Clematis Plants : Clematis Varieties
The categories used below are designed so as to give you an overview of the different types of, known as clematis plants, available, and the various ways in which they can be used to best effect in the garden.
Clematis plants have been grouped in many different ways in the past; at one time no fewer than ten categories were used by a single company. I have attempted to simplify the system so as to reflect those criteria that are most useful for gardening purposes, such as the flowering times, the manner of growth and the consequent requirements of each plant.
Among the early large-flowered hybrids, the twice-flowering forms have not been separated from their relatives that flower only once. This is because their pruning requirements are the same, as are the various ways in which they can be used.
The genus Clematis must surely be one of the most diverse among the flowering plants, ranging from the tiny C. hirsutissima var. scottii to romping great thugs such as C. rehderiana. Between these two extremes we find a whole host of exotic large-flowered hybrids, both double and single. This diversity is one aspect that makes clematis such rewarding plants, offering so many different possibilities for gardeners to develop and experiment with new ideas.
Evergreen Clematis Plants
These clematis plants are among the most popular of clematis varieties. Unfortunately they are also responsible for some of the biggest disappointments.
The evergreens can be divided into two distinct clematis groups according to the two original species, Clematis armandii and C. cirrhosa (still sometimes called C. calycina). The armandiis come from China, while the cirrhosas are from the Balearic Islands in the Western Mediterranean. Although both groups of clematis plants are generally hardy, they do require some specialist treatment to give of their best.
Clematis armandii and its various cultivars have broad, leathery dark-green leaves that :re particularly prone to damage from cold winds; the plant is left looking brown and tired. Because of this the armandiis are best planted in a sheltered position that also gets a fair amount of sun. This is essential so that the wood can ripen and the flower buds can develop for the next season’s floral display. Thehave a delicious scent of vanilla, which can waft across the garden on warm spring evenings. C. armandii can be raised from seed, but is very variable in the size of ewer and the amount of perfume it produces. You can be more confident of success if you search out a named cultivar such as C. a. ‘Snowdrift’.
The cirrhosas are a little more temperamental, not in their growth or hardiness (they are very vigorous and as hardy as any other clematis), but in their ability to flower. They are often suggested as an ideal early-flowering plant – and indeed, given the right position and a climate that suits them, they can produce their cup-shaped speckled bells as early as January. The snag is that they need plenty of winter sunshine to give of their best. So they should never be recommended for gardens in the more northerly counties – or at least not unless they enjoy an exceptional microclimate.
If properly looked after, both clematis varieties – the armandiis and cirrhosas – will grow and thrive in common with other clematis plants. But especially after July or August, you should avoid feeding them with anything other than potash. Too much nitrogen late in the year can encourage soft growth with no time left for ripening before the winter frosts cut it back.
This group of clematis contains species and varieties that are among the first to flower, ranging from the compact to the very vigorous in growth.
Clematis alpina is a European species distinguished by its profusion of bright-blue nodding, bell-like flowers that open in April, or as early as March in a sheltered position. Among the various cultivars that have been produced, one of the best is C. a. ‘Frances Rivis’. This has much longer sepals than the species, with a wonderful light-blue colouring.
Clematis macropetala is a very similar species from China. It was introduced early this century, and differs from C alpina in having double flowers. The predominant colour is again a rich blue. Among the various cultivars, C. macropetala ‘Markhams Pink’ is the best known pink flowing form.
Alpinas and macropetalas grow to only 7-8 ft (2-2.5 m) in height. They produce their main crop of flowers in early spring, with only a few sporadic blooms appearing in late summer. However, the display of seed heads after flowering provides a bonus, extending the period of interest into the late spring. The ferny light-green foliage is an added attraction.
Both the species and their hybrids and cultivars will grow happily in any position. They are totally hardy. If grown in a cold position and not overfed, they will tend to produce deeper-coloured flowers.
Clematis Plants – Montanas
The montana group of clematis, unlike the alpinas, are well known for their vigour, create a profusion of star-like flowers in the early spring. Depending on the variety, they will grow to heights of up to 50 ft (15 m), and are most suitable for growing up quite large trees.
One of the major benefits to be obtained from growing light-pink or white-flowered montanas is the scent they produce on a warm spring day. Unfortunately, the darker-pink varieties of montanas and the allied species do not possess this characteristic. But species like Clematis vedrariensis have attractive foliage, which prolongs the period of interest.
Like the alpinas, the montanas flower in April to May, and will grow happily in a variety of situations; they will even tolerate quite deep shade.
Early Large-Flowered Clematis Plants
This group of clematis plants produces some of the largest flowers to be seen in the garden. If you look after them properly, cultivars such as the well known C. ‘Nelly Moser’ will produce a vast array of plate-sized flowers in early summer.
