Clematis
To locate images associated with this article please visit our
image collection at Country, Farm and Garden Photo Library
Climbers are an essential garden element and are especially important in large country gardens where long fences and potentially monotonous wide-open spaces are common. Climbers soften the lines of otherwise harsh structures, such as fences and car-ports; they can provide shade when grown over arches, pergolas, gazebos; and they can be used as dividers or hedges when grown on frames.
Useful as climbers undeniably are, there are problems with them. In mild northern areas some, especially jasmine, tend to be far too vigorous and can rapidly take over a garden, However, for many gardeners the main problem is finding hardy evergreen climbers. There just aren’t that many climbers that are evergreen and flower well while also being reliably hardy. In most cases some form of frost protection is required. As that is usually impractical with a car-port or a pergola many otherwise desirable climbers are ruled out or consigned to more sheltered positions. Any introductions of new, hardy, flowering, evergreen climbers would be most welcome.
The only real alternative is to make better use of the hardy deciduous climbers and those few evergreens that are suitable, and that is where Clematis comes to the fore. This large genus (about 250 species) includes some of the most beautiful ornamental climbers, deciduous and evergreen, most of which are very hardy.
Most are vigorous climbers, some of which reach enormous sizes. Apart from the attractive flowers some clematis also have conspicuous seed heads. These are composed of rounded clusters of seeds attached to downy filaments. As the seed head matures it breaks up and the seeds are distributed on the breeze. Some species, especially Old Man’s Beard (C. vitalba), can become invasive but most do not self sow freely.
Most Clematis are forest or bush plants that grow with their roots in the shade and their tops in the sun above the foliage canopy of the trees. The flowers of our native New Zealand C. paniculata are a common sight here in spring, high in the trees. Indeed often you can only appreciate just how widespread this plant is by looking down on the foliage canopy from above.
While it’s difficult to replicate these conditions in a garden, Clematis will grow well provided the root zone is kept cool and moist. The simplest way to achieve this is to plant the vine on the shady side of a fence or other structure and allow the top to grow up to the sun. Mulching and shading with large stones will also keep the roots cool.
The genus can be roughly divided into four broad categories as follows. These divisions are primarily for the benefit of gardeners and have no strict scientific basis.
Small-flowered and less common species.
This group includes many of the smaller flowered New Zealand species and the mildly fragrant yellow flowered species, such as C. tangutica and C. rehderiana. They are generally collectors’ or novelty plants but include some very interesting and unusual species. Several attractive forms of C. texensis have been developed, including some very bright reds.
The best known of the these species is C. cirrhosa, which is sometimes sold as C. balearica. This species has deep green leaves composed of several leaflets and mature specimens are in flower almost continuously, even in frosty winter weather. The flowers are bell-shaped, creamy white with purple spotting, lightly scented and are followed by conspicuous fluffy seed heads.
‘Freckles’ is a cultivar of C. cirrhosa larger flowers with brighter spotting. It is certainly a more spectacular flower than that of the true species but some growers feel that its very brightness and size destroy the charm and grace that makes the species appealing.
C. nepalensis is a rare winter flowering species from the Himalayas. It too has cream bell-shaped flowers, as do most evergreen clematis, but its bright purple stamens and pollen are very distinctive. Although this species is not easy to find, it is easily grown and makes a superb garden specimen.
Another very unusual species is the leafless New Zealand native C. afoliata, which usually flowers in late winter and early spring. For most of the year this plant is a jumble of wiry green stems but for a brief period it produces weeping panicles of beautiful greenish-cream flowers that are sweetly scented. As with the brooms, the green stems are able to photosynthesise and perform the normal functions of leaves.
Simple large-flowered deciduous species and hybrids
This group is composed primarily of C. montana and its cultivars but also includes such species as C. alpina, C. florida, C. macropetala and their cultivars. They have small to medium-sized, usually single coloured, flowers in abundance. Except for the summer and autumn flowering C. viticella, they are usually spring blooming only.
Many forms of C. montana are available. The colour range is limited — mainly pink or white — and it can be hard to differentiate between the cultivars, but such minor niggles pale into insignificance when the plants are in full bloom because they are all beautiful. ‘Persian Fragrance’ is a relatively new introduction that is lightly scented.
Large-flowered evergreen species and hybrids
The best known of these species is C. armandii, which has long deep green leathery leaves and masses of fragrant white flowers in early spring. It is a rampant climber that can cover many metres.
The native C. paniculata should also be included here. Selected male forms provide the best flowers, although many seedlings, which inevitably include small flowered females, are still sold. The best selected male forms, such as the large flowered ‘Purity’, are becoming more widely available.
Fancy deciduous hybrids
The well-known Jackmanii and similar hybrids, such as those of C. viticella, make up this group. Although they have the most spectacular individual flowers they are often not as heavy blooming as the C. montana cultivars and they are the most prone to clematis wilt. However, healthy plants in full bloom are an unforgettable sight. There are many cultivars available with new introductions every year. The flowers may be single, petaloid centred or fully double. Some cultivars that have double flowers in spring may produce only singles later in the season but they will have double flowers again the following spring. No garden is really complete without at least one of these plants.
Most species and the common Clematis montana cultivars are not greatly troubled by pests and diseases, but clematis wilt is a major problem with the Jackmanii and similar fancy hybrids. This disorder causes entire stems to die back to ground level. Old established plants often have enough new growth to cope with the loss of one or two stems but clematis wilt often kills young plants. There seems to be no definite cure but there are a few reasonably successful preventative measures.
• Plant at the level of the first node or mound up the soil to the first node. This will encourage the formation of a stronger root system, which will lead to new shoots forming at the base. This will not stop clematis wilt but it will ensure a reserve of replacement shoots.
• Prior to planting soak the root ball in a systemic fungicide. After planting regularly drench the root zone with fungicide until the plant is established.
• Do not allow young plants to dry out during summer and feed regularly with mild liquid fertilisers. Strong steady growth is the best defence against any pests or diseases.
• Firmly tie young plants. Once established the plant will secure itself to whatever it is climbing over but until then strong winds are liable to twist the stems and split the bark, which may allow the entry of fungal spores.
Training
Clematis need to have their growth trained otherwise they will tend to sprawl over the ground or grow in all directions except where the gardener wants them to grow. Most are twining vines that will wrap themselves around wire mesh or trellis with great delight. A simple wire mesh-covered wooden frame, attached to the wall or fence is the easiest way to get them started.
Some clematis, especially the montana hybrids, can be used as ground covers. However, they have to be trained and cannot be left their own devices otherwise very straggly growth will result. Using galvanised wire and treated wooden pegs , lay a series of wires, about 10–15 cm above the ground, over the area you wish to cover. A pattern resembling the spokes of a wheel is the simplest to construct, as all of the wires radiate from the central peg or hub. Plant the clematis near the centre and tie its stems to the wire as the grow. The closer the wires are spaced, the quicker a dense cover will be established. I have to admit that my efforts with this method have not been a great success but I think it’s worth persevering with.
Some Clematis, such as C. rehderiana and C × durandii tend towards herbaceous growth and can be kept trimmed to bush like proportions. C × durandii is also suitable for growing as a ground cover as are many other species and hybrids. Some can be allowed to roam at will but others will need tying to pegged down wires like the montanas.
Pruning
Pruning is something that often confuses novice clematis growers. It is really quite straightforward and entirely determined by the flowering season.
• Those species and cultivars that flower in spring bloom on the old wood. They may be cut back hard immediately after flowering. This will ensure good summer growth and plenty of flowering wood for the following spring.
• Those that flower in spring and then again in summer or early autumn bloom on the old wood in spring and the new growth later on. Give these types a light corrective trim immediately after each flowering burst. They may be cut back hard if necessary to control the growth but doing so will reduce the quantity of bloom.
• Those that flower in summer bloom entirely on new growth. They may be cut back hard any time from late autumn to early spring.
Propagation
The species may be raised from seed, which often germinates better with a period of stratification. Hybrids and selected forms are usually grown from semi-ripe cuttings, which strike easily but are very prone to damping off and clematis wilt. Good hygiene and regular fungicide use are essential to avoid problems with wild diseases and damping-off.
******
With a good selection of plants you can have clematis in flower almost year-round. Their weight of flower, vigorous growth and easy care make them a first choice for any garden. What’s more they can be used as cut flowers, and the foliage can be used in floral decorations.
Copyright Geoff Bryant
|
