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Clematis are beautiful flowering climbers, and can be quite easy to grow given the right conditions. BUT – there are a few tips to know and which will help you avoid disappointment.
Growing Conditions
Clematis require a well drained soil with some organic matter in the soil. You want a neutral to slightly alkaline soil – if your soil is acidic, add a bit of lime. Clematis grow best with the roots in a shaded, cool environment and the vine exposed to the sun, with a few exceptions they need a minimum of 6 hours of sunlight a day. Ideally, clematis prefer a position with some afternoon shade and full morning sun, protection from strong hot wind helps too. To improve the soil before planting, mix in a generous amount of compost and manure. When you have planted your clematis, mulch the roots with a thick layer of mulch. Even small plants in front of the clematis will help to shade the roots.
Clematis require constantly moist soil to grow well, using drippers or soaker hoses to irrigate, rather than sprinklers or hand watering is preferred. That said – do not drown them – that is a sure fire way to kill them.
Organic fertiliser should be applied at the recommended rate through spring, summer and autumn.
Planting
This is one of the areas where clematis are a bit different from most.
Dig a hole a minimum of 10cm deeper than your potted clematis. Spread some slow release fertiliser into the base of the hole, and cover with 5cm of soil. Improve the removed soil with compost and fertiliser. Now, GENTLY ease the plant out of the pot and into the hole, remembering that at this stage in its life, every bit of the clematis (roots, crown stems) are easily damaged. You want the top of the potting mix to be about 5 to 10cm below the natural soil line – what you are aiming for is to have the first set of leaves on the stems to be just buried (pluck these leaves off). By planting deep, you are encouraging the dormant buds below the soil line to grow and form new stems – this gives you a strong multi stemmed plant. Back-fill the hole and tamp down gently but firmly. Water in well. Now mulch, but keep the mulch 5cm away from the emerging stems.
Training
Your clematis will need support to climb up, it is a twining climber – in other works, it isn’t like ivy, clamping itself onto a structure and sticking, clematis twines its way along a support structure. This can be trellis or wire against a wall, or you can train Clematis through taller trees and shrubs. Be careful when tying up Clematis canes because the stems are very brittle and easy to break or damage. If there is nothing to climb, the clematis will stop, so you can manipulate where you want it to grow by either providing, or not providing, an underlying support structure (wires, grids, trellis or even other plants).
Pruning
Conventionally clematis are divided into 3 groups.
Group 1 – Flowering on old wood, includes all the Clematis montana cultivars and a few others.
These generally only require pruning to keep tidy and remove old dead material. If you do need to prune, grab your secateurs after flowering is over in spring, remove old dead material and any week spindly growth. Cut away anything growing in a direction you don’t want, and if you feel the whole climber needs thickening up, cut back a bit harder to encourage thicker growth. If you prune early enough (before mid/late summer), the new growth should be mature enough to flower next season. Feed after pruning – pruning encourages new growth, and the plant requires food and water to grow.
Group 2 – Flowering on both last year’s and current season’s growth (old and new wood).
The trickiest ones to prune, if you are really worried, for the first few years, you can leave it until mid spring when the plant is really growing, and then cut out any dead and unproductive growth. As you get more confident you can prune in winter to good fat buds on strong stems and cut away the weak spindly stems. After the first spring flush of flowers, deadhead and prune lightly to encourage the second set of flowers which will appear in late summer. Don’t forget to fertilise, clematis are hungry plants.
One of the fascinating features of these climbers is that sometimes, the previous year’s growth produces double and semi double blooms and the current year’s produces single blooms.
Group 3 Flowering on current season’s growth (new wood)
These are possible the easiest clematis to prune. Clear out all the growth and prune back to a strong bud near the ground level. This can seem a bit extreme the first time you do it – but these clematis are vigorous growers and will grow rapidly the following spring. Make sure they have plenty of fertiliser in early spring to support this growth. After the first flush of flowers, deadhead and prune lightly to encourage the second set of flowers which will appear in late summer. Don’t forget to fertilise again, clematis are hungry plants.
Clematis may be propagated or thickened up by layering. Simply lie the stems down on the soil and hold the stems down with soil or small stones, leaving the nodes uncovered.
Growing your clematis in a pot
Yes, you can grow many clematis in pots – the dwarf and smaller growing clematis do well in large pots.
There are pluses and minuses to different pot styles. Un-glazed terracotta pots will definitely keep the roots cooler via evaporation, but that very evaporation means they lose water faster, so you need to keep a close eye on watering. Whichever pot style you use, it needs to be a minimum of 30cm in diameter and 50cm deep and only ever use top quality potting mix. Fertilise regularly, you can use liquid fertiliser, but it won’t be sufficient unless you use it very frequently. Avoid direct sunlight falling on the pots, it is important the clematis root zone stays cool.