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Denomination: 'Radtko'
Botanical Name: Rosa
Applicant/Holder: The Conard-Pyle Company
8 Federal Road, Suit 6
West Grove, Pennsylvania
United States of America
Breeder: William J. Radler, Greenfield, United States of America
Agent in Canada: Variety Rights Management
475 County Road 18
R.R. #2
Oxford Station, Ontario
K0G 1T0
Tel: 613-258-9015
Application Date: 2004-07-09
Application Number: 04-4297
Grant of Rights Date: 2008-01-04
Certificate Number: 3104
Grant of Rights Termination Date: 2026-01-04

Variety Description

Variety used for comparison: 'Radrazz' (Knockout)

Summary: 'Radtko' has a smaller entire leaf than 'Radrazz'. The terminal leaflet of 'Radtko' is smaller than 'Radrazz'. 'Radtko' has an ovoid to globular shaped flower bud while it is pointed in 'Radrazz'. The flower bud at quarter opened is red while it is purple red in 'Radrazz'. 'Radtko' has stronger sepal extensions than 'Radrazz'. The sepal of 'Radtko' is slightly longer than 'Radrazz'. 'Radtko' has a slightly smaller flower diameter than 'Radrazz'. The shape of the upper part of the flower when fully opened when viewed from the side is flattened convex while it is flat for 'Radrazz'. 'Radtko' has a double type flower while it is semi-double in 'Radrazz'. The overall flower colour of 'Radtko' is dark purple red to dark pink red while it is purple red in 'Radrazz'. 'Radtko' has a smaller flower petal than 'Radrazz'. The flower petal margin of 'Radtko' has stronger reflexing and weaker undulation than 'Radrazz'. 'Radtko' has a white style while it is red pink in 'Radrazz'. The style of 'Radtko' has sparser hairiness than 'Radrazz'.


PLANT: upright to bushy to spreading growth habit, weak anthocyanin colouration on the young shoot, reddish brown hue of anthocyanin colouration on young shoot, linear to deep concave prickles/thorns on stem, sparse short and long prickles, very few to few prickles/thorns on pedicel, red brown prickles/thorns

ENTIRE LEAF: dark green to brown green, medium glossiness on upper side, 5-7 leaflets
TERMINAL LEAFLET: serrate margin, leathery texture, rounded base

FLOWERING SHOOT: flowers almost continuously for 6 to 10+ weeks in mid season, low number of hairs or prickles on pedicel
FLOWER BUD: ovoid to globular shape just before opening, red upon opening, red upper surface, dark pink red lower surface
SEPAL: strong extensions
FLOWER: round shape when fully opened when viewed from above, flattened convex shape when fully opened of upper part when viewed from the side, flat shape when fully opened of lower part when viewed from the side, centre infold, double type, dark purple red to dark pink red overall colour
FLOWER PETAL: outer middle zone purple red, outer margin blue pink, inner middle zone purple red, inner margin purple red, white petal spot on inner and outer side, petal spot on outer side is very small to small, petal spot on inner side small in size, medium reflexing of margin, weak undulation
REPRODUCTIVE ORGANS: white filament, long white style, no hairiness on upper half of style, stigma at the same level or just above the anthers, medium sized receptacle, receptacle pitcher shaped in longitudinal section, no prickles on receptacle
FRAGRANCE: weak to medium tea fragrance

DISEASE/PEST RESISTANCE: mildew resistant, black spot resistant

Origin & Breeding History: 'Radtko' was selected in June 1993 from a seedling population produced by a controlled cross of 'Carefree Beauty' as the female parent and 'Razzle Dazzle' as the male parent, in Greenfield, Wisconsin, USA in June 1992. Selection criteria included flower colour, long blooming season, black spot resistance, and shrub rose habit.

Tests & Trials: Trials were conducted during the summer and fall of 2006, in Oxford Station, Ontario. 10 plants of each variety were individually grown in 15cm pots in a polyhouse. Plants were spaced 35cm apart. Colours were determined using the 2001 Royal Horticultural Society (RHS) Colour Chart.

Comparison tables for 'Radtko' with reference variety 'Radrazz'

Entire leaf length (mm)

  'Radtko' 'Radrazz'
mean 83.83 104.00
std. deviation 5.34 6.32

Entire leaf width (mm)

  'Radtko' 'Radrazz'
mean 57.86 77.14
std. deviation 3.85 8.71

Terminal leaf length (mm)

  'Radtko' 'Radrazz'
mean 41.71 53.86
std. deviation 2.21 6.62

Terminal leaf width (mm)

  'Radtko' 'Radrazz'
mean 24.38 26.88
std. deviation 1.69 3.00

Sepal length (mm)

  'Radtko' 'Radrazz'
mean 39.00 28.17
std. deviation 5.97 4.07

Flower diameter (mm)

  'Radtko' 'Radrazz'
mean 65.43 69.25
std. deviation 3.60 4.33

Flower bud colour (RHS)

  'Radtko' 'Radrazz'
upon opening 45A/B N57A/B

Flower colour overall (RHS)

  'Radtko' 'Radrazz'
overall 53B/C 57A

Petal colour (RHS)

  'Radtko' 'Radrazz'
middle inner side N66A/53C 67B/N66C
margin inner side N66A/53C N66B
middle outer side N66C/N57C N66C
margin outer side N66C N66C

Click on image for larger view
Rose: 'Radtko' (left) with reference variety 'Radrazz' (right)

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