Fact Sheet 341/2015
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 1.
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
Any of te Raymond Evison Patio Clematis collection, these are very dwarf, repeat flower and are more tolerant of hotter positions than many Clematis.
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 18" deep and 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.
Good drainage is imperative. Make sure the container has plenty of drainage holes and then cover the base with a 2" layer of broken pottery and small pebbles. Use a John Innes No.3 compost and plant the Clematis with the root crown about 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.
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. The Flowerbelle and Cocoon types of support (as shown on the programme) are made by Witchester Wood Design, Mold Industrial Estate, Wrexham Road, Mold, Clwyd, telephone 01352 752555. These supports will also be on sale in garden centres.
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.
The Clematis in the top list 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.It remains uncertain how to prune the Patio Collection varieties other than tidying them up as their parentage is complex and the fact they flower over a long period during late spring and summer.
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 for ornamentqls that states kills greenfly.
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 more 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.
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 :
Caddick's Clematis Nursery, Lymm Road, Thelwall, Warrington, Cheshire WA13 0UF.
Peveril Clematis Nursery, Christow, Exeter, Devon EX6 7NG. No mail order
Valley Clematis Nursery, Willingham Road, Hainton, Lincolnshire LN3 6LN
Priorswood Clematis, Priorswood, Widbury Hill, Ware, Herts. SG12 7QH
Pennells Nurseries, Newark Road, South Hykeham, Lincoln, LN6 9NS.
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.
(C) 2016. This material has been produced by Howard Drury and must not be reproduced in part or full physically or electronically without the written consent of Howard Drury, Kings Heath Birmingham, B13 0SJ. The only exception be to print a single copy for personal use from a downloaded file as part of the drurys website. Visit www.thedrurys.com or email for more information