Pruning climbers

Garden lovers often ask themselves whether and how to prune climbers. I think it’s worthwhile to explain what the reason behind the pruning is so that you may adjust it to our needs and obtain the best results.

The purpose of pruning is:

• to encourage branching. Shortening the stems by 1/3 to 2/3 of their length will encourage the apparition of new shoots from the buds left at the base. This type of pruning is particularly important in the first 1-3 years, when you create the strong base of the plant.
• to remove straggly growth. Cutting out the excessively twiggy stems that reduce light and air penetration into the plant centre will improve your plant’s health and looks. Pinching the growth back from gutters, windows, doors and from anywhere where it may disturb other plants will help you keep your garden tidy, which is especially important in case of growing vigorous climbers in a small garden.
• to improve the phytosanitary conditions. Cutting out any dead, diseased or damaged stems will prevent the spread of diseases from plant to plant.
• to encourage flowering and setting fruit. Some climbers, such as wisterias, Campsis or summer-flowering clematis, benefit from hard pruning. It may also accelerate and ensure a good fruit crop of Actinidia.
• to rejuvenate. Every 3 to 6 years you can remove some of the oldest branches to encourage more young and healthy growths in the next season. It is advisable to carry out this type of pruning in case of Clematis, Lonicera, Ampelopsis or Menispermum canadense.

If you have plenty of room in your garden, you may reduce the pruning of the majority of climbers just to a branching and a phytosanitary one, and let your plants grow in an otherwise unrestrained manner. Nevertheless, most gardens will benefit from cutting out any excessive growth at least once a year. When a climber growing against a wall reaches the height of the roof, the growth control becomes particularly important to prevent damage it may cause to the roofing or gutters.

Use a sharp tool (for instance a pair of secateurs), and make an angled cut 0,5 – 1 cm above a bud or a fork (fig. 1). Avoid cutting in the middle of the fork and leaving a stub, as it will anyway die back to the closest bud, impede healing and make the plant susceptible to diseases. In case of cutting a thick branch, cover the wound with some paint that will facilitate the healing. The best option is to buy a special product (e.g. Funaben), but you can also prepare it yourself by adding a fungicide, e.g. “Topsin M” to emulsion paint to obtain 1% solution.

The best season for pruning most climbers is between the end of February and the beginning of April, but there are many exceptions to his rule. Aktinidia and Vitis start their growing season very early, and therefore should be pruned in late January to February, before the juices start to circulate. Otherwise they will bleed and the plants will get weaker. If you miss this time, it’s better to wait with your pruning till June. Some climbers require special pruning regimes.

Actinidia. If you treat it as purely ornamental plant you can leave it to grow freely and only cut out straggly growth and all stray stems. Otherwise, if you want to ensure the best fruit crop you should train and prune it specially. Devote the first 3-4 years to forming your plant, as actinidias are long-lived and can grow for even up to 50 years. Remove all straggly growth in summer. Choose the strongest side shoots and tie them in to horizontal wires. In August, pinch back the tips of these stems to encourage branching and setting flower buds. At the end of winter you can repeat the trimming, shortening further the stems, but be sure to finish all the pruning before the end of February, as otherwise the plant will bleed. In commercial plantations Actinidia is usually trained along a T-shaped trellis (fig. 3). In amateur cultivation the easiest way to do it is to train Actinidia along the wires either stretched between posts, against a wall or a fence (fig. 4).

Wisteria should be left to grow in an unrestrained manner for the first 2-3 years to let it root and strengthen. In subsequent years, prune it hard to encourage the setting of flower buds. These develop in early autumn, which is why the basic pruning should be carried out in summer (late July-early August). Prune the majority of new shoots down to the 4th leaf from a main branch, leaving uncut only the stems needed for forming the shape of the plant. You may repeat the pruning in early spring, by cutting out any dead, very thin, or unneeded spurs and shortening any side shoots to 2nd-3rd bud above the base. If, despite this pruning the plant hasn’t started flowering and is still growing very abundantly, you may try trimming the roots. In February or March, dig the spade vertically into the ground around the plant, 30-60 cm away from the base.

Clematis. In the first year, prune all Clematis down to 30 cm above the ground to encourage new shoots to develop from the base. Alternatively, to achieve a similar or even a better effect, you can spread the stems on the ground and cover them with pine bark, just as you did when you planted your clematis. It will strengthen the plant, and therefore promote more abundant flowering and make the clematis more resistant to diseases. In subsequent years, the pruning depends on the variety and the time of blooming (cf. the last column in the plant encyclopaedia and the fig. A and B). In general, we divide clematis into 3 pruning groups which, for the sake of simplicity, we’ll number 1 (minimal), 2 (light) and 3 (hard).

Group 1 (minimal) – It includes clematis that flower in spring on old wood (e.g. Clematis montana and the cultivars from the Atragene Group). They needn’t be pruned at all, but if you need to cut them back to reduce them to their allotted space, do it only after they have stopped flowering and cut them down to a height that suits you but usually not lower than 1 m above the ground.

Group 2 (light) – It features the majority of large-flowered clematis, especially those that flower early in the season (first flowers appear on old wood in May or early June), and then have a second flush of flowers on new growth. Prune all the stems down to more or less the height of 100 to 150 cm above the ground (the younger and weaker the plant, the less you should prune it). This is also the safest way to prune your clematis if you don’t know which group it belongs to.

Group 3 (hard) – Clematis that flower from the end of June to July on current year’s growth, e.g. the cultivars from the Viticella Group and all large-flowered late-blooming varieties should be pruned hard. Cut the stems to the 2^nd-3^rd pair of buds, 20-50 cm above the ground. This is also how you prune vigorous, summer-flowering cultivars from the Tangutica Group if you want to reduce their growth. In case of perennial Clematis (e.g. from the Heracleifolia or the Integrifolia Group) and the cultivars from the Texensis Group, cut any dead stems near the base of the plant, and the rest of the growth 5-10 cm above the ground.

Honeysuckles (Lonicera). After planting, you should cut all the stems to 1/3 of their height to encourage development of strong side shoots at the base. Choose 2-4 the strongest stems that will form the base of the plant and remove all the rest. In subsequent years, honeysuckles that flower on previous year’s growth (e.g. Perfoliate Honeysuckle or Tellmann Honeysuckle) should be pruned lightly, just to remove any weak, dead or damaged stems or simply to reduce the plant to the allotted space. Every 5-6 years a hard, rejuvenating pruning is recommended. Honeysuckles that flower on new growth (e.g. Japanese Honeysuckle and its cultivars or Goldflame Honeysuckle) can be hard pruned in early spring without the fear of losing the flowers.