How to grow Clematis

 Clematis are one of the most popular garden plants because of their colourful and attractive flowers. Clematis are 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 which include the popular, late spring flowering Clematis montana, illustrated above right.  To keep clematis flowering well each year, pruning is required  which makes Clematis an "amber wheel barrow plant" 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

 Clematis are one of the few plants which are correctly planted below the soil level, so deeper than usual- see below the video How to plant Clematis.  Many Clematis are planting in spring and early summer but they can also be planted in autumn when the soil is still warm. Clematis need to be well watered when first planted which means if there is a dry spring extra watering will be needed. 

The main worry for most gardeners contemplating growing Clematis is how and when to prune them. 

The easiest  Clematis to grow because they need little or no pruning  are Clematis montana, C. alpina and C. macropetala. 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 Groups Explained

For the purpose of pruning all Clematis are classified into three groups:  

Group 1 the early flowering species which include the Montana (image  above right) and C. alpina, C. macropetala; shown in the  first image below left all require no pruning. Clematis Montana are one of the most popular Clematis mainly because of all of the group of Clematis they are easier to grow and very rewarding. C. montana are robust and quick growing flowering reliably each year. 

Group 2 early to mid season flowering (below centre image) Video How to prune Group 2 Clematis which require moderate pruning to a framework.

Group 3 are the late flowering cultivars, and small flowering cultivars Video How to prune Group 3 Clematis : 3rd image below right and this group all require a hard prune.

It can be tricky deciding which group a Clematis belongs to and so work out how to prune a Clematis. To help identify the Clematis in your garden The Sunday Gardener has a video which explains Clematis 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 to the Clematis group either  1, 2 or 3 Clematis, which then tells you how and when to prune it. If at all possible it is best to keep the label. This is not always possible, labels get lost and when you move house you may acquire a garden which already has a Clematis planted in it. The best way then to decide how and when to prune it is to take a note of when the Clematis flowers.  In which month a Clematis flowers can help to decide which group it is, this method is not infallible but if there is no label it is the best alternative as a rough and ready rule. There is more information below to help you work out which group your Clematis belongs to and when to prune it.

Videos: How to plant Clematis, Pruning Groups explained, How to prune Group 2 and Group 3 Clematis

How to Prune Clematis

Clematis Frankie

This is Clematis, one of the Alpina 'Frankie' early flowering late Feb/March Pruning Group 1

Clematis Nelly Moser

This is a C Nelly Moser which flowers mid summer and is pruning Group 2

Clematis jackmanii

This is one of the later summer flowering Clematis ' Jackmanii' which is pruning group 3.

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."

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  cut of the flowers. This group do not require pruning; but can be pruned after flowering if they are outgrowing their space.  

The next group of Clematis, very popular because they have large showy blooms and flower from Midsummer such as 'Nelly Moser', (Image above center) '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', others can have small flowers such as C. 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 make a note when the Clematis 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. This is is a broad brush approach as the 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 identification is not always easy. Now you know which Clematis or pruning group it is - what to do next ?

Clematis in late winter

Clematis in late winter it looks dead but it's not.

Clematis in late winter axil buds

A close up shows the same Clematis with axil buds

prune just above the buds

The same Clematis, prune just above a pair of axil buds

How to Prune different types of Clematis

Group 1 These flower early 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 above 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. In the second image the Clematis in winter looks dead it definitely is not; second image locate the axil buds and third 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 too 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', which has 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 they tend to be vigorous and can quickly out grow its space. Most of Group 3 need a lot of room and will overwhelm even a good sized shrub, such as a large species Rhododendron within a couple of seasons. 

More information about Clematis

How to Plant Clematis

Most clematis are frost hardy and 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 onwards. 

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 making it easy for the roots to grow into. Add peat free compost, fertiliser and water. Ease the Clematis out 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 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. 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.

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