Growing clematis in Containers
By Howard Drury
Everyone knows that Clematis are excellent climbing plants for walls, fences, trees and shrubs but not many people grow them in containers. All too often the results are disappointing, but this can easily be avoided if a few simple rules are followed. For detailed advice on growing all types of Clematis please see Fact Sheet entitled Clematis
Varieties to choose
The correct choice of Clematis is vitally important as not all varieties are suited to container growing. The cultivars to choose are the large flowered May-June flowering types which will also produce a second flush of flowers in August. The cultivars listed below are specially recommended for growing in this way.
Arctic Queen Double white flowers
Asao Deep pink flowers
Daniel Deronda Deep purple flowers
Fireworks Blue flowers with petunia red bar
Mrs Truax Periwinkle blue flowers
Guernsey Cream Cream yellow flowers
Peveril Pearl Pale lavender flowers
Pink Champagne Cerise flowers
Silver Moon Silver mauve flowers
Sunset Red flowers with a purple edge
Vino Petunia red flowers
Types of container
Always choose a terracotta, stone or wooden container. These will help to keep the roots cool in summer and will afford some protection from frost in winter. Plastic containers are definitely not suitable. The container must be at least 45cm (18") deep and 30cm (12") wide to allow for root development. The pot should be raised from the ground on "pot feet" or bricks to keep drainage holes free. There are some recycled containers with good insutlation properties to keep roots cool in summer and warm in winter.
Good drainage is imperative. Make sure the container has plenty of drainage holes and then cover the base with a 50mm (2") layer of broken pottery and small pebbles. Use a John Innes No.3 compost and plant the Clematis with the root crown about 75mm (3") inches below the soil surface. This is one of the few plants that should be planted more deeply that the level at which it was originally grown. By doing this you will encourage it to shoot from the base - particularly important if the plant is cut back by frost or Clematis wilt. You will also be able to add a few bedding plants to the container when the Clematis is newly planted without disturbing its roots. These will help to keep the roots cool. Dark coloured flowers will fade in bright sunlight and the container should be positioned so that it is not in full sun all day long.
Clematis 'Crystal Fountain'
Clematis under Acer
Raymond Evison of the Guernsey clematis nursery has bred to outstanding series of clematis especially for growing in pots and containers. First launched at Chelsea around 2005 Raymond has been adding to both series and exploring more widely how these clematis can be best used.
The Boulevard series are also known as compact patio clematis and are of a bushy habit and usually to foot to 5 foot in height depending on cultivar. All clematis in this series have exceptionally long flowering periods from spring until late summer. They are usually hard pruned to 15 cm in spring when they will make vigourous regrowth before flowering.
They are generally very easy to care for and in recent years Raymond has begun to demonstrate how they may be used in many ways other than a simple clematis in a pot concept. He has demonstrated how they may be used as a single subject in window boxes, hanging baskets and other containers and most recently has shown how they may be mixed in window boxes and other containers with a whole range of other garden plants.
Rebecca is named after Raymond Evison's oldest daughter Rebecca and was launched at the 2008 RHS Chelsea flower show. It is happy planted in the garden or in a container and will grow either. It will reach 2 m in height and flower from early summer until autumn, in the spring it should have top growth reduced to 15 cm as the buds begin to swell.
The second series Raymond introduced are called the patio and garden collection as they typically grow 1.6 to 2 m plus in height making them ideal for use on archways covering fences trellis or pergolas. One of their particular attributes is that all plants in this series have a long repeat flowering period from early summer until early autumn.
One of the best in this series is Rebecca which was launched at the 2008 RHS Chelsea flower show and named after Raymond's oldest daughter Rebecca. It will reach up to 2 m in height and produces masses of deep red blooms from early summer until early autumn. The following spring all top growth can be reduced to 15 cm as the buds begin to swell.
There are many other clematis in these two series and more information can be found on the Raymond Evison's website and while his nursery is strictly wholesale the better garden centres will stock plants most times of the year.
The Clematis will need a support to climb. You can make your own from cane or trellis but there are several styles of plant support available which make quite attractive features in their own right, whilst you are waiting for your plant to reach the top. It will take about three years for the Clematis to cover a support. Tie in the stem, loosely, to encourage the plant to climb.
Feeding and watering
Clematis are greedy plants and need regular feeding and watering. Use a general purpose liquid fertilizer in the growing season but stop when the flower buds are about the size of a pea. Once the flowers have faded you can start to feed again to encourage a second show. Don't let the container dry out and in hot weather it will need at least half a gallon of water every day.
These Clematis produce flowers on the previous season's ripened stems and in February/March remove any dead stems and shorten back the remainder to around 24" and tie in new growth as it appears.
Pests and diseases
Aphids (Greenfly) common in early summer, clustering around the growing shoots causing the leaves to curl downwards. Easily controlled by spraying with a suitable insecticide.
Earwigs - night creatures which feast on the sepals and young leaves. These can be controlled by dusting with an insecticide dust but this can be as unsightly as the damage caused. Place half a grapefruit rind at the base of the plant and they will cluster here during the night, to be disposed of at leisure.
Slugs & Snails the bane of the gardener's life, responsible for wholesale slaughter of young emerging shoots. Control with slug deterrents, biological controls or a light application of slug pellets.
Mildew this generally appears on poor starved plants although some plants are more prone than others. It can be controlled by spraying with a systemic fungicide and paying attention to watering and feeding.
Clematis Wilt The most devastating disease affecting even healthy well grown plants causing sudden collapse just as the buds are about to open. Whilst there is no cure a drench with fungicide at monthly intervals during the growing season does seem to act as a preventative. If, despite this the disease does strike out the plant to ground level then again drench the plant with a fungicide. Provided deep planting was carried out shoots should appear at ground level, even several months later.
Nurseries and other suppliers
You should be able to obtain these Clematis, suitable containers and the necessary supports from most good garden centres throughout the country. Just a few of the specialist Clematis nurseries are listed below :
Ashwood Nurseries Ashwood Lower Lane, Kingswinford, West Midlands, DY6 0AE
Peveril Clematis Nursery, Christow, Exeter, Devon EX6 7NG. Barry Fretwell's nursery is now closed but the site is an invaluable list of cultivars Barry bred.
Priorswood Clematis, Priorswood, Widbury Hill, Ware, Herts. SG12 7QH
Taylors Clematis Sutton Road, Sutton' Askern Doncaster England DN69JZ Tel: 01302 700 716 Monday - Friday 8am to 10am
Thorncroft Clematis Mail order only now Peter Beales Roses at Attleborough now stock a good range of Thorncroft Clematis in their newly refurbished plant area. To check availability at Peter Beales Roses please call on 01953 454707
The information given in this Fact Sheet is provided in good faith. It is however of necessity general information and advice on the topic. Howard Drury will not be under any liability in respect of the provision of such advice and information and you are strongly advised to seek independent advice on any particular gardening problems or queries you may have, preferably from experts who can (when appropriate) inspect the problem before providing advice.