Planting clematis is an ideal way to add vertical interest to your garden. This plant is a mass of spectacular blooms and depending on the cultivar, flowering can begin in spring and last into fall. Clematis falls into three groups, A, B, or C. Basically this grouping indicates the kind of spring pruning you will need to do in order to get the plant to bloom more vigorously.
Group C clematis is the easiest to prune as they bloom on new wood. These plants are cut about a foot from the ground just above two strong buds. These buds will develop into new vines. Jackmanii, a group C clematis, is a 10 foot vine with deep purple 4 inch blooms that cover the entire trellis in early summer. I highly recommend this clematis as it is one that proves to be very successful for many gardeners.
Group B clematis bloom on old and new wood, thus pruning is done by taking out broken or damaged vines as well as thinning out areas that are very tangled. These cultivars do well growing alongside a climbing rose as their pruning requirements are very similar. A popular cultivar in this group is Henryi, which grows 8 to 10 feet tall. The flowers are large and white in color.
Group A clematis blooms early in spring and needs minimal pruning as the plant doesn’t die back in winter. This clematis blooms on old wood, thus any pruning that is done to tidy up the vine should be done after the vine flowers. Main stems should not be cut, only the tips of the branches. A popular cultivar in this group is Armandii, which blooms with white flowers on 10 to 15 foot tall vines. It is often difficult to grow this clematis in northern climates as the vine may not survive during severe cold winter weather.
To help ensure good growth, clematis should be planted in rich organic soil. Be sure to prepare a generous planting hole for your clematis. Incorporate compost, well rotted manure, or leaf mold into the planting hole. This will help hold moisture in the soil as well as providing optimum growing conditions for the expanding root system. Plant your clematis with two sets of leaf nodes slightly below soil level. This will encourage the plant to send out more vines which will make for a fuller plant. Clematis like their head in the sun and their feet in the shade which simply means that the root system need to be kept cool and moist with adequate mulch, yet at the same time sun exposure is needed to provide for optimum blooming. A yearly feeding of a 10-10-10 fertilizer right after pruning is also beneficial.
Clematis needs a trellis or some kind of support to allow for its varying heights. Remember that clematis climb by twisting leaf petioles which grow from the vine. A trellis support over ¾ inch in diameter is too big for the leaf stem to grasp. Nylon fish line is an excellent method of getting a clematis started up a post or larger trellis. Attach the fish line to your trellis but also make knots in the line at varying intervals. This will prevent the leaf stems from slipping down the line.
Be patient with your newly planted clematis while is develops its root system. It may be a few years before you see a profusion of blooms. It is definitely worth the wait. Until next time… happy gardening.
Nina Binkley, UW Extension Master Gardener Volunteer