All clematis require some form of support; that is in the very nature of climbing plants. Even the herbaceous species have insufficiently strong stems to be free standing. For many years, clematis have been thought of as climbers that needed to be grown up a wall. Clematis are ideal for growing up pergolas and archways.
Clematis are very useful for covering walls with interesting foliage, colorful flowers and often attractive seed heads. Extensive walled areas over 3.6-4.5 m (12-15 ft) in height and large gable ends of buildings are best served by C. montana types, due to their vigor. They will soon romp over such areas, covering them with foliage and, on an established plant, thousands of 5 cm (2 in) wide white or pink flowers. They are also excellent for disguising garden sheds.
Clematis do not cling onto walls as do ivy (Hedera spp.) or Virginia creeper (Parthenocissus henryana), for example. You will need to hammer in wall nails and then stretch wires 45 cm (18 in) apart between them, giving the clematis plenty of opportunity to wind their leaf tendrils around them. Clematis montana and its clan do not require annual pruning, so they are quite happy to be left alone smothering the wall or buildings until you feel they have outgrown their allotted space. Some of the best for this purpose are C. m. f. grandiflora (white) and C. m. 'Elizabeth' (scented pink flowers).
Alternative choices for walls and small buildings can be found in C. tangutica and C. tibetana. Again, wall nails and wire will be required. In theory, plants in this group need hard pruning but in such locations they can generally be trimmed with garden shears during the autumn or early spring to reduce some of their top growth, allowing fresh growth to develop and attach itself to the remaining old stems. Clematis such as C. tangutica 'Bill Mackenzie' are great value for money in such locations, producing their lovely yellow open cowbell-like flowers from mid-summer onwards to late autumn. Once the first flowers have finished, the gorgeous fluffy seed heads are produced. This clematis therefore produces its own plant association of attractive foliage, flowers and seed heads for approximately 4-5 months.
Walls of less than 3.6 m (12 ft) should have a range of other plants, either climbers or wall-trained shrubs, which clematis can be allowed to grow up and trail from in a natural way with, of course, a little direction from the gardener. Nearly all groups of clematis can be grown in association with other wall-grown plants, but it is worth taking time to select the clematis that will give the best effect. There are several things that should be taken into consideration, the first being whether the host and clematis should flower at the same time. If so, you must work out which color association you want- a matter of personal taste.
The large-flowered clematis cultivars including the early and double and semi-double types, the midsummer and later summer-flowering cultivars would all be suitable for growing with other wall-trained plants. The early and double and semi-double large-flowered cultivars would all benefit from protection from the wind or heavy rain given by shrubs such as ceanothus, pyracantha, winter-flowering jasmine, forsythia and Garrya elliptica. A number of evergreen shrubs are ideal, giving spring or summer flowers, some winter fruit, and year-round foliage cover.
Another aspect to bear in mind is that some clematis flowers fade in strong sunlight faster than others. If the plant association is for a south-facing wall, strong, deep colors must be chosen rather than the paler-colored clematis such as the pink/mauve striped C. 'Nelly Moser', or C. 'Hagley Hybrid' with its pale shell-pink flowers. Generally, the pinks and the paler striped clematis, such as C. 'Barbara Jackman', will also disappoint on a south-facing aspect. The pale blues usually retain their color, and deep blues and purples are also good; the deep reds, such as C. 'Niobe' and C. 'Ernest Markham', do not fade and in fact the latter is best suited to a sunny south-facing aspect, where its wood ripens better and it is more free-flowering. The pale mauve/pink striped and pink clematis are better grown on north-facing walls, where their flowers will not fade prematurely.
If you want the clematis to flower before the host, or perhaps afterwards, a range of choices becomes available. If the host plant does not require pruning, choose a light-pruning clematis. For example, C. alpina and C. macropetala types would be ideal, although the host would need to be 3-3.6 m (10-12 ft) high and of reasonable vigor or the rather dense foliage of the clematis would swamp it totally. These two groups of clematis have a great range of colored forms, through blue, mauve, pink and white. Although they are quite happy on a wall facing any direction, they are ideal for an exposed location facing north, northeast or northwest because of their very winter-hardy nature. They are also ideal growing by themselves on low walls or fences, where they will completely cover their allotted areas.
If clematis are required to flower after a spring- or early summer-flowering host, the later flowers such as C. 'Jackmanii' ,C. 'Victoria', C. 'Comtesse de Bouchaud' and C. 'Madame Edouard Andre' can be used. The C. viticella types are also suitable, producing plenty of small to medium-sized flowers in a range of colors from white to pink, mauve, red and purple. The clematis belonging to the C. 'Jackmanii' and C .viticella groups are most useful for growing through deciduous or evergreen host plants as their stems and foliage can be removed in late autumn so that the host looks at its best without being cluttered by untidy and soggy clematis leaves. The final pruning can be done in late winter. Both the C. 'Jackmanii' and C. viticella types are ideal for growing with wall-trained roses, giving additional color when the roses are flowering.
