12th February 2015 Clematis Pruning Masterclass

We did Clematis pruning today of the Group 3 kind, which are the types that flower after early summer on new wood.

There were 88 different varieties on the trials field - late, large flowered ones from the Lanuginosa Group - bred from C. lanuginosa directly or indirectly and the Jackmanii Group - which is a cross between C. viticella and a member of the Patens Group. Because of overbreeding, hybridization &/or lack of information of parentage it is difficult to tell if a Clematis belongs to either one of these groups. Flowers vary from single, semi-double and double, erect, horizontal, semi-nodding, flat to bell shaped, and the colours range from white, pink, red, purple, blue.

Clematis were first recorded in the UK in the 16th century. Most of the breeding frenzy occurred in the 1850s when plants were brought back from China & Japan. George Jackman who bred the famous C. Jackmanii was a Surrey local and had his nursery in Woking. Also because of over-breeding the fungal disease Clematis wilt Phoma clematidina is a problem, though apparently not as common as people think, but the Trials bed is rife with it and also has Clematis chlorotic mottle virus - new to Europe. The former affects the plant above ground, so it is possible to cut down in time to stop it from travelling down the stems and affecting the roots, plus with good hygiene - it would reshoot new shoots disease free. This is why here they plant them two buds down in the ground to increase the chances of recovery if affected. This also meant we had to fastidiously dip our secateurs in Vircon everytime we pruned a new cultivar, preferably a new plant of that cultivar (there were usually two to a station). Some cultivars are wilt resistant like Perle D'Azur.

Pruning is simple, we just cut to a strong bud (half a cm above a bud), 15 - 30cm above the soil (internode dependent), and cleared the cut offs and dead leaves as best as possible - putting them in plastic bags to be tied in string, taken on a trailer and specially discarded (burnt).

Some of the ones I pruned were C. Perle D'Azur and C. CADDICK'S CASCADE 'Semu' (Photo 2).
Photo 2.

Because of their tendency to grow tall and flower at the top, these are pinched out as soon as it has new growth four nodes up, to stimulate them to branch out and flower lower down too, up until Chelsea time. The supports aren't ideal (bamboo canes, chicken wire, stabilised further by thicker wooden posts) - but as trials are not paid to be done, this was the cheaper solution they came up with. 

They are best grown with cool moist (well drained) bottoms and hot sunny tops. This site is very exposed (South Facing). They are mulched and are left as much as possible - but I did wonder if they should water more though to make up for the fact that they are not well sited.

They can be propagated several ways - via soft wood cuttings, layering the serpentine way, division, nibbling (taking a small section away from the clump - 'an amateur method') and seed. Cuttings are taken spring to late summer, and layering - late winter to spring.