A Gardener's Diary: Clematis makes the cut
I noticed that some of my clematis, overwintering in the greenhouse, had an early start. I had to search how to treat these lovely flowering vines and thought that it would be the subject of this week’s column. Some of the growing tips came from the internet and Gardens West magazine.
Every clematis should be cut back hard the very first early spring after planting (when you see leaf buds developing as your plant breaks dormancy, leave two sets of buds on each stem between your cut and soil level); following that, it should be pruned according to its grouping:
GROUP A clematis flower only on growth from previous years. Prune to cut out weak or dead stems as soon as they are finished blooming in May or June. Pruning later than June or very severely will result in fewer blooms the following spring.
GROUP B1 produces a heavy flush of flowers May to June on the previous year’s growth followed by a smaller flush of blooms in September on new growth. A light pruning in late February or March with variation in the length of the stems will produce a well-balanced plant.
GROUP B2 blooms continuously from June to September on both last year’s and current growth. For pruning purposes these varieties can be treated as group B1 or C and because of that work well in combination plantings with both these groups.
GROUP C blooms only on the current year’s growth, from early summer through to fall. Cut back plants in late February or March to two strong sets of buds on each stem as close to ground level as possible. If you want to grow a group-C clematis through a tree or have it flower above its normal blooming height, leave it unpruned.
Clematis benefits from an annual spring application of mulch to insulate the roots from heat, necessary for shallow-rooted vines that require cool roots. Whenever the ground is workable, clematis can be planted. Clematis need a cool, moist, deep root run, plenty of water until established and regular, balanced feeding. Dig a hole 45 cm (18 inches) by 45 cm wide and 45 cm deep, and cover the bottom with a good rich compost or well-rotted manure. A handful of bone meal mixed with soil is also beneficial. Add enough topsoil to cover the compost; now you are ready to plant. Place your well-watered clematis in the hole so that about 15 cm (six inches) of stem is below the soil line to encourage more stems to grow from the base. The more stems the plant grows the faster the coverage and the less susceptible the plant becomes to disease. Remove any leaves that grow beneath the soil level. Next, attach the stem to a support and consider planting a small shrub in front to ensure your clematis has a cool root run.
Generally, it is recommended to mulch plants to a maximum of 2.5 to 5 cm (one to two inches), which allows the free exchange of air and water and poses no danger of suffocating or rotting the plant’s root system. Clematis is an exception to this rule; it benefits from a deeper mulch of 7.5 to 10 cm (three to four inches), spread evenly along the drip line or 30 to 45 cm (12 to 18 inches) around the plant, making sure to allow a mulch-free space around the woody stem. Deeper mulch provides protection from heat for the roots and helps retain moisture during drought.
There will be another seed sale at the SENS meeting at Schubert Centre March 28 at 6:30 p.m.
For more information: 250-558-4556.
Jocelyne Sewell is an organic gardening enthusiast in Vernon and member of Okanagan Gardens and Roses Club, whose column appears every other Wednesday.