How to grow Clematis
Clematis are one of the most popular garden plants because of their colourful and attractive flowers. Clematis are beautiful climbing plants with a wide range of flower shapes, sizes, colours and flowering times. The Pinterest page illustrates the many diverse shapes and sizes of Clematis, with new varieties being introduced every year.
Although very popular, Clematis are not the easiest climbing plant to grow and most need regular pruning, apart from Group 1 such as the popular late spring flowering Clematis montana, illustrated above right. To keep clematis flowering well each year, pruning is required and because of the pruning requirements, Clematis are labelled "amber wheel barrow" indicating medium attention and difficulty to grow. In addition, for newly planted young plants and at the beginning of the growing season, the spring growth is very attractive to slugs and Clematis need protection. Tips on how best to protect Clematis from slugs.
The correct planting of a Clematis is also important , and is detailed below and in the video on how to plant clematis. Clematis are one of the few plants which are correctly planted below the soil level, so deeper than usual.
The main worry for most gardeners contemplating growing Clematis is how and when to prune them. Some Clematis are easier to grow and maintain than others. The group which have little or no pruning requirements, such as Clematis montana, are easier to grow. Clematis montana is illustrated in the image below left and looks good planted with Spring flowering plants such as Alliums. One of the loveliest varieties, Clematis montana 'Elizabeth' has a beautiful vanilla scent. Of all the Clematis, when planting a Clematis montana you need a large space as it is is vigorous growing up to 12m (nearly 40ft) if left unchecked, and growing in ideal conditions. Clematis are fast growing and need to climb up a support, such as an obelisk, where they can provide height and be a feature in the border.
The different varieties of Clematis have a long flowering season, staring early in the year with the C. alpina right through to September the late flowering C. Tangutica, and over winter C. Cirrhosa. Clematis like well drained soil with sun or light shade. There are some Clematis varieties which are more shade tolerant listed below.
Clematis Pruning Types
For the purpose of pruning, all Clematis are classified into three groups:
Group 1 the early flowering species which include the Montana (image left) and C. alpina, C. macropetala; first image below left no pruning
Group 2 early to mid season flowering (center image) Video How to prune Group 2 Clematis; second image below center moderate pruning to a framework
Group 3 late large flowering cultivars, late flowering species and small flowering cultivars Video How to prune Group 3 Clematis : 3rd image below right Hard prune
It can be tricky deciding which group a Clematis belongs to and there is also a Video which explains Clematis Pruning Groups 1,2 and 3
The group to which group the Clematis belongs only matters to determine pruning requirements. When you buy a Clematis it will have a plant label which will state whether that particular variety of Clematis belongs to group 1, 2 or 3 Clematis, which then tells you how and when to prune it, so if at all possible, it is best to keep the label. This is not always possible, labels get lost and when you move into a house with an established garden it may already have Clematis planted in it with no information. The best way then to decide how and when to prune it is to take a note of when it flowers and there is more information below to help you work out which group your Clematis belongs to and when to prune it. When a Clematis flowers can help to decide which group it is, this method is not infallible but if there is no label or other information it is the best alternative.
This is Clematis, one of the Alpina 'Frankie' early flowering late Feb/March Pruning Group 1
Clematis 'Nelly Moser' a very popular traditional summer flowering Clematis Pruning Group 2
Clematis jackmanii a late flowering Clematis which for pruning purposes is Group 3
How to Plant Clematis
Most clematis are frost hardy and so can be planted at any time of the year. Like all plants it is not a good idea to plant when the weather is poor, or frosty. To give Clematis a good start it is best to plant during Spring, Summer or Autumn selecting a time without immediate frosts, generally a clement spell and rain after planting is good, providing it is not a mini monsoon. This tends to mean planting Clematis from April on wards.
The golden rule when planting a Clematis is to make sure that the root ball sits at least 5cms below the soil level - see image left. This is beneficial to the plant and helps to stop Clematis wilt. Dig a hole comfortably larger than the pot the Clematis is in. Make sure the soil at the bottom of the hole is not compacted so it is easy for the roots to grow into. Add some peat free compost, and water. Ease Clematis out of the pot and place in the hole.The easiest way to make sure you have got the depth correct, and to judge the depth, is to lay a bamboo cane across the hole so you can see the line of the soil depth and check the Clematis is a least 5cms below the soil level. Fill in, water some more and protect young growth from slugs. Clematis do well if their roots can be shaded whilst the rest of the plant prefers sun, not an easy combination. Like all new plants Clematis should be watered well after planting and keep an eye on the young plant, if there is a dry spell water regularly until the plant is established. A newly planted Clematis will benefit from cutting all shoots down to 15 -30cms the first year only. Watch the Sunday Gardener video How to plant Clematis
How to Prune Clematis
The only maintenance Clematis require is pruning, but that can be a problem. When you buy a Clematis it's label it will state to which of the pruning groups it belongs either 1, 2, or 3 and this is a very necessary guide.
If you are planting a new Clematis you can use the table below which sets out when to prune each group of Clematis. There is an old gardening saying, which might help if you are not sure what type of Clematis you have, "If it flowers before June, don't prune."
If you inherit a garden which has in it established Clematis, and you have no idea to which group the plant belongs, the only way to work it out which group is to see to when it flowers. Broadly, but not an absolutely fail safe method, when a Clematis flowers is a rough guide as to how and when to prune it. If you have no idea what it is, and no other way to identify it, this is the best you can do.
Flowering times for Clematis which flower early in the year, March, April, or early May are mostly likely to be of the groups known as Alpina, Macropetala and Montana which for pruning purposes are "Group 1" Their flowers are produced on growth made the previous year, which means the plant must not be pruned early in the year in the spring, or you will cut off the buds and branches on which the flowers are formed, and it would not flower that year.
The next group of Clematis, very popular because they have large showy blooms and flower from Midsummer such as 'Nelly Moser', (Image above centre) 'The President Niobe' and many other varieties are all known as "Group 2"
Finally, the late flowering Clematis are a bit confusing, some have large flowers such as 'Jackmanii', other scan be small viticella, so the flowers are different but distinguishable by the fact they all flower late in the season and are known as "Group 3"
If you can make a note of when the Clematis has flowered you can make a judgement on how to prune it : early spring flowering are usually group 1; summer flowering group 2 and later summer flowering group 3 although the only fail safe way is to fully identify the Clematis, and then to check to which pruning group to which it belongs. There are hundreds of types of clematis and new ones being bred all the time so its not easy; you can try this rule of thumb first. Now you know which Clematis or pruning group it is - what to do next ?
Pruning different types of Clematis
Group 1 These flower in very late winter, early spring and through to late Spring the latest to flower are the Montanas, and as a group require little or no pruning. Ideally these Clematis benefit from a light trim after flowering. Some of the Montanas are very vigorous and may need pruning to contain them in the space you have, in which case prune back to size you want, after flowering which will be late May.Avoid if you can any pruning after June as the Clematis is then producing wood (and flowers) for next year. Clematis in Group 1 can be left unpruned.
Group 2 Clematis Prune in late Feb/early March.These Clematis flower in early summer. In the image below the stems of the Clematis in Feb/March which may look dead, all brown and stringy, except you will spot little green shoots and you trim back to these shoots so the dead top growth is off, and where you can see the spurting new growth, this is kept on. In addition, to encourage new growth from the base prune back to say 30cms some of the more spindly growth. These are the more difficult Clematis to prune, see images below. In the second image the Clematis in winter looks dead it definitely is not; third image locate the axil buds and fourth image, prune back to axil buds and cut of top growth with no buds. By February and March Clematis are already growing and the top of the plant in particular will have buds and shoots on it. Do not worry that when pruning you are cutting off this new growth, plenty more will follow. Group 2 Clematis are pruned back more lightly to a framework of branches and buds; avoid pruning to hard as this may reduce flowering.
Group 3 The late flowering group of clematis pruning is easier here, cut off everything down to about 30 cms in Feb/early March. Group 3 Clematis need to be pruned hard every year. One of the most popular and readily available Clematis in this group is tangutica 'Bill MacKenzie', illustrated image below far left. Multiple lovely yellow flowers which provide fluffy seed head after flowering so a good garden plant. A reservation about this variety of Clematis is that it is a very vigorous variety and can quickly out grow its space and host. It needs a lot of room and will overwhelm even a good sized shrub, such as a large species Rhododendron within a couple of seasons. When planting ensure it has a very large space or host.
Clematis in late winter it looks dead but it's not.
A close up shows the same Clematis with axil buds
The same Clematis, prune just above a pair of axil buds