the rootball

From softwood cuttings

From semi-hardwood cuttings

Seed Collecting:

N/A: plant does not set seed, flowers are sterile, or plants will not come true from seed

Foliage Color:

Unknown - Tell us

Bloom Characteristics:

This plant is attractive to bees, butterflies and/or birds

Water Requirements:

Average Water Needs; Water regularly; do not overwater

Requires consistently moist soil; do not let dry out between waterings

Where to Grow:

Unknown - Tell us


This plant is said to grow outdoors in the following regions:

Marietta, Georgia

Saint Joseph, Illinois

Baltimore, Maryland

Catonsville, Maryland

Olney, Maryland

Roslindale, Massachusetts

Spencer, Massachusetts

Horton, Michigan

Warren, Michigan

Colts Neck, New Jersey

Mount Laurel, New Jersey

Tonawanda, New York

Broken Arrow, Oklahoma

Camden, Tennessee

Atlanta, Texas

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Gardeners' Notes:


On May 14, 2019, appylady from Greenfield, TN wrote:

We live in zone 7 and Blue Billow it is always beautiful. From the previous comments, mostly the negative ones were from much colder zones. Perhaps that is the problem. There are many more cold hardy hydrangeas available. Might give those a try . Happy Gardening!


On Jun 14, 2014, RemyO from Tonawanda, NY (Zone 6b) wrote:

After a very long colder than normal winter here in zone 6, it is covered in flower buds.


On Jun 18, 2012, NewMerciesFarm from HADLYME, CT wrote:

This is a great plant to appreciate in the shade in the dog days of July. In the right light the blue is electric and visitors are always drawn to the plant.

While all the US vendors refer to the species as serrata, Van Gelderen's Encylopedia of Hydrangeas lists it as Hydrangea Macrophylla (lacecap group) v. Blue Billow. Can anyone illuminate this point?


On Sep 27, 2011, rkwright85 from Horton, MI (Zone 5b) wrote:

Has been a strong grower and flowers well for me. I live in southern MI (zone 5b) and have it planted on the east side of my house for some winter protection. May need frequent watering if exposed to very much sun or wind.


On Jun 7, 2009, gardeneve from Roslindale, MA wrote:

This hydrangea is my best bloomer--no problems at all with later winter freezing of buds. The blue is so intense and the flowers last a long time. However it has not gotten as big as I expected--three years in my garden and it's still only a couple of feet tall (about 4 feet wide).


On Mar 22, 2007, Kristi_L from Kalamazoo, MI wrote:

Does beautifully planted facing east with full sun until noon near the faucet so it gets plenty of moisture.


On Jan 20, 2003, lupinelover from Grove City, OH (Zone 6a) wrote:

The buds are hardier than most cultivars, making it more likely to bloom in marginal areas. A spreading growth habit. Flowers are deep blue with dark centers.