Clematis
Flowering Vines

Buying Clematis

A difficulty in buying Clematis in much of North America is that despite the fact they are actually named cultivars, they are they are frequently only given the barest of descriptions, "red", "blue" etc. This means that you've got to try and work out which group they are in 1, 2 or 3.

This is not as difficult as it sounds however. Don't prune them at all until they've flowered! Large flowered varieties with 4-6" wide flowers will be group 2 or 3. If they flower before about June, they'll be group 2. Afterwards, group 3 (this is not an infallible system!). Group 1 are easier to spot. The flowers are smaller - though there are many more of them - and they flower early on in the year, with the first flush of spring flowers.

All deciduous types are hardy in all but harshest conditions and should be fine in zones 4 - 9, with these exceptions:
Clematis flammula - zones 6-9
Clematis florida - zones 6-9
Clematis montana - zones 6-9
Clematis texensis - zones 5-9

There are also some that are hardy from zones 3-9, but tend to be individual cultivars, rather than groups. In zone 3 if you want to try growing Clematis, out them in a sheltered position, ideally south facing against a wall and give them a good deep mulch in the fall and winter.

Clematis - Carnaby Clematis 'Carnaby' zones 4-8 full sun

Clematis - Jackmanii Clematis x jackmanii zones 4-8 full sun

Clematis - Niobe Clematis 'Niobe' zones 4-8 full sun

Clematis - Ernest Markham Clematis 'Ernest Markham' zones 4-8 full sun

Clematis - Henryi Clematis 'Henryi' zones 4-8 full sun

Clematis are an archetypal cottage garden plant. Along with roses around the door, any self-respecting English style garden could simply not get by without at least one and preferably several.

The group is very large and very varied, there are a great many true species and also a huge range of cultivated varieties. The only downside I can think of is that there are not very many available in the US currently and are not very widely available. Hopefully if these wonderful and generally easy to grow plants become more popular, then availability will increase.

The true species are often much easier to grow than the named varieties and suffer from less pest and disease trouble too.

Clematis climb by means of twining leaf stalks and so need something to hold onto. Like many climbers they do better if allowed to grow in three dimensions rather than two i.e. over a pergola, obelisk or similar rather than just up a trellis on a wall. having said that they can do well on a trellis, but expect them to grow outwards to some degree as well as up. A trellis / wall / fence behind a narrow border is good for them. If putting up trellis, keep it away from the brickwork a couple of inches with battens or spacers rather than try getting the plant to grow flush up against it - it won't and it won't like it either.

Don't ever plant anything within a foot of a wall, it's too dry there, plant away from the wall and direct the plant towards the wall if it is to grow up it.

They can also be allowed to climb over or through trees or shrubs and do well in pairs giving two complimentary or contrasting colors. Though make sure you don't mismatch the vigour or you might just get one of them taking over. The less vigorous late flowering types are good trained through large shrub or climbing roses.

Care of Clematis

All Clematis do best in reasonably light, slightly alkaline soil that is rich in nutrients. They don't do well in poor soils, heavy wet clays or strongly acidic soils. If your soil is heavy, then incorporate plenty (at least a bucketful) of organic matter, garden compost, well rotted manure or similar into the planting hole and mix well with the soil. Don't just dig a hole, fill it with organic material and then put your plant in the middle - well mixed is the key phrase here. If you've particularly heavy soil, mixing in some pea gravel will also help.

Clematis can be planted in containers, but not the strong-growing viticella or montana varieties (amongst others). Also bear in mind that a containerised climber should have the support contained within the pot too. If it's in a container and clinging to something else, things can get difficult when you come to move the container or if you decide it's time to re-pot. You also need to think about the positioning, a large Clematis clad trellis in a pot acts like a sail in the wind soon falling over. Position it in a sheltered place or anchor it in some way.

Clematis are plants of woodland clearings and hedges, in the main they like their roots to be in the cool, down amongst the shade and their heads up in the sun. There are Clematis for almost any situation, but different varieties have their own particular preferences of course.

Evergreen forms and some of the late flowering ones need (need - not would prefer) the shelter of a warm and sunny wall. Many of the early large flowered hybrids give their best colors if slightly shaded. In full bright sunlight, the colors can be bleached making the different varieties look very similar.

Planting: Clematis should be planted deeply, up to 6 inches below the soil mark on the plant in its pot. If your plant is small when putting it in the soil, it may be an idea to let it grow on a bit first in the pot.

Mulch Clematis well in autumn and again in spring with more organic matter. A top dressing of slow release fertiliser in spring is appreciated, gromore or blood, fish and bone - aka "The fertiliser of Beelzebub" (well known as this by me anyway) as it generally has Nitrogen: Potassium: Phosphorous N:P:K in the ratio 6:6:6 and it seems appropriate considering what it's made from too!

Feed Clematis through the growing season about every three weeks, but not when they're in full flower.

Pruning Clematis

Minimal early pruning and training required other than providing a support and tying shoots in where necessary - usually all that is needed is to guide them where you want them to go and allow them to twine of their own accord.

The pruning of Clematis varies according to flowering time. Plants are divided into three groups for this purpose.

Group 1: These flower early in the season on the previous years wood. If pruning is necessary (if you're happy with the size of plant and where it's growing, then by all means leave it until it needs it) then it should be carried out immediately after flowering.

Cut back too-long shoots to healthy buds and remove any dead wood only when frost danger has passed. Old congested plants can be thinned by removing about 1 in 3 woody shoots. If total renovation is needed they can be cut right back to the base, 6-12 inches above the ground just after flowering - don't do this again for at least three years though.

Group 2: The best known and most common Clematis belong to this group, large flowered hybrids that flower initially in spring and then again to a lesser extent later in the season. Prune in late winter or early spring before any new growth has emerged.

Prune as for group 1 above if required. This group generally need little in the way of pruning. If hard pruning is required, the spring flowers are usually lost, but the later flush in the first year will be much better, then the plant can get back to normal the year after.

Group 3: These flower late in the summer on growth made in that season. New growth is made every year from the base and so they can be cut back hard on a regular basis.

Well established plants should be pruned back hard or vigour and flowering performance will decline. Also, you may find that eventually the plant flowers up in the air somewhere and not at a sensible height if left to its own devices.

Prune in late winter or early spring when the buds are showing signs of growth. Cut main stems back to a strong pair of buds 6-12 inches above the ground. If any stems have been killed cut them right out, back to ground level if necessary.

Clematis Problems

Slugs and snails may be a problem on young tender shoots, as they are with loads of other plants. Mildew can be a problem in hot dry seasons later in the summer.

The biggest problem that can happen to your Clematis is something called "Clematis wilt". This is a disease that sometimes strikes (not that often, I've never experienced it in my own garden) with no warning or even any clear evidence of fungal infection.

The symptoms are obvious in that the plant dies back pretty much right down to ground level. Species varieties are less likely to be affected than the hybrid varieties. If this happens to your Clematis, then cut off all the top growth to just above ground level and dispose of it by burning or some other means than composting as you want to get any fungal spores out of the garden.

The plant should then produce new shoots from under the ground that are unaffected (this is why you planted it deep in the first place). If the same happens again, dig the plant up and throw it away (not on the compost heap).

If you really want to plant another Clematis in the same spot, you'll need to remove about 12" x 12" x 12" of soil from the spot and replace it with soil from elsewhere in the garden. Then re-plant with a species rather than a named hybrid. The easiest solution is to plant something else there and put your Clematis in a different spot.