Hydrangea Section Macrophyllae Cultivars K

Kanmara® Series

Apparently more a marketing concept by the Hydrangea Breeders Association than a specific series of cultivars, a ‘concept for high-end hydrangeas for patio and terrace […] perfectly suitable for exclusive clients’ (Hydrangea Breeders Association 2024). Plants are marketed by colour, Kanmara® in Pink, in White, in Deep Pink, in Champagne, etc, rather than under specified cultivar names (Kanmara 2024), although doubtless all are protected HBA cultivars. Sold in the pot plant market, they are marginal to our focus on open-garden hydrangeas.

'Kardinal'

(Teller Series, introduced 1987) Flowers tending towards red, although ranging to ‘the world’s most vibrant violet’ (Boebel 2011); the sterile flowers are sometimes in almost a double row; fertile flowers lilac/pink; sometimes with late flowers on side shoots. Vigorous, to about 1.5 m; glossy dark green foliage (Church 2007; Foster 2023; van Gelderen & van Gelderen 2004). One of the more popular and gardenworthy Tellers, blooming well even in upstate New York, (Boebel 2011). The name refers to the Cardinal, a North American passerine bird. The mophead ‘Cardinal’ is a different plant, a synonym of ‘Cardinal Red’.

Flower colour in Hydrangea 'Kardinal' extends to rich purple (Jardin Shamrock, Varengeville-sur-Mer, France; 19 August 2007). Image Koen Camelbeke (Arboretum Wespelaar).

Hydrangea 'Kardinal' at Jardin Shamrock, Varengeville-sur-Mer, France (19 August 2007). Image Koen Camelbeke (Arboretum Wespelaar).

Hydrangea 'Kardinal' tends towards red in flower. Image Maurice Foster.

Hydrangea 'Kardinal', one of the more popular and garden worthy of the Teller Series. Image Maurice Foster.

'Antique' tones in Hydrangea 'Kardinal' (Avenue Cottage, Ashprington, Devon, UK; 17 October 2023). Image Julian Sutton.

'King George'

Two different old mopheads with similar names, one British, one Belgian, have been confused here. Haworth-Booth (1984), who knew the plants before 1950, lists both as ‘King George’, and the earlier (British) one was certainly first published as simply ‘King George’ (Jones 1927). We have not checked the original publication of the Belgian plant, although the International Register gives it as ‘King George VII’ (sic). Modern use seems to have settled (apparently wrongly!) to the earlier, British cultivar usually being ‘King George V’. ‘King George II’ is occasionally listed. Caveat emptor!

1. Flowers mid-blue / rose pink, with large, serrate sepals, in a crowded head. Sturdy, to about 1.5 m in height (Foster 2023; Haworth-Booth 1984; van Gelderen & van Gelderen 2004). Introduced 1927 by the London nurseryman H.J. Jones, at that time an anomaly in Britain as a hydrangea breeder (Chrysanthemum, Phlox and Delphinium were among his other more fashionable interests). The original description, as ‘King George’ was as follows: ‘Bright rosy pink, large shapely truss, giant pip with fimbriated edge. Grand vigorous habit’ (Jones 1927). Plants were priced at 10s 6d, the equivalent of over £40 today.

2. Flowers deep blue / pink, sepals entire, late flowering, typically August–September in Europe. Stems pale green, not spotted; height to 1.25 m. Introduced 1938 by Emile Draps, Belgium; parentage given as ‘Rosebelle’ × ‘Merveille’ (Haworth-Booth 1984; van Gelderen & van Gelderen 2004; Hydrangea Derby 2024; Association Shamrock 2022)

Hydrangea 'King George' is an ambiguous name; this plant has entire sepal margins (form 2, above). Image Maurice Foster.

Hydrangea 'King George' (form 2, above). Image Maurice Foster.

'Kiyosumi-sawa'

Sterile flowers white, edged lilac-blue/pink. Potentially vigorous, 1.5 m in height or even more, although this is not everyone’s experience; a striking variety, popular in Europe. Found wild around 1950 on Mt Kiyosumi, Boso Peninsula, Honshu (Foster 2023; van Gelderen & van Gelderen 2004; Association Shamrock 2022). Maurice Foster (2023) notes that seedlings show a range of picotee flowers, and have garden value. It has been used by commercial breeders: for example, H. ‘Dolkis’ (DOLCE KISS), not described here, is a hybrid with an H. macrophylla (Google Patents 2024).

Late flowers and leaf pigmentation in Hydrangea serrata 'Kiyosumi-sawa', a wild-origin Japanese cultivar (private garden, Argyll & Bute, UK; 22 August 2023). Image Julian Sutton.

Hydrangea serrata 'Kiyosumi-sawa' has white, pink-edged sepals (Sir Harold Hillier Gardens, Hampshire, UK; 23 June 2024). Image Julian Sutton.

Hydrangea serrata 'Kiyosumi-sawa' is a potentially tall cultivar (Sir Harold Hillier Gardens, Hampshire, UK; 23 June 2024). Image Julian Sutton.

