Denomination: 'Shamrock'
Botanical Name: Hydrangea macrophylla
Applicant/Holder: Spring Meadow Nursery, Inc.
12601 120th Avenue
Grand Haven, Michigan
United States of America
Breeder: Corinne Mallet, Varengeville sur Mer, France
Agent in Canada: BioFlora Inc.
38723 Fingal Line
R.R. #1
St. Thomas, Ontario
N5P 3S5
Tel: 519-631-6241
Application Date: 2003-10-02
Application Number: 03-3852
Grant of Rights Date: 2007-08-23
Certificate Number: 2890
Date rights surrendered: 2008-08-25

Variety Description

Variety used for comparison: 'Izu-No-Hana'

Summary: 'Shamrock' has a glossier leaf blade than 'Izu-No-Hana'. 'Shamrock' has a slightly lower number of sepals in the large calyx than 'Izu-No-Hana'. 'Shamrock' has darker sepal colour than 'Izu-No-Hana'. 'Shamrock' has a wider sepal width than 'Izu-No-Hana'.


PLANT: upright bushy, hardy to zone 5

LEAVES: dark green on upper side, no variegation, medium glossiness, elliptic to obovate, acute apex, obtuse to cuneate base, no lobing, medium serrate margin

INFLORESCENCE: flowers with small calyx conspicuous, flowers with large calyx arranged in one circle, flattened shape
LARGE CALYX: blue pink, 12 to 14 sepals, sepals strongly overlapping, margins entire, sepals elliptic to obovate
SMALL CALYX: blue pink with tones of light blue violet

Origin & Breeding History: 'Shamrock' originated from a cross made in 1998, in Varengeville sur Mer, France. The female parent was an unnamed Hydrangea macrophylla variety and the male parent was unknown. 'Shamrock' was selected based on its unique double florets, a unique colour transition from white to pink to red, good bud hardiness and attractive foliage. The new variety was first propagated by softwood cuttings in the spring of 2000, in Varengeville sur Mer, France.

Tests & Trials: The tests and trials for 'Shamrock' were conducted in an outdoor trial at BioFlora in St. Thomas, Ontario in the summer of 2006. The trials included 10 plants of each variety. All plants were grown from 5 inch liners, planted into 2 gallon containers in May 2004 and transplanted into 3 gallon containers on July 2, 2004. Observations and measurements were taken from 10 plants of each variety. All colour measurements were made using the 2001 Royal Horticultural Society (RHS) Colour chart.

Comparison tables for 'Shamrock' with reference variety 'Izu-No-Hana'

Colour of calyx (RHS)

  'Shamrock' 'Izu-No-Hana'
large calyx N66D with N66C at margin N66D with 68A at margin
small calyx N74C with tones of 75B 75C-D

Width of sepal in large calyx (cm)

  'Shamrock' 'Izu-No-Hana'
mean 1.22 0.92

Click on image for larger view
Hydrangea: 'Shamrock' (left) with reference variety 'Izu-No-Hana' (right)

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