Nov 30, 2023 | Gardening Advice

Some of the most beautiful flowering plants we can grow in our temperate gardens are the Clematis (KLEM-a-tis), both vine and shrub forms. Clematis range from short growing perennials to vines reaching 30-50 feet. They have been hybridized since the 1880’s.

Clematis vines are perfect for growing on a trellis, porch, arbor or fence and the shrub forms are a focal point of the border. Most have abundant flowers and often silvery-gray seed pods which are perfect for drying. Clematis has a reputation of being finicky. Why must a plant so wonderful be such a challenge to grow? Often the fault is the gardener or nocturnal insects. Plant your Clematis where it wants to be — not necessarily where you want it. It is a plant that likes its head in the sun and its feet in the shade. Bloom is best with at least a half a day of sun.

Clematis like a rich, friable, deep loamy soil, well-drained, but constantly moist, a rare commodity in Maine. If you provide this soil most problems will be avoided. Dig a hole 18” deep and 18” in diameter, where roots from nearby shrubs and trees will not encroach. Fill the hole with a well mixed batch of peat moss, composted manure, a few handfuls of bone meal and