There are several thousand types of clematis.
All the deciduous types are fully hardy in the UK, the evergreen varieties are less so, with some being borderline.
Double and semi-double flowered types need a sunny, warm sheltered site.
It is often said they should be grown with their heads in the sun and their toes in the shade.
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Depending upon variety plants can grow to 12m (40ft) high / horizontally.
Groups;
Clematis are split into three groups according to their flowering times and the pruning requirements.
Group 1;
The species that flower from January to May on the previous season's growths. e.g. armandii, and montana.
If pruning is necessary then it should be carried out only when frost danger has passed or immediately after flowering.
Cut back long shoots to healthy buds and remove any dead wood.
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, 150-300mm (6"-12") above the ground just after flowering - don't do this again for at least three years.
Group 2;
The species that flower on short lateral shoots on the previous season's growths from late May to July.
In some seasons, in the autumn,another flush of flowers may appear, but generally not in the same profusion as the first.
There are a great number of hybrids in this group and so actual flowering times and durations can vary enormously.
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.
Prune in late winter after all fear of frost has passed, or early spring before any new growth has emerged.
Cut backlong shoots to healthy buds and remove any dead wood.
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, 150-300mm (6"-12") above the ground just after flowering - don't do this again for at least three years.
Group 3;
The species that flower in the leaf axils of the current season's stems from July onwards.
Well established plants should be pruned back hard or vigour and flowering performance will decline.
Another factor for pruning hard back is the flowering height.
If plants were allowed to grow on unhindered then the flowers would end up at the top of the plants well above the eyeline.
Prune in late winter or early spring when the buds are showing signs of growth and all fear of frost has passed.
Cut main stems back to a strong pair of buds 150-300mm (6"-12") above the ground.
If any stems have been damaged/killed cut them right out, back to ground level if necessary.
Each of these groups can be further split into;
a) The small-flowered species originating from the wild
b) The large-flowered hybrid varieties.
Clematis viticella have finely divided leaves and flower in summer / early autumn on the current year's growth
The bell-shaped flowers can be single (with four to six sepals), semi-double or double, and come in a wide range of colours, e.g. white, red, purple and blue.
They are hardy, surviving to temperatures of -37 °C (-35 ° F) and will grow in most soils providing they are not too dry or too wet.
They flower more profusely in bright sun, but will tolerate dappled / partial shade.
Once established, they need little care and are reasonably drought tolerant.
However with regular watering and high potash feeding they will fare much better.
Mulching over the root system in autumn will set them up nicely for the following year.
Viticella are easily raised from freshly sown seed, but will not necessarily turn out to be the same as the parent plant, to ensure this, take softwood cuttings in early summer,
Layering is another easy method of producing more stock.
Cultivation;
Week 3; Take hardwood cuttings of Clematis c. Montana by trimming the top of cutting just above a leaf joint, (node) and make lower cut about 100mm (4") below (inter-nodal).
Remove a 25mm (1”) long sliver of rind from the base of the cutting, dip cutting into rooting compound, then insert cuttings into gritty compost, place containers in a cold frame to root.
Week 10; Sow seeds sown in pots/pans or trays of seed compost and keep in warm location for two weeks.
Then place them in a cool location for 4-6 weeks e.g. cold frame at a temperature of around 2°- 4°C (35°-40°F)
Increase temperature slowly until seeds germinate.
Prick out the seedlings singly into 75mm (3") pots potting compost when large enough to handle and grow on in a cold frame until planting out time.
Week 13; Take layers and sever layers placed last year (if rooted) and replant where required.
Clematis that are being grown for ground cover can now be propagated by pegging down suitable shoots.
Prune Group 2 & 3 as necessary and check group 1 varieties for winter damage and trim.
Plant out new stock if ground and weather conditions allow.
Train new shoots to suit there location.
Week 18; (the following year) Pot up cuttings into 125mm (5") pots, and grow on in a coldframe until planting out time.
Week 23; As plants grow, train the new shoots in the right direction, by tying them into supports.
Week 27; Take stem cuttings 100-150mm (4"-6") long of half-ripened wood, trim to leave two buds at the base.