However, like all prima donnas they have to be carefully nurtured to create the full effect. All too often you will see poor Nelly strung up against a furiously hot wall, turning a gentle shade of grey above the yellowing leaves. Lots of water and potash are what’s required for Nelly and her ilk to thrive. They will need about 7 gallons (over 30 litres) of water per week throughout the summer months, adding some tomato fertiliser every fortnight or so.
Several cultivars in this group are particularly rewarding in that they flower twice in the season. The profusion of flowers appears in May or June, lasting several weeks. A lull during the main growth period is followed by yet another flowering in August, which is less abundant but just as rewarding.
Many of these clematis varieties also produce fat seed heads after flowering. These are quite attractive, and can either be retained on the plant or used for indoor decoration. Leaving them on the plant will not have any adverse effect, and they can be snipped off later when they have served their purpose.
This group of clematis plants includes a variety or cultiyar to suit almost every position in the garden. However, because of the size of the flowers, it’s best to find somewhere sheltered from the worst affects of any summer storms. The flowers are large but delicate, and their big surface area means they can be easily shredded by summer storms unless some protection is provided. On they other hand, all these plants are hardy enough to withstand the rigours of most English winters without any ill effects.
Double and Semi-Double Clematis Varieties
These clematis varieties are among the most exotic of all climbing plants to be found in the garden. They range from the almost peony-like blooms of Cleniatis ‘Proteus’ to the delicate yet abundant C. viticella ‘Purpurea Plena Elegans’.
Often you may purchase a double variety from a nursery or garden centre, take it home and plant it, and almost immediately a flower bud will appear only to open as a single flower. This is perfectly normal, and nine times out of ten there is nothing amiss. The reason is that the double varieties of clematis plants (with the exception of Clematis viticella ‘Purpurea Plena Elegans’) produce their double flowers only in May and June on the previous year’s growth; they will flower again later in the summer, but this time they only produce single flowers. It follows that newly purchased plants will have not had the time to produce enough wood for double flowers to develop.
To give of their best, these clematis plants require the same cultural treatment as the early large-flowered varieties. But they are best planted in a sunny position, where the summer sun will ripen the current growth to provide next year’s crop of flowers.
Sometimes a double white variety such as Clematis ‘Duchess of Edinburgh’ will produce green outer sepals. This effect will become even more pronounced if the variety is planted in a shady position, where the entire flower can become green – a phenomenon much beloved of flower arrangers.
Many of these clematis varieties are compact in growth. These are especially suited to growing in containers, where their large, heavy blooms can be given protection from the worst of the weather.
The value of the single flowers should also not be underestimated. Clematis ‘Duchess of Sutherland’ is perhaps one of the finest late-flowering reds available, while C. ‘Royalty’s myriad of single flowers carry on almost until the first frost of autumn sends the plant into dormancy.
The one exception among the double varieties is Clematis viticella ‘Purpurea Plena Elegans’. This vigorous plant will grow as much as 15 ft (4.5 metres) in a single year, producing its small, perfectly formed double violet blooms into late summer. The flowers hang well away from the plant, making it an ideal subject for growing up a light-coloured conifer. For despite being double, C. a ‘Purpurea Plena Elegans’ can be treated just like any other viticella: you can cut it back quite hard in the autumn, allowing the host plant to take pride of place before the final prune in February.
Clematis Summer Hybrids
These particular clematis share a number of advantages. Firstly, they flower at a time of year when other plants are past their best. More importantly, they flower on the current year’s growth, which means they respond well to hard pruning each year.
There is only one drawback: by the time these clematis plants have begun to flower, many if not all of the lower leaves have either yellowed or died, leaving the lower part bare and ugly. This makes the summer hybrids admirable subjects for growing through other trees and shrubs, where this unfortunate habit can be disguised by the host plant and only the growing and flowering portion remains visible.
The flower size of this group is less impressive than that of the early large-flowered forms. However, if you carry on feeding them with a high-potash fertiliser, the depth of colour can be markedly increased. You can also delay the flowering period somewhat by pruning extra hard and extra late – say, around March – which can provide a much-needed display of late-summer or early-autumn colour.
Even though these clematis are not normally recommended for growing in containers, it is possible to create a successful combination of Clematis ‘Comtesse de Bouchaud’ and C. ‘Lady Northcliffe’. If you first grow ‘Comtesse de Bouchaud’ up a tall structure, then allow the more compact lady Northcliffe’ to twine around the base, this can work extremely well over several years. ‘Lady Northcliffe’ only needs a light prune, while ‘Comtesse de Bouchaud’ should be pruned hard. The clematis plants will stay in flower for months, and the combination of light-blue and pink blooms will prove most effective.