The range of plants we call “clematis” is very extensive and, for ease of identification and description, botanists have divided them into groups or “subgenus”. Two main groups dominate the early spring in the UK, armandii and atragene.
Armandii
Armandii come from the sub-tropical regions of China, Tibet, Myanmar, and North Vietnam. Their natural habitats are wooded and shrubby areas and stream sides on hills. They have evergreen ‘strappy’ leaves and are well suited to scrambling along a fence, wall, or pergola. They grow well in most parts of the UK but, because of their sub-tropical origins, need a sheltered location, otherwise their leaves and buds will be scorched by wind and cold. They flower in March and April and can, apparently, be successfully grown in an unheated or cold conservatory but require quite a lot of space, growing to a possible height and spread of 4 metres.
There are three main varieties commonly available in the UK: Apple Blossom, Snowdrift, and Hendersonii Rubra. Some are also sold named only as armandii. All are fragrant with a strong smell of hawthorn or vanilla, depending on your sense of smell.
Armandii prefer damp, but not wet conditions, and thrive in full sun on a West or South facing but sheltered location. They can be planted at the same depth as in their pot, with the crown at soil level. I have three armandii and the two photos are of Hendersonii Rubra which has adorned this fence for many years and has required no pruning.
Atragenes
The atragene group of clematis consists of 17 sub-groups, but only three of these are really grown commercially and are widely available in the UK These are alpina, macropetala and koreana. They flower in March and April, producing some of the daintiest and reliable clematis flowers, which are bell shaped and hang down in profusion, dancing in the breeze. Some varieties may produce a second, smaller, flush of flowers in June or July. Atragenes need no pruning.
Atragenes are northern hemisphere plants, being found in Scandinavia and Central Europe, Korea, Japan, and North America. They grow in alpine forests and mountain regions but not above the snow line and not in monsoon areas. They will therefore take all the cold a UK winter can throw at them but require their root crowns to be in well-drained soil otherwise they will rot. (The crown is the point where the roots and stems meet, and this will be just below soil level).
There are many different varieties of atragenes to choose from and they are readily available from garden centres and clematis nurseries by mail order.
In general, alpinas such as Frances Rivis (see photo on the right), Pamela Jackman, Willy, Blue Dancer, can be regarded as single flowers.
In general, alpinas such as Frances Rivis, Pamela Jackman, Willy, Blue Dancer, can be regarded as single flowers whereas macropetalas such as Markhams Pink, Wessleton, Constance (see picture) Maidwell Hall look like double flowers.
Koreanas have slightly thicker sepals (outer petals) and leaves, but produce similar flowers to the macropetalas. Some also flower slightly later. Well known varieties include;
Brunette, Amber, Blue Eclipse, Broughton Bride (see photo).
Many of the varieties on sale in the UK are crosses between these three groups. For example. Broughton Bride is a cross between a koreana and a macropetala and was introduced by Vince and Syvia Denny in 1998.
Atragenes don’t need to be planted any deeper than they are in their pots. When planting in the garden I suggest that you add some sharp sand, grit, or gravel to the soil to improve drainage. I put two large handfuls of blood, fish and bone into the planting hole and add a general fertilizer around the base of the plants in Spring.
Atragenes grow well in pots and, if you add grit to a good peat free compost, they will reward you with many years of flower. I also add a slow release fertilizer like Osmocote 14-month feed.
If your garden is very wet in the winter, growing atragenes in pots is a good idea, but you could also try growing one in a large bottomless pot. Part sink the pot into the ground to provide stability and fill it with a gritty compost mixture as described. The crown of the plant will remain drier and the roots will go through the bottom of the pot in search of water and nutrients. Worth a try.
Cragside and Wesselton
Amber
Post script
There is a third group of spring flowering clematis called the New Zealand Group which contains varieties such as ‘Avalanche’ and cartmanii ‘Joe’. These varieties tend to flood UK garden centres in March and April and sell for, what I regard as, ‘eye wateringly’ high prices. I no longer grow them because I don’t regard them as being hardy enough for the garden, certainly not in Northern England where I live. They require over wintering in a green house, although I am told that they will survive on a sheltered garden wall. I am not convinced and therefore don’t recommend them as garden clematis.