Clematis – a Talk by Marcus Dancer
Marcus owns a local nursery at Sandleheath near Fordingbridge specialising in growing and selling clematis for over 20 years. His talk for us at the March indoor meeting described the various groups of clematis, their growing conditions, their likes and dislikes and culminated in a demonstration of how best to prune the different classes. His talk was very informative and used large photographs passed around the audience rather than slides, which became a little chaotic at times. He tried to dispel some of the myths of growing clematis, why they can suddenly die, and that not all varieties should be planted deeply. Another myth is that the roots should be kept cool by shading the base with slates, tiles or stones. This is true only really for the large flowered hybrids and even so a better approach is to use a deep organic mulch as this is less prone to harbour slugs and snails than stones or slates. Clematis in general needs well drained soil in sun or partial shade.
Evergreen clematis includes the winter flowering and spring flowering varieties and all need particularly well-drained conditions and must never sit in waterlogged soil. These varieties can be rather tender and all should be planted in sheltered positions. They should never be planted deeply. For winter flowering a new interesting variety is C. urophylla 'Winter Beauty' with cream/white bell flowers. C. napaulensis looks dead during the summer but comes into leaf in the autumn and flowers in the winter, as does the cirrhosa group. Cirrhosa varieties (12-15ft) include 'Jingle Bells' white, 'Freckles' red/cream speckled, 'Landsdowne Gem' dark red.
Spring flowering varieties include the evergreen New Zealand hybrids 'Early Sensation' 8ft white and 'Fragrant Oberon' 6ft cream/green and scented. C. armandii has large leathery leaves but can be unreliable growing for some but not others, nicely scented with white flowers or white flushed with pink for the 'Apple Blossom' variety. Montana varieties are vigorous but never plant deeply. Varieties include 'Broughton Star' (double pink), 'Miss Christine' (white), 'Tetrarose' and 'Fragrant Spring' (pink scented), 'Freda' (pink but less vigorous with red leaves) and 'Warwickshire Rose' (dark pink with purple foliage).
Most clematis generally perform quite well in containers and for the tender evergreen varieties this has the advantage that they can be put in a cool greenhouse or conservatory during harsh winter periods. Use a well drained John Innes based compost with added grit and keep well watered and fed during the growing season. Repot in the dormant season every 4 to 5 years and reduce the roots by a third at this time.
The large flowered hybrids produce two crops of flowers, first on the old wood and the second crop on the new growth. With flowers up to 10 inches diameter, bold colours and with singles or doubles it is a large group. They should be planted deeply and need plenty of moisture and feed. This is the only group susceptible to clematis wilt and planting deep helps avoid this problem. Clematis wilt is a fungal disease which enters the plant through damage. Cut affected stems to ground level and treat new emerging shoots with a systemic rose fungicide. 10g baking powder to 1 litre water is effective against mildew or 1 part full cream milk to 10 parts water. Recommended varieties include 'Nelly Moser' (pink), 'Kiri Te Kanawa' (double blue), 'Josephine' (double mauve/pink), 'Fujimusume' (sky blue), 'Miss Bateman' (white with green flush), 'Westerplatte' (red), 'Denny’s Double' (double lavender), 'Vyvyan Pennell' and 'Piilu' (first crop double, second crop single).
The viticella group are similar to the large flowered hybrids but flower once during the whole summer, are very floriferous and hardy. Plant deeply in sun or shade and they reach 8 to 10ft in height. Varieties shown: 'Alba luxurians' (white with green flush), 'Jenny' (blue/mauve), 'Etoile Violette' (dark purple), 'Huldine' (white), 'Hagelby White' (pure white), 'Madame Julia Correvon' (wine/pink), 'Purpurea Plena Elegans' (double purple), 'Betty Corning' (bell shaped and scented) and 'Prince Charles' (pale blue).
The tangutica group are yellow, vigorous, late summer or autumn flowering and produce attractive seed heads. They have thin fibrous root systems and don’t need to be buried deeply but need sharp drainage. They prefer full sun or partial shade. Varieties shown: 'Golden Tiara', 'Lambton Park' (coconut scented), 'Bill MacKenzie', 'Glasnevin Dusk' (dark purple bells), C. triternata 'Rubromarginata' (hawthorn scented), C. rehderiana (cowslip scented bells), 'Anita' (white) and 'Treasure Trove'.
The texensis group is used for breeding giving rise to many popular hybrids such as 'Princess Diana' (pink trumpets), 'Gravetye Beauty' (red tubular flowers), 'Duchess of Albany' (pink trumpets), 'Etoile Rose' (bell shaped), 'Peveril Profusion' (pink), 'Kaiu' (small white/pink bells), 'Ruby Wedding' (maroon), 'Elf' (pink/white bells), 'Buckland Beauty' (small red/pink bells) and 'Sonnette' (bushy dwarf pink). The texensis group should be planted moderately deep and need full sun or partial shade.
The herbaceous group is a very large group and includes some highly scented varieties. 'Anna' is dwarf growing to 12 to 18 inches with yellow scented flowers during the summer. Integrifolia varieties have bell shaped flowers, thin wiry stems to about 3ft and scramble well over other plants or low shrubs, try 'Yvonne Hay' (blue scented), 'Hakuree' (white scented with lavender flush) or citrus scented 'Buckland Cascade' for hanging baskets. The Heracleifolia hybrids start to flower during late summer. They have large leaves, can be good for containers or shielding the base of taller leggy clematis plants, try 'Roundway Blue Bird' (dark blue scented 2ft self supporting), 'Sander' (white jasmine like scented 4ft), 'Cassandra' (dark blue 3ft), 'Eclipse' (dark blue 3ft), C. tubulosa 'Wyevale' (mauve blue scented 4ft). Taller varieties include 'Arabella', 'Miranda', 'Amelia', C. durandii and 'Mrs Robert Brydon'. C. x jouiniana 'Praecox' is good for ground cover.
The final group is the atragenes, including the alpinas with single flowers and macropetalas with double flowers. Very hardy, they flower in spring and don’t need to be buried deep. Sometimes they repeat flower in the autumn. 'Propertius' is a double pink slightly scented, 'Lagoon' double deep blue and 'Broughton Bride' is long flowering single white bells for the spring and double white later in the summer. For alpinas try 'Jacqueline du Pré' (mauve) and 'Blue Dancer' (blue).
Clematis fall into one of three groups when it comes to pruning which is necessary to prevent them becoming leggy and ensure they flower where you want them to flower. Feed also after pruning.
Group 1 includes the montanas, evergreens, alpinas and macropetalas. Prune after flowering to tidy.
Group 2 includes all the large flowered hybrids. Prune from January to March. Prune back to immediately above the furthest plump growth bud.
Group 3 includes everything else. Prune from January to March quite hard back to around 12 inches from the base if you want a bushy plant with maximum flowers. With thicker stems or neglected plants, cut back to around 3ft from the base or if you want it to scramble up a tree, leave it unpruned. With herbaceous clematis cut back to a growth bud around 4 to 6 inches from the base.
Marcus’s nursery is not open to the public, although plants can be collected by prior arrangement. He sells his plants through plant fairs, farmers markets and by mail order and has a comprehensive website devoted to clematis at www.clematisplants.co.uk.
First published in the Hampshire Group Newsletter Summer 2012
and subsequently in Cornucopia Issue 33.
© Copyright for this article: Peter Hart
This article was taken from a copy of Cornucopia that was published in 2014. You could be reading these articles as they are published to a national audience, by subscribing to Cornucopia.