Denomination: 'PIIHM-I'
Trade name: Endless Summer Twist-n-Shout
Botanical Name: Hydrangea macrophylla
Applicant/Holder: Plant Introductions Inc.
2580 Antioch Church Road
Watkinsville, Georgia
United States of America
Breeder: Michael A. Dirr, Bogart, United States of America
Agent in Canada: BioFlora Inc.
38723 Fingal Line
R.R. #1
St. Thomas, Ontario
N5P 3S5
Tel: 519-631-6241
Application Date: 2007-12-07
Application Number: 08-6394
Grant of Rights Date: 2009-11-30
Certificate Number: 3688
Grant of Rights Termination Date: 2027-11-30

Variety Description

Variety used for comparison: 'Lynn' (Let's Dance Starlight)

Summary: 'PIIHM-I' has a taller plant height than 'Lynn'. 'PIIHM-I' has very strong anthocyanin colouration in the petiole and strong to very strong anthocyanin in the stem while 'Lynn' has absent to very weak anthocyanin in the petiole and stem. 'PIIHM-I' has a larger diameter large calyx than 'Lynn'. 'PIIHM-I' has more intense colouration of the small calyx than 'Lynn'. The small calyx of 'PIIHM-I' has purple petal colour while 'Lynn' has light blue pink petal colour. The anthers of 'PIIHM-I' are violet and the filaments are purple while the anthers of 'Lynn' are light blue pink and the filaments are white. 'PIIHM-I' has blue pink and purple bud colour while 'Lynn' has light blue pink bud colour.


PLANT: upright growth habit, remontant (reblooming) type, strong to very strong stem anthocyanin colouration

LEAF: medium green upper side, no variegation, absent to very weak glossiness, strong to very strong anthocyanin on midrib and margin edge, broadly elliptic, acuminate to acute apex, rounded base, no lobing, medium to coarse margin incisions, very strong anthocyanin in petiole

INFLORESCENCE: flowers with small calyx conspicuous, flowers with large calyx arranged in one circle, flattened lace-cap shape, peduncle with medium to strong anthocyanin
LARGE CALYX: strong intensity of colouration, purple to blue pink, maturing to light blue pink, four sepals, sepals medium to strongly overlapping, no margin incisions
SMALL CALYX: strong intensity of colouration, purple petal colour, violet anthers, purple filament, bud blue pink.

Origin & Breeding History: 'PIIHM-I' originated from a controlled cross pollination conducted in Athens, Georgia, USA in 2003. The female parent was the variety 'Penny Mac' and the male parent was the variety 'Lady in Red'. The new variety was selected from the progeny seedlings of the above stated cross based on continued evaluation for reblooming, increased resistance to mildew and improved leaf and flower characteristics. The new variety was first propagated by softwood cuttings in Athens, Georgia, USA in 2004.

Tests & Trials: Trials for 'PIIHM-I' were conducted in an outdoor trial at BioFlora in St. Thomas, Ontario in the summer of 2008. The trials included 10 plants of each variety, arranged in rows with one meter spacing between plants. All plants were grown from rooted cuttings which were transplanted into containers in the spring of 2008. Observations and measurements were taken from 10 plants of each variety on September 3, 2008. All colour determinations were made using the 2001 Royal Horticultural Society (RHS) Colour chart.

Comparison tables for 'PIIHM-I' with reference variety 'Lynn'

Plant height (cm)

  'PIIHM-I' 'Lynn'
mean 57.1 48.1
std. deviation 2.85 1.79

Large calyx diameter (cm)

  'PIIHM-I' 'Lynn'
mean 3.6 3.1
std. deviation 0.15 0.22

Large calyx colour (RHS)

  'PIIHM-I' 'Lynn'
new 67A-B 68A-B
mature 64C with 62B underlay N66C-D with 69B underlay

Small calyx colour (RHS)

  'PIIHM-I' 'Lynn'
petal 64A-B 55C-D
anther N77B 55C
filament 67A N155B (lighter than)
bud 64C with 74C tones 56A

Click on image for larger view
Hydrangea: 'PIIHM-I' (left) with reference variety 'Lynn' (right)

Click on image for larger view
Hydrangea: 'PIIHM-I' (left) with reference variety 'Lynn' (right)

Click on image for larger view
Hydrangea: 'PIIHM-I' (left) with reference variety 'Lynn' (right)

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