Insert in pots/trays containing a mixture of equal parts (by volume) peat and sand and place on a hot bed set to give bottom heat of 18°C (65°F).
When rooted cutting pot into 75mm (3") 3 in. pots of potting compost.
Overwinter in a frost-free coldframe or greenhouse.
Take more layers if required.
Feed mature plants with an organic fertilizer( but not when in flower) and mulch with compost to keep soil moist.
Check for mildew and treat as necessary.
Week 38; Prepare planting site by digging in plenty of well-rotted farmyard manure or compost to the soil.
Rake in bone meal at a rate of 100gms (4oz) per sq.metre.
Week 40; Plant out 1200mm (4ft) apart in any well drained humus rich soil, in a sunny or partially shaded position.
Alternatively; Plant out in early spring, when conditions allow.
Ensure that the planting location offers some shade at ground level.
Check pH prior to planting, Clematis require an alkaline soil, if necessary add garden lime to acid soils.
The planting hole should be dug alongside trellis, or a framework to support the plant as it grows.
Clematis supported on poles, pergolas and trees with a branchless trunk may initially need the main shoots tied to the support.
Those grown through shrubs usually twine without extra help.
If growing through a tree choose only healthy living trees for support, as dead ones may rot and collapse.
When growing plants against a building ensure that the roots are at least 300mm (12") away from the wall as this area can be prone to drying out.
In all cases plant out so that the base of the plant is level with the soil surface and fix it to a support stake for initial support.
Planting out;
There are some who would advocate that the planting depth should be to plant more deeply than it was in the container, with about 150mm (6") of soil over the root joint.
It is said this this method will reduce the possibility of clematis wilt, the choice is yours!
Which ever method you use add bone meal and plenty of well-rotted farmyard manure or compost to the soil.
Trim back the shoots to about 300mm (12") to encourage new ones.
Gently water in the plant and then continue to water only as necessary.
Keep the roots shaded with a thick mulch or with low growing plants.
Pale coloured, large flowered hybrids and those with two tone petals like a shady aspect.
Give evergreen and winter flowering species a warm position away from cold winds and draughts.
General rules;
- A good start can set them up for life.
- They benefit from feeding, especially in their formative years.
- Similarly from applications of well rotted manure applied in autumn or early spring.
- For a more instant fix to a weak plant, apply liquid seaweed fertiliser or one formulated for tomatoes throughout the growing season.
Aftercare;
Once established clematis need minimal care, in fact, a little restraint on the feeding front may temper their vigour.
Regular watering, especially in the first two years, is also required, but, once established, they are reasonably drought tolerant.
Plants with pale or two-tone coloured petals are best planted in a semi shaded position to prevent colour fading.
Evergreens and winter flowering species should be given a sheltered position avoiding cold easterly winds.
Always provide a support for the clematis at planting time, plastic mesh or trellis will do.
If you are growing up a wall or solid fence, fix the trellis / mesh to horizontal wooden battens spaced about 600mm(2ft) apart.
The young growths may need tying in from time to time.
Those grown through shrubs / trees usually twine without extra help.
Give high potash feeds during the growing season but before flowering, but don't feed when in flower.
Remember they like a lot of water during the growing season - up to a gallon a day in hot weather.
Wall trained plants; it is important to get bushy growth well down at the base during the formative years: cut all shoots back to within 225mm (9") of ground level the second spring after planting.
Thereafter, as soon as the buds start to swell in spring, remove all weak and dead wood and tie in young growths as replacement shoots.
These may be shortened in a restricted space by up to one-third.
Clematis climbing through trees require little attention apart from occasional thinning out in spring of old and dead growths.
If a tangled 'bird-nest' mass develops, this should be cut back well within the crown of the tree: remove all tangled stems to allow new growth to begin.
Deadheading with removal of a few inches of the stem encourages autumn flowering.
In restricted areas; it can be an advantage to train the first shoots horizontally, in the same way as an espalier is trained, about 300mm (12") above ground level.
From these permanent horizontal arms, the flowering stems will grow vertically.
Subsequent pruning, in spring, consists of removing all the previous season's stems back to a pair of plump buds near the bases of the vertical shoots.
