by Dr John Howells

First published in Garden News, Jul. 29th 1998

According to this year's 'Plant Finder' there are no less than 750 clematis commercially available. How does the gardener begin to know what clematis suits what he wants to do in the garden? I find that all the clematis can be neatly divided into twelve distinct groups. The clematis in each group have characteristics in common. So if you know one clematis in each group you know all twelve groups. Thus growing just twelve clematis leads to you knowing all the groups.

Group 1 is the Evergreen Group, so called because unlike the other groups they do not shed their leaves in winter and are thus evergreen. Together they produce bloom, and much of it, for the first three months of the year. Some will profit from being grown under glass.

The clematis I have selected for you, to represent this group, is Clematis armandii 'Apple Blossom'. This is hardy in most parts of the country and starts flowering about March. It likes a site out of the wind on a sheltered wall. It makes a very wide and high plant - up to 15ft (4.5m). It produces clusters of creamy-white flowers tinged with pink, bell-shaped at first and then opening almost flat; these are heavily scented, a real bonus at this time of the year.

Group II is the Alpina Group, a group of clematis with single bells. They flower in early to late spring and are compact climbers up to about 6ft (1.8m). They are very hardy. Inside the bell are petals called staminodes, which can be of a different colour to the tepals and so add to the attractiveness of the bloom. The blooms are followed by pretty seed-heads.

I would suggest you try C. alpina 'Frances Rivis'. This has the largest flower of the group and the flower has the most elegant shape. The tepals are a rich blue with white staminodes inside.

Flowering almost at the same time as the alpinas come Group III, the Macropetalas. They are a group of clematis with double bells. Here the staminodes protrude thus giving the impression of a double rather than a single bell. They are compact in habit and grow up to about 8ft (2.4m), are very hardy and make rather a larger plant than the alpinas. The seed-heads of this group are amongst the best of all clematis.

To get to know this group I would suggest that you try C. macropetala 'Markham's Pink'. The plant is covered with lovely double bells of bright pink tepals and creamy-pink staminodes.

Covering the period from late spring to early summer comes Group IV, the Montana Group of giant clematis. The clematis here are very vigorous, cover a large area, and produce flowers in profusion. Some can climb to 30ft (9.9m) and beyond. Many are scented. They make a dramatic element in the garden.

I would suggest you try C. montana 'Mayleen' which is very vigorous and easy to grow. It is strongly scented and has a large bloom - pink with golden stamens.

Group V are the dwarfs in the clematis world - the Rockery Group. Interest in this group has developed in recent years. Some of these clematis may need to be grown in the greenhouse. They are exceptionally attractive.

Try 'Joe' or its Dutch version 'Early Sensation'. This covers an area of up to 3ft (1m) square. The plant is covered with pure white or creamy-white flowers.

Group VI is that of the Early Large Flowered clematis. These are the showstoppers in the nurseries. They flower from late spring to mid-summer. This is the group unfortunately susceptible to stem-rot (clematis wilt).

Try 'Lasurstern' from Germany. It's vigorous, trouble-free and gives an abundance of bloom. The flower is handsome with rich deep mauve-blue tepals and white stamens. You will get a second crop in late summer. It grows up to about 12ft (3.6m). It flowers early in this group period. It is less susceptible to wilt than most in this group.

Group VII, the Late Large Flowered Group, also have large flowers and flower from mid-summer to early autumn. They are less susceptible to stem-rot (clematis wilt) than the previous group although it can still occur.

Try the outstanding clematis, 'Victoria', strong, very reliable and floriferous with rosy-purple tepals and buff stamens.

Group VIII is the Herbaceous Group and all these plants are suitable for your herbaceous border. Their flowering coincides with the previous group.

To show off this group I would recommend 'Durandii'. This has one of the finest blooms in all clematis with indigo-blue flowers of an interesting bell-shape and yellow stamens. It can clamber up to 6ft (1.8m). It makes an excellent cut flower.

Group X, the Texensis Group, is a group of climbing tulips. They make a bush up to 8ft (2.5m) and clamber happily over other plants. All are attractive but I will recommend 'Princess Diana'. This lovely plant has glowing pink tepals and creamy-yellow stamens.

Now we come to Group XI, the Orientalis Group, the group of yellow clematis. The nodding yellow flowers are an attractive lantern shape or bell-shape or an open bell. The group has fine foliage and has the bonus of spectacular seed-heads. They are all easy to grow.

To represent this group I recommend 'Bill MacKenzie'. It has a long flowering period, is a large plant and often has flowers and seed-heads together.

Group XII is the Late Mixed Group. Here we have a group of clematis that flower in late summer on to late autumn and thus extending the flowering period of clematis. Most of them make large plants with a big display of bloom. As the sun is limited at the time of the year when they grow they benefit from being in a sunny place.

I recommend C. potaninninii var. pottaninninii which used to be called Clematis fargesii. This makes a large plant up to 25ft (7.6m). The flowers are white. Give it plenty of room and it will be spectacular.

So with just twelve clematis you will have covered the whole range of clematis of different habits and flowering through the year. You will get to know which groups suit your garden and how to grow them.

Reproduced by kind permission of Garden News.

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