Clematis
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It is unthinkable that the floriferous clematis would not be grown in so many European gardens as it is today. For sheer flower power, especially during mid and late summer, surely there is no sight that can surpass the clematis in full flower in modern gardens.
There are a variety of flower forms comprising of star-shaped flowers, nodding, bell shaped and flat flowers. Clothed in one or more cultivars pergolas, pillars and trees can be transformed into a floriferous spectacle. With careful selection, flowers can be displayed for a long period of the year. There are around 300 hundred species of clematis in the world and rather than attempt to cite them all here, but some are of little garden value, I have selected some of the best. For cultivation purposes, they are best divided into three groups for ease of cultivation, identification and pruning requirements, which is into Groups One, Two and Three.
When purchasing clematis plants from garden centre or nursery, ensure that you are aware of the correct pruning group, this should be displayed on the plant label, if not consult a member of the staff or look up in reference in books or on the internet. It is important to be aware and carry the correct pruning of your newly purchased plants in order to enjoy clematis to the best advantage.
Pruning Clematis
Group 1, early flowering species (Tidy after flowering)
These clematis flower on stems, which grew the previous year and produce their charming and delicate flowers before the middle of May. Flowers emanate from the leaf axil bud usually on the previous years growth. Clematis plants in this group are pruned only lightly in order to keep them tidy and within bounds, therefore only removal of any damaged or unwanted stems is necessary.
Group 2, early to mid season large flowered cultivars (Light prune in late winter)
Clematis in Group 2 also produce flowers from the previous season’s growth and should be pruned only lightly in late winter or early spring. These are early flowering large hybrid clematis and pruning consists of removing weak, old and crossing shoots, and shortening healthy stems by around a third of their length.
If left unpruned they will only produce small flowers amidst a tangle of stems, not the appropriate treatment for a queen!
Group 3 late flowered large cultivars (Hard prune in February)
Clematis Group 3 consists of all clematis, which produces flowers from mid-summer, around the middle of July, onwards. These clematis grow their stems and flowers during the same season after pruning on newly produced wood. During the autumn, the tangle of flowered stems may be thinned out, purely to tidy the plants, if desired, or left until February. Hard prune, that is cut down all stems to about 30 centimetres (12 inches), above the ground, without exception. Ensure that the pruning cut is fractionally above a pair of healthy buds. If not pruned, the plant will quickly become a mass of old diseased woody stems producing very few flowers.
Unless you prefer to keep the seed heads of some of the large flowered clematis hybrids on the plants for decorative purposes, you may consider removing the faded flowers in order to encourage more flowering.
Planting, Fertilising and summer care for your Clematis
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- Spring is the best time to plant clematis, the soil will have begun warming up and optimum growing conditions
prevail at this time of the year. Dig the hole at least twice as wide as the width of the rootball of the plant
and about 12 cms. (1.5 inches) deeper. On initial preparation, mix an equal proportion of well rotted down manure
or home produced compost with the garden soil plus a small handful of Fish, Blood and Bone in the planting hole.
Clematis, like roses, like a moisture retentive soil that does not dry out during the growing season hence the
requirement for manure or compost at planting time. The enhanced soil will provide a reservoir for moisture and
fertiliser to see the clematis through the season. ‘Cool, moist roots and a sunny top’ are the ideal conditions.
Ensure that the plant is planted those extra 12 cms. deeper that the top of the rootball. This procedure is
necessary in order to prevent Clematis Wilt, which is a disease best left in the text books! It ismanifest by the
top of previously healthy stems curling over and looking as though the plant is dry - cut out infected stems as
low as possible if this occurs.
- In order to achieve the optimum performance from your clematis, feed them once a week during April to late June, or when the flower buds are pea sized, with a high potash liquid fertiliser; a proprietary brand of tomato fertiliser is ideal. Fertilising beyond this period will accelerate the flowering period and cause it to peter out prematurely. On established clematis, water in to the base of the plant 4.5 litres (1 gallon) each time. However, if the soil is dry drench the base of the plants and allow to soak in before applying the liquid fertiliser. Each autumn apply a mulch of well rotted farmyard manure or home made compost to the base of the plant and cover with pea gravel.
- As described previously clematis like a cool and moist root system so ensure that watering is carried out during the summer, especially if there is a prolonged dry spell. The water must reach the deep root system and a useful method of ensuring this is to sink, a 300 cm, (1 foot) length of rigid plastic piping alongside the roots, and water and liquid fertiliser through this.
- Clematis will cling their petioles to anything nearby to give them support but errant stems may need assistance by tying in using soft twine or small plastic coated wire ties.
Clematis Sections (as designed by the author, there are variations in the public domain)
AGM= Award of Garden Merit as selected by the Royal Horticultural Society
Section one: The Evergreen section
Including:
afoliata, armadii, cirrhosa, paniculata, unciniata.
Best grown in the warmer gardens as they can succumb to winter weather; good for conservatory or heated glasshouse.
Section two: The Atragenes
Including:
alpina and macropelata
The are very hardy clematis and both species and cultivars flower on the previous seasons growth. Both have nodding flowers.
Section three: The Montana Types
Including:
chrysocoma, montana and x vedrariensis
Only use Montana if you have the space for it will ramble seemingly quite happily for miles! Ideal for covering old and unsightly building and trees.
Section Four: Early large flowered hybrids
Will thrive with other wall - grown shrubs or in containers. Large colour range and decorative seed heads.
| Species or cultivar | Description | Flowers | Prune group |
| Asao | Large, rose pink | 5,6,8 | 2 |
| Barbara Dibley | Petunia red; good cut flower | 5,6,8 | 2 |
| Barbara Jackman | Mauve, blue, magenta band | 5,6,8 | 2 |
| Beauty of Worcester | Deep blue, white anthers | 6,7 | 2 |
| Bees Jubilee | Mauve, pink bar | 5,6,8,9 | 2 |
| Carnaby | Dark pink, free flowering | 5,6,7,8 | 2 |
| Daniel Deronda | Blue, purple, strong grower | 5,6,7 | 2 |
| Dawn | Pink, best in light shade | 5,6,8 | 2 |
| Dr Ruppel | Deep, rose pink | 5,6,8,9 | 2 |
| Elsa Spath | Blue, red anthers | 5,6,7,8,9 | 2 |
| Fair Rosamund | White, rose bar | 5,6 | 2 |
| Guernsey Cream | Creamy yellow, large flowers | 5,6 | 2 |
| Horn of Plenty | Rosy purple, red anthers | 5,6,8 | 2 |
| John Warren | Deep pink, pointed sepals | 5,6,8,9 | 2 |
| Kathleen Wheeler | Mauve, gold anthers | 5,6,8,9 | 2 |
| Kiri Te Kanawa | Double blue, free flowering | 5,6,7,9 | 2 |
| Lawsoniana | Large rosy purple | 5,6,8 | 2 |
| Lasurstern | AGM Blue, cream anthers | 5,6,8 | 2 |
| Lord Nevill | Deep blue, red anthers | 5,6,8 | 2 |
| Miss Bateman | Compact with white flowers | 5,6,8,9 | 2 |
| Multiblue | Double blue, spiky sepals | 5,6,8,9 | 2 |
| Niobe | AGM Deep red, beautiful | 5,6,7,8,9 | 2 |
| Pink Champagne | Red/purple, free flowering | 5,6,8,9 | 2 |
| The President | Deep blue, popular plant | 5,6,7,8,9 | 2 |
| William Kennett | Lavender Blue | 5,6,9 | 2 |
Section Five: Late large flowering hybrids
| Species or cultivar | Description | Flowers | Prune group |
| Ascotiensis | Mid blue, green stamens. | 6,7,8 | 3 |
| Blue Angel | AGM Pale blue, crinkled edges | 6,7,8,9 | 3 |
| Comtesse de Bouchard | AGM Pink, free flowering | 7,8,9 | 3 |
| Ernest Markham | Magenta, old variety | 7,8,9 | 3 |
| Gipsy Queen | AGM Violet/purple | 7,8,9 | 3 |
| Hagley Hybrid | AGM Rose/mauve | 7,8,9 | 3 |
| Jackmanii | AGM Purple, old variety | 7,8,9 | 3 |
| John Huxtable | AGM White, beautiful | 7,8,9 | 3 |
| Lady Betty Balfour | Purple/blue, yellow anthers | 9,10 | 3 |
| Margaret Hunt | Dusky pink, vigorous | 7,8 | 3 |
| Madame Édouard André | AGM Red, a beauty | 7,8 | 3 |
| Perle d’ Azur | Sky blue, free flowering | 7,8,9 | 3 |
| Prince Charles | AGM Mauve blue, free flower | 7,8,9 | 3 |
| Rouge Cardinal | Crimson, free flowering | 7,8 9 | 3 |
| Ville de Lyon | Crimson, yellow anthers | 7,8,9 | 3 |
Section Six: The Viticella Types
This group of clematis, native to Europe, is wilt resistant, offers free flowering from late June until September and is very versatile.
| Species or cultivar | Description | Flowers | Prune group |
| Abundance | Wine red, free flowering | 7,8,9 | 3 |
| Alba Luxurians | White with green tips | 7,8,9 | 3 |
| Black Prince | Dark red, good in silver trees | 7,8,9 | 3 |
| Blue Belle | Violet, large flowers | 7,8,9 | 3 |
| Étoile Rose | Pink, nodding flowers | 7,8,9 | 3 |
| Ètolie Violette | AGM Purple free flowerer | 7,8,9 | 3 |
| Flore Pleno | Purple, double | 7,8,9 | 3 |
| Madame Julia Correvon | AGM Red, beautiful flowers | 7,8,9 | 3 |
| Margot Koster | Rose pink | 7,8,9 | 3 |
| Polish Spirit | AGM Purple, superb clematis | 7,8,9 | 3 |
| Purpurea Plena Elegans | AGM Violet, double old cultivar | 7,8,9 | 3 |
| Royal Velours | AGM Velvety red/purple | 7,8,9 | 3 |
| Venosa Violacea | AGM Purple/white, large flowers | 7,8,9 | 3 |
Section Seven: Late Flowering Species
A variable group of clematis species.
| Species or cultivar | Description | Flowers | Prune group |
| X durandii | AGM Indigo, good with gold foliage | 7,8,9 | 3 |
| flammula | White, pretty seedheads | 7,8,9 | 3 |
| florida ‘Alba Plena’ | White, double, sheltered spot | 7,8,9 | 3 |
| florida ‘Sieboldii’ | White, purple, quite beautiful | 7,8,9 | 3 |
| heracleifolia ‘Wyevale’ | Pale blue and scented | 7,8,9 | 3 |
| integrifolia | Deep blue, bell flowers | 7,8,9 | 3 |
| Orientalis ‘Bill McKenzie’ | Yellow, nodding flowers | 7,10,11 | 3 |
| tangutica | Yellow, nodding flowers | 7,8,9 | 3 |
| texensis ‘Aureolin’ | Yellow, free flowering | 7,8,9 | 3 |
| texensis ‘Etoile Rose’ | Deep pink, nodding flowers | 7,8,9 | 3 |
| texensis ‘Gravetye Beauty’ | Red, tulip shaped flowers | 7,8,9 | 3 |
| texensis ‘Pagoda’ | Pink/mauve, nodding flowers | 7,8,9 | 3 |
| texensis ‘Princess Diana’ | AGM Deep pink, a stunner | 7,8,9 | 3 |
| texensis ‘Sir Trevor Lawrence’ | Crimson tulip-like flowers | 7,8,9 | 3 |
| Vitalba | White, star-like flowers | 7,8,9 | 3 |
