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Bigleaf Hydrangea, Lacecap 'Shamrock'

Hydrangea macrophylla

Family: Hydrangeaceae (hy-drain-jee-AY-see-ee) (Info)
Genus: Hydrangea (hy-DRAIN-juh) (Info)
Species: macrophylla (mak-roh-FIL-uh) (Info)
Cultivar: Shamrock
Additional cultivar information:(PP16223)
Hybridized by Mallet
Registered or introduced: 2004
» View all varieties of Hydrangeas


36-48 in. (90-120 cm)

4-6 ft. (1.2-1.8 m)


4-6 ft. (1.2-1.8 m)


USDA Zone 4a: to -34.4 C (-30 F)

USDA Zone 4b: to -31.6 C (-25 F)

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)

USDA Zone 8b: to -9.4 C (15 F)

USDA Zone 9a: to -6.6 C (20 F)

USDA Zone 9b: to -3.8 C (25 F)

Sun Exposure:

Sun to Partial Shade


Parts of plant are poisonous if ingested

Bloom Color:



Bloom Time:

Mid Summer



Other details:

Unknown - Tell us

Soil pH requirements:

6.1 to 6.5 (mildly acidic)

6.6 to 7.5 (neutral)

7.6 to 7.8 (mildly alkaline)

Patent Information:

Unknown - Tell us

Propagation Methods:

From softwood 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:

Flowers are good for cutting

Flowers are good for drying and preserving

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

Water Requirements:

Average Water Needs; Water regularly; do not overwater

Where to Grow:

Unknown - Tell us


This plant has been said to grow in the following regions:

Baltimore, Maryland

Ithaca, New York

Bath, Pennsylvania

Gardeners' Notes:


On Jul 5, 2015, eyespye from Toronto,
Canada wrote:

Everything I have read on this plant is that it blooms on OLD wood, not new. I have had this shrub for about 7 years now and it only ever flowered once when we had a very mild winter...I am going to turf this one, sadly since it is taking valuable real estate in my garden. The leaves are a nice leathery dark green, but it's not grown for the leaves :-(


On Aug 29, 2005, lmelling from Ithaca, NY (Zone 5b) wrote:

I ran across this new cultivar today at a local nursery and decided to give it a try. It is a "Color Choice" plant from Proven Winners. This lacecap is purported to bloom on both new and old wood so would be a good choice for northern gardeners. Mine was not blooming at purchase, however the tag claims, "masses of large doubled, lace-cap flowers bloom white and matures to a stunning reddish pink (alkaline) or violet-purple (acid soil). Splendid in the shade garden as a focal point or foundation planting."

One thing noticeable about this as compared to other macrophya are the leaves, which appear a little darker green than some, and are slightly longer and narrower than others. The tag says that the blooms are nice for use in fresh or dried arrangements. Blooms mid-summe... read more