The best time for planning the association is when the host is flowering or in fruit, followed by autumn or very early spring planting for the clematis.
Clematis are ideal for growing up pergolas and archways. The less rampant species, such as C. alpina, C. macropetala, the large-flowered cultivars and the C. viticella types, would beautify the supports and lower parts of a pergola, but you would need the more vigorous C. montana types or C. tangutica or C. tibetana to clothe the top of a pergola or large archway and give shade beneath. The vigorous C. 'Huldine' would do well in such a situation and its flowers, which have semi-transparent tepals of pearly white with three mauve ribs on the underside, are best appreciated from below. Another choice would be C. viticella 'Polish Spirit', which has deep purple flowers.
A pergola should not be given over entirely to clematis as it would be very dull during the winter months. Combine the clematis with evergreen plants that will give interest in winter and allow the clematis to take over in summer. Late spring large-flowered cultivars can be planted to grow through the lower stems of ceanothus or pyracantha. Co viticella types such as the red-flowered c. v. 'Madame Julia Correvon' will give startling color during mid- and late summer. The green-tipped white flowers of C. v. 'Alba Luxurians' are nodding and blow around in the breeze just like butterflies, and the plant will grow to 3.6 m (12 ft). Another relatively new clematis, C. 'Petit Faucon, is a very free-flowering plant reaching only about 1 m (3 1/4 ft) in height. Its deep blue nodding flowers are produced for three months non-stop from early summer onwards, making it ideal for clothing the lower part of the support poles to a pergola. A near relative, C. 'Eriostemon', which grows to about 2 m (6 1/2 ft), would also be effective here. Both of these clematis need to be tied into their support or host as they are of a non-clinging nature.
Large trees such as pines can be clothed in flowers each spring if a C. montana in white or pink is planted to grow up into their branches. A well-established C. montana var. rubens growing up into a large old Corsican pine with large limbs, for instance, makes a perfect combination. When an established plant is in full flower in late spring it really can look like a pink waterfall cascading down the branches of such a majestic tree. C. montana types are also ideal for growing into established conifers such as thuja, giving interest each spring. However, the host tree needs to be of an open habit and at least 7.6-9 m (25-30 ft) in height. Smaller, more densely foliaged conifers would become overwhelmed and their foliage spoiled by the density of the clematis's growth.
Two of the less vigorous cultivars of C. montana are C. m. 'Tetrarose' and C. m. 'Freda'. The former has most attractive bronze-green leaves with serrated edges and its saucer-shaped deep mauve pink flowers are the largest of the C. montana group. It blends perfectly with golden-foliaged conifers. C. montana 'Freda' has the deepest colored mauve/pink flowers of all the group. It is ideal for growing into small conifers of only 4.5-6 m (15-20 ft) in height, and again will blend beautifully with the golden-foliaged forms.
Deciduous trees such as elm, beech and oak have such attractive skeletons in winter that they should not be used as a host for clematis. However, many of the fir trees, for example Douglas fir and Scottish pine, often have very bare trunks, especially when old, and this is not such a pleasing sight. The C. montana group can be used to disguise this, but other interesting clematis, such as C. tangutica and its forms and C. tibetana ssp, will give added interest, flower form, color and, of course, their delightful fluffy seed-heads which will stay on the plant right into the winter.
C. viticella group offer a good range of colors and look delightful flowering in moderate to small trees, such as cherry, Sorbus, lilac and hawthorn. The delicate pink/mauve-veined flowers of C. v. 'Minuet' look absolutely charming as they tumble down from a lilac tree. C. v. 'Alba Luxurians' growing into a sorbus with grey foliage makes a delightful picture in mid-late summer, while the pink-flowered C. v. 'Södertälje' raised by Magnus Johnson in Sweden is particularly stunning grown into young pine trees.
Holly trees (Ilex) also make great hosts for clematis. The almond-scented starry white flowers of C. flammula are a great sight in late summer growing through I. aquifolium. Its close cousin, C. x triternata 'Rubromarginata', also with tiny scented flowers which have reddish pink margins to the tepals, can be planted to grow through silver- or golden-variegated hollies.
Magnolias are marvelous small trees and their open framework of branches offer ideal sites for some of the mid-season large-flowered cultivars, such as C. 'Marie Boisselot', C. 'Henryi' (both white), C. 'General Sikorski' and C. 'Will Goodwin' (both blues).