'Kizawa-no-hikari'

Sterile flowers double, with very narrowly elliptic sepals, pale lilac/red-pink though tending towards pink; fertile flowers yellow-green. Leaves narrow, very dark green on dark stems; spreading habit, to 0.75 m in height. ‘A brilliant combination of flower and foliage. Indispensable.’ (Foster 2023). Humid conditions might not be ideal. Japanese origin. (Foster 2023; Sous Un Arbre Perché 2024)

Hydrangea serrata 'Kizawa-no-hikari' has double sterile flowers with very narrow sepals. Image Maurice Foster.

Hydrangea serrata 'Kizawa-no-hikari', 'a brilliant combination of flower and foliage'. Image Maurice Foster.

'Klaveren'

Sterile flowers lilac/pink, with scalloped edges to the rounded sepals; fertile flowers pigmented; inflorescences large. Leaves dark green, sometimes colouring red or bronze in autumn; height about 1.25 m. Selected before 1990 by Breton hydrangea breeder Pierre Michel-Kerneur. (Foster 2023; van Gelderen & van Gelderen 2004; Association Shamrock 2022). ‘Striking’ and ‘first rate’ (Foster 2023).

Hydrangea 'Klaveren', a fine, striking cultivar. Image Maurice Foster.

Hydrangea 'Klaveren' in lilac. Image Maurice Foster.

Hydrangea 'Klaveren', an excellent lacecap which tends towards pink in flower, the sepals of the sterile flowers rounded, with scalloped edges (Darley Park, Derby, UK; 28 August 2023). Image Julian Sutton.

'Kluis Superba'

Flowers violet-blue / deep pink, crowded in large heads, the colour fading quickly. Very tall, to about 2.5 m. Parentage ‘Maréchal Foch’ × ‘La Marne’, introduced 1932 by Dutch nursery Kluis & Konig (Church 2007; van Gelderen & van Gelderen 2004). Double starred by Haworth-Booth (1984) but now largely superseded.

Hydrangea 'Kluis Superba', a tall cultivar (private garden, Ayrshire, UK; 24 August 2023). Image Julian Sutton.

Hydrangea 'Kluis Superba' at its bluest (private garden, Ayrshire, UK; 24 August 2023). Image Julian Sutton.

'Koby'

Flowers pale blue / pale pink, in very large heads about 20 cm across. Leaves rough, lime green; height to about 1.5 m; best in shade to prevent sun scorch to the flowers. Believed to be a sport on ‘Nikko Blue’ (but see the DNA sequence analysis of Wu & Alexander 2019). Selected before 2010 by Oregon nursery Hydrangeas Plus for its big inflorescences, the largest in their extensive collection; named for the nursery foreman’s baseball-mad son – his team, the LA Lakers, played in powder blue and white during the 1960s. (Hydrangeas Plus 2024; Association Shamrock 2022)

'Kocho-no-mai'

Sterile flowers double, with narrow sepals, pale lilac/pink, on long pedicles giving a loose, open inflorescence; fertile flowers few. Japanese origin. ‘Komochi Shichidanka’ is said to be the preferred name in Japan, but is almost never used in Western gardens. (Foster 2023; van Gelderen & van Gelderen 2004; Association Shamrock 2022)

Hydrangea serrata 'Kocho-no-mai' early in flowering: many of the unopened buds will be further sterile, double flowers (Windcliff Garden, WA, United States; 27 June 2023). Image John Grimshaw.

'Kolmgarip'

(Magical® / Everlasting® series) Flowers tending towards deep red-pink – ‘eyepopping’ (Boebel 2018)!. Glossy, olive green leaves; height to about 1.2 m. Introduced 2008 by Kolster BV, the Netherlands. Free-flowering and consistently eye-catching in the RHS trial (Foster 2023; Royal Horticultural Society 2018).

While Hydrangea 'Kolmgarip' (MAGICAL® GARNET) tends strongly towards pink (right), purplish shades are possible (left): nursery stock at Kolster BV, the Netherlands. Image Marco ten Hoope, Kolster BV.

Vivid pink Hydrangea 'Kolmgarip' (MAGICAL® GARNET) in commercial production at Kolster BV, the Netherlands. Image Marco ten Hoope, Kolster BV.

Hydrangea 'Kolmgarip' (MAGICAL® GARNET) (nursery stock at Kolster BV, the Netherlands). Image Marco ten Hoope, Kolster BV.

'Kompeito'

(Double Delights™ Series) Sterile flowers double, blue/purple/pink, with conspicuous white sepal margins; fertile flowers pigmented; claimed to be remontant. Height to about 1.2 m. Picky Michael Dirr (2021) considers it ‘among the best [doubles] I have grown/tested’ and has seen enough flowers on new wood in Georgia, USA to be ornamental. Experienced Tim Boebel (2018) rates it ‘hands down the most striking hydrangea I’ve seen’ but finds it flowers poorly in his Zone 6 New York State garden. Selected 2006 by Japanese nurseryman Toyokazu Ichie, parentage undisclosed; protected by US Plant Patent 20,998 and European Plant Breeders’ Rights; introduced in North America 2011 and sold in Europe (Google Patents 2024; Association Shamrock 2022).

Hydrangea 'Kompeito' STAR GAZER a double flowered lacecap with many admirers (Juniper Level Botanic Garden, NC, United States; 18 June 2023). Image Ross Bayton.

'Königin Wilhelmina'

Sepals serrate towards the tips, opening through greenish to violet / salmon pink, tending towards the latter, an unusual shade. Stems stout, height to 1.5 m. Introduced 1922 by Dutch breeder Baardse, named for the long-reigning Queen of The Netherlands. Once popular in Europe but now scarcely in the nursery trade. (Haworth-Booth 1984; Hydrangea Derby 2024; van Gelderen & van Gelderen 2004; Association Shamrock 2022)

'Koreana'

Flowers blue/lilac, ageing reddish, in flat inflorescences. Good red/purple leaf tints possible later in the flowering period. Height to 50 cm or so. In practice the name seems to apply to a clonal cultivar of uncertain origin; some claim it as originating in the same population as ‘Hallasan’ and ‘Spreading Beauty’, neither much seen, and not described here (van Gelderen & van Gelderen 2004; Association Shamrock 2022; pers. obs. 2023).

Hydrangea serrata 'Koreana': flowers of various ages (private garden, Argyll & Bute, UK; 22 August 2023). Image Julian Sutton.

Good leaf tints in Hydrangea serrata 'Koreana' later in the flowering season (private garden, Argyll & Bute, UK; 22 August 2023). Image Julian Sutton.

'Koria'

Sterile flowers with white sepals, sometimes faintly pigmented especially towards the base, ageing green, with striking fimbriated margins; fertile flowers bluish/pinkish. Neat habit; height to 1 m or so; highly rated in the RHS trial in southern England. Selected 2000 by Kolster / Horteeve, The Netherlands; protected by European Plant Breeders’ Rights (Royal Horticultural Society 2018; Hoko Breeding 2024; Association Shamrock 2022).

Hydrangea 'Koria' with heavily fimbriate sterile flowers. RHS Garden Wisley, UK; 23 July 2024. Image Jack Aldridge.

Hydrangea 'Koria', a striking lacecap (nursery stock at Kolster BV, the Netherlands). Image Marco ten Hoope, Kolster BV.

Hydrangea 'Koria' (nursery stock at Kolster BV, the Netherlands). Image Marco ten Hoope, Kolster BV.

'Kujusan'

Sterile and fertile flowers light blue/pink. Leaves heavily flecked white, best in shade to avoid scorching; height to about 0.6 m. Maurice Foster (2023) considers the aesthetic effect best when the flowers are blue, while admitting that the variegation can look like an infestation of red spider mite. Origin Japanese. (Foster 2023; Sous Un Arbre Perché 2024).

Hydrangea serrata 'Kujusan' is best grown in shade to avoid leaf scorching (White House Farm, Kent, UK; 12 July 2023). Image Julian Sutton.

Variegation on Hydrangea serrata 'Kujusan' can look disturbingly like a red spider mite infestation (White House Farm, Kent, UK; 12 July 2023). Image Julian Sutton.

Hydrangea serrata 'Kujusan' has light blue or light pink flowers (White House Farm, Kent, UK; 12 July 2023). Image Julian Sutton.

'Kurenai'

Sterile flowers white with 3 or 4 sepals, maturing through pink to red (often particularly intense, especially with good light levels), the centres usually paler; later flowering than many, typically July–August. Height to about 1 m; sometimes weak growing. Japanese origin. ‘Kurenai-nishiki’ is an irregularly yellow-variegated sport, very occasionally seen in Europe. (Foster 2023; van Gelderen & van Gelderen 2004)

Hydrangea serrata* 'Kurenai' reaching its best late colour at Etang de Launay, Varengeville-sur-Mer, France (10 August 2023). Image Jack Aldridge.

Hydrangea serrata 'Kurenai' flowers are typically pink at their peak (Castle Howard, N Yorkshire, UK; 7 July 2024). Image John Grimshaw.

Hydrangea serrata 'Kurenai' at its finest (Castle Howard, N Yorkshire, UK; 7 July 2024). Image John Grimshaw.

Sterile flowers of Hydrangea serrata 'Kurenai' can age to a lovely, intense red (private garden, Argyll & Bute, UK; 22 August 2023). Image Julian Sutton.

'Kurohime'

Sterile flowers purple/pink, fertile flowers pigmented. Stems and petioles a distinctive dark purple-black; leaves can take on purple tints in sun (Hydrangeas Plus 2024; Sous Un Arbre Perché 2024; van Gelderen & van Gelderen 2004). Found by Takeomi Yamamoto before 1960 in the Manyo Botanical Garden, Nara, Japan (Association Shamrock 2022), a garden devoted to plants mentioned in the 8th century Man’yōshū poetry collection. The name translates as ‘Black Princess’.