Butterfly Bush

Denomination: 'Pyrkeep'
Trade name: Purple Emperor
Botanical Name: Buddleja davidii
Applicant/Holder: Spring Meadow Nursery, Inc.
12601 120th Avenue
Grand Haven, Michigan
United States of America
Breeder: Elizabeth Keep, Kent, United Kingdom
Agent in Canada: BioFlora Inc.
38723 Fingal Line
R.R. #1
St. Thomas, Ontario
N5P 3S5
Tel: 519-631-6241
Application Date: 2003-08-12
Application Number: 03-3804
Grant of Rights Date: 2006-11-28
Certificate Number: 2638
Date rights surrendered: 2010-01-11

Variety Description

Variety used for comparison: 'Black Night'

Summary: 'Pyrkeep' is a butterfly bush variety that has shorter, more compact plants than the reference variety 'Black Night'. 'Pyrkeep' has stronger anthocyanin colouration on the stems than 'Black Night'. The flowers of 'Pyrkeep' are a lighter violet colour than the flowers of 'Black Night' which are very dark violet.


'Pyrkeep' is a variety of butterfly bush which has a bushy rounded growth habit. 'Pyrkeep' has a medium number to many branches and dense foliage. The stems are thin with strong anthocyanin colouration. The leaves are simple and elliptic in shape, with an acuminate apex and cuneate base. The leaf margin is finely serrate. 'Pyrkeep' has weakly glossy leaves which have very sparse pubescence on the upper side and dense, tomentose pubescence on the lower side. The main colour of the upper side of the leaf is medium green and the lower side is grey green.

'Pyrkeep' has an erect, panicle type inflorescence, with medium fragrance. The flower buds are oblong and blue violet in colour. The flowers are both terminal and axillary in position and salverform in shape. The flowers have 4 to 5 petals which are fused at the base. The petals have a rounded apex. The petal margins are irregularly dentate and medium to strong in undulation. The main colour of the upper side of the petals is violet, with violet blue at the margins. The corolla tube is orange red on the inner side and purple on the outer side.

Origin & Breeding History: 'Pyrkeep' originated from a controlled breeding program conducted during 1988 to 1993 between the female parent 'Adokeep' and an unnamed sibling of 'Adokeep' at the breeder's nursery in East Malling, United Kingdom. The new variety was selected based on its compact habit, new novel colour and larger bloom size. The new variety was first propagated by softwood cuttings in the summer of 1995, in East Malling, West Malling, United Kingdom.

Tests & Trials: Tests and trials for 'Pyrkeep' were conducted in an outdoor container trial in the summer of 2004-2005, in St. Thomas, Ontario. The trial included a total of 15 shrubs of each variety. All shrubs were grown from 4 inch liners, planted into 2 gallon containers in May 2004 and transplanted into 3 gallon containers July 2, 2004. Trials were arranged outdoors in rows with approximately 1 metre spacing between plants. Observations and measurements were taken from 10 plants of each variety on July 6, 2005. All colour measurements were made using the RHS Colour Chart 2001.

Comparison tables for 'Pyrkeep' with reference variety 'Black Night'

Plant height (cm)

  'Pyrkeep' 'Black Night'
mean 57.3 80.4
std. deviation 4.55 5.95

Plant width (cm)

  'Pyrkeep' 'Black Night'
mean 76.6 106.2
std. deviation 7.93 7.50

Length of inflorescence (cm)

  'Pyrkeep' 'Black Night'
mean 15.5 18.8
std. deviation 1.91 2.72

Colour of flower bud

  'Pyrkeep' 'Black Night'
RHS 86C 86A

Main colour of petal (RHS)

  'Pyrkeep' 'Black Night'
upper side N87D with 91A at margin 86A with 90A at margin

Click on image for larger view
Butterfly Bush: 'Pyrkeep' (left) with reference variety 'Black Night' (right)

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