Large evergreens such as rhododendrons can be used most successfully as hosts for clematis. Rhododendrons generally have a limited flowering period, mostly in the mid- and late spring, and need to be given added interest during the summer months and early autumn, so decorate them with the later flowering clematis to give an extra splash of summer color. There is a wide choice even from within this group and it is important to be selective. Old and straggly rhododendrons with bare lower limbs can be graced with any of the C. viticella group. Some of the glaucous-foliage rhododendrons will make ideal backgrounds for the white and pink/mauve C. viticella cultivars but darker-flowered cultivars, such as C. viticella 'Royal Velours' and C. viticella 'Polish Spirit', would be lost against the dark evergreen leaves of such a host.
Other small-flowered cultivars or somewhat distinct species, such as C. aethusifolia with its delicately cut foliage and charming tiny yellow bell-like flowers, look most attractive against the large leaves of rhododendrons. C. campaniflora, a close relative of C. viticella with small bluish-white flowers, and C. flammula would also be most attractive on such an evergreen, as would the compact C. tangutica 'Helios', which reaches only about 2 m (6 1/2 ft) and bears open lantern-shaped yellow flowers.
The dark foliage of English yew trees makes a splendid background for a range of white- or pale-flowered clematis. If the clematis are planted to grow into the outer branches, which on an old tree may be almost lying on the ground, a strong stake tied to the branches will give something for the clematis to anchor itself to, allowing it to get up into the tree. Only the hard-pruning type should be used so that the yew looks uncluttered during the winter months. Choose from the following clematis to achieve the best effect: C. aethusifolia (tiny yellow bell-shaped flowers), C. campaniflora (nodding white flowers), C. x fargesioides 'Summer Snow' (syn. C. f. 'Paul Farges') (clusters of white open flowers, suitable only on large, old trees), C. flammula (masses of tiny white star-shaped flowers), C. florida 'Plena' (unusual fully double creamy white flowers), C. 'Huldine' (8 cm/3 1/4 in wide saucer-shaped flowers), C. rehderiana (scented cowslip-shaped yellow flowers), C. serratifolia (nodding yellow lantern-shaped flowers), C. tangutica 'Bill Mackenzie' (yellow open bell-shaped flowers, only for large trees), C. terniflora (masses of white star-shaped flowers, for sunny areas only, as otherwise it is shy flowering) and C. vitalba (insignificant cream flowers but good for old unshapely trees where its much-prized fluffy seed heads will adorn the tree until mid-winter if left unpruned until late winter). If common ivy (Hedera helix) is covering the lower part of a large tree, its foliage can also be used as a host for any of the same clematis.
Roses and clematis are natural companions, each complementing the other. The best roses to associate with clematis are probably the old shrub roses, wall-trained climbers or ramblers and roses growing on posts, arch: ways, pergolas or freestanding poles.
C. viticella 'Polish Spirit' would be too vigorous for some wall-trained roses as it reaches at least 4.5 m (15 ft) in height and is rather dense in habit, but it would look outstanding grown over the climber Rosa 'Kiftsgate' or the rambler R. 'Bobbie James'. Of the clematis, the easiest for this purpose are those that repeat flower or produce their flowers in the later part of early summer. These can be pruned hard in spring. The early flowers are lost but the main crop is produced on the new growth, generally in midsummer. Some of these should be used as they add a wide range of colors to the C. 'Jackmanii' clan and also different-shaped flowers, thus giving added interest and form to the planting association. Some of this group are: C. Anna Louise (flowers: violet with red/purple bar), C. 'Elsa Späth' (flowers:mid blue), C. 'Gillian Blades' (flowers: white with wavy edges to the tepals), C. 'Kathleen Wheeler' (flowers: plumy purple with golden anthers), C. 'Lady Northcliffe' (flowers: Wedgwood blue), C. Liberation (flowers: pink with cerise bar), C. 'Masquerade' (flowers: mauvish blue), C. 'Mrs. Cholmondeley' (flowers: light lavender blue), C. 'Moonlight' (flowers: creamy yellow); C. 'Niobe' (flowers: deep red), C. 'Snow Queen' (flowers: white with red anthers), C. 'The President' (flowers: rich purple), C. Vino (flowers: petunia red), C. 'Warsaw Nike' (flowers: rich purple) and C. 'Will Goodwin' (flowers: pale blue).
Of the small-flowered species and their cultivars, particularly recommendable are C. aethusifolia, which has foliage that would bring charm to any rose, C. 'Arabella' (a non-clinging rosy purple), C. 'Durandii' (a non-clinging clematis with large flowers of deep indigo-blue), C. 'Eriostemon' (a non-clinging semi-nodding purple blue), C. flammula (scented starry white flowers) and C. Petit Faucon (non-clinging bronze foliage and intense deep blue semi-nodding flowers), which would be outstanding to cover the base of a rose up to 1 m (3 1/4 ft). Some of the C. texensis group would bring a variation of flower shape, for example the nodding-flowered cultivars C. texensis 'Etoile Rose' (deep pink flowers) and C. t. 'Pagoda' (pink mauve flowers), while C. x triternata 'Rubromarginata' with red-purple tips to its tepals and scented flowers would give charm and make a great combination with a large wall-trained rose.
Of the C. 'Jackmanii' group, which associate particularly well with the old shrub roses, good choices are: C. ' Ascotiensis' (bright blue flowers), C. 'Comtesse de Bouchaud' (bright mauve pink flowers), C. 'Gipsy Queen' (velvety violet purple flowers), C. 'Hagley Hybrid' (mauve flowers) for north walls, C. 'Jackmanii' (dark velvet purple flowers), C. 'Jackmanii Superba' (rich velvet-purple flowers), C. 'John Huxtable' (the only white flowers), C. 'Madame Edouard Andre' (dusky red flowers), C. 'Madame Grange' (dusky velvet purple flowers), C. 'Perle d' Azur' (outstanding sky blue flowers), C. 'Pink Fantasy' (pale pink flowers), C. 'Prince Charles' (mauve blue flowers), C.'Rhapsody' (sapphire blue flowers), C. 'Star of India' (purple blue with carmine bar flowers), C. 'Victoria' (rosy purple flowers) and C. 'Voluceau' (petunia red flowers).
The range of combinations is so vast that it is practicable only to give some general guidelines about this type of mixed planting with clematis and low-growing shrubs and perennial plants. There are two ways to approach this: either make a detailed planting scheme before any planting takes place or let the border establish itself and then note down some combination ideas during the period when the border is flowering or is of some other particular interest.
At the back of a mixed border, there is often a wall or a line of shrubs or conifers to give shelter and a backdrop for the plants in front of it. Formal hedges, such as yew hedges, should be left uncluttered by clematis, but if the hedge is informal and will require autumn trimming C. viticella types can be used as an added splashh of color and interest for the mid- to late summer months.
Sometimes small trees, such as the golden-foliaged Catalpa bignonioides 'Aurea', are used as a foil to the colorful perennials that flower throughout the summer and these call for a colorful clematis, C. v. 'Royal Velours' perhaps, which will blend with other reds or blues planted in the border. A clematis can be planted to enliven the border at all times of year. Evergreen clematis species and their cultivars, such as C. cirrhosa and C. c. 'Freckles', can be grown on a wall (generally a sheltered south or south-west-facing one), either alone or with other wall-trained climbers, to give foliage over the winter months and early flowers. C. alpina and C. macropetala types will provide early flowers, some summer flowers and interesting seed heads on a wall or fence, their density of growth giving protection to the perennials planted in front.
The early large-flowered cultivars, single, double and semi-double, could be grown with other deciduous or evergreen climbers or wall-trained shrubs to give early summer color, some repeat flowering to give late summer color also. These clematis are not suitable for fences or informal hedges but could be grown with structural evergreens such as free-standing Ceanothus or Viburnum tinus. However, they are placed best through wall-trained subjects which give protection to their large flowers.
Most large-flowered clematis can be used to grow at about 60 cm (2 ft) above ground level. C. 'Jackmanii', with its deep purple flowers, looks outstanding when grown through some of the red-flowered dahlias such as Dahlia 'Bishop of Llandaff' or D. 'Bednall Beauty'. The same clematis and C. 'Jackmanii Superba' make a pleasing contrast when grown with the variegated fuchsia, Fuchsia magellanica var. gracilis 'Variegata'. C. 'Madame Edouard Andre', with its dusky red flowers, also makes a good contrast when grown through other red or orange perennials, such as Potentilla 'Gibson's Scarlet'. The grey foliage of Phlomis fruticosa and its yellow flowers give the much- needed light background for the deep-purple clematis such as C. 'Madame Grange'. The bright blue flowers of C. 'Ascotiensis' mix well with pink-flowering plants, and would be outstanding with any cluster roses or through the young foliage of Rosa glauca.
C. integrifolia (blue flowers), C. i. 'Rosea' (pink flowers) and C. i. 'Alba' (white flowers) are splendid in mixed borders. They grow to about 60-75 cm (2-2 1/2 ft) and can be supported by small twigs or pea-sticks or just allowed to form informal mounds. Their flowers are nodding open bell shaped and C. integrifolia 'Alba' can be scented, though this is variable. The C. heracleifolia group, which are basically sub-shrubs, have enormous, usually pale green, leaves which give added dimension and form, and produce delightful pale blue hyacinth-shaped flowers which are generally scented, especially with C. heracleifolia var. davidiana, which also has scented leaves in the late autumn and grows to about 75 cm (2 1/2 ft).
