Spiro

Viburnum

Variety Description

Variety used for comparison: Viburnum carlesii

Summary: The plants of 'Spiro' have strong vigour and are larger than those of Viburnum carlesii, which have medium vigour. The leaf blade of 'Spiro' is shorter than that of Viburnum carlesii. Along the longitudinal axis, the leaf of 'Spiro' is recurved while it is straight for Viburnum carlesii. The peduncle of 'Spiro' has an absent or very weak intensity of anthocyanin colouration whereas that of Viburnum carlesii has a medium to strong intensity of anthocyanin colouration. When nearly open, the flower bud of 'Spiro' is brown red whereas the flower bud of Viburnum carlesii is dark pink red.

Description:

PLANT: shrub, upright to bushy growth habit, medium to dense branching, strong vigour, hardy to United States Department of Agriculture zone 4

STEM: grey brown, medium thickness, absent or very sparse pubescence, round in cross-section, rough texture of bark, absent or very weak glaucosity, medium number of lenticels, no thorns/spines

PETIOLE: weak intensity of anthocyanin colouration
LEAF: simple, opposite arrangement, ovate, acute and acuminate apex, obtuse base, serrate margin, no lobing, strong pubescence on upper and lower side, very weak glossiness, medium to dark green on upper side, light green on lower side, no variegation, weak to medium intensity of anthocyanin colouration on veins of lower side, medium rugosity, absent or very weak to weak waviness of margin, recurved along longitudinal axis, weak degree of curvature

PEDUNCLE: absent or very weak intensity of anthocyanin colouration
FLOWER BUD: medium size, brown red (RHS 181A), globose, club-shaped including tube, rounded apex, absent or very sparse pubescence
INFLORESCENCE: compound cyme
FLORET: salverform, strong fragrance
COROLLA: inner side is white (RHS NN155C) with light blue pink (RHS 62C) blush at margin, outer side is white (RHS NN155C) with blotches of blue pink to light blue pink (closest to RHS 63C-D)
COROLLA TUBE: outer side is blue pink to light blue pink (closest to RHS 63C-D)

FRUIT: drupe type, outer surface is black when ripe

Origin & Breeding History: 'Spiro' originated from an open pollination conducted in 1999 by the breeder, Timothy D. Wood, an employee of Spring Meadow Nursery, Inc. in Grand Haven, Michigan, USA. The cross involved an unnamed female parent and unnamed male parent. The new variety was selected in 2000 based on strong fragrance, flower bud colour, plant vigour and ease of production. The Viburnum variety 'Spiro' was first propagated by softwood cuttings in the spring of 2009 in Grand Haven, Michigan, USA.

Tests & Trials: The comparative trial for 'Spiro' was conducted in an outdoor irrigated container trial during the spring of 2014 at BioFlora Inc. in St. Thomas, Ontario. The trial included 8 shrubs of the candidate variety and 10 shrubs of the reference variety. All shrubs were grown from rooted cuttings and transplanted into 13 liter containers in July 2011. Plants were overwintered in a polyhouse for two winters. The trial was arranged in rows with 1 metre spacing between rows. Bud observations and measurements were taken from 10 plants or parts of plants of each variety on May 8, 2014. Flower observations and measurements were taken on May 12, 2014. All other observations and measurements were taken on May 16, 2014. All colour determinations were made using the 2007 Royal Horticultural Society (RHS) Colour Chart.

Comparison tables for 'Spiro' with reference variety Viburnum carlesii

Plant height (cm)

Plant width (cm)

Leaf length (cm)

Colour of flower bud (RHS)

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Viburnum: 'Spiro' (left) with reference variety Viburnum carlesii (right)

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Viburnum: 'Spiro' (left) with reference variety Viburnum carlesii (right)

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Viburnum: 'Spiro' (left) with reference variety Viburnum carlesii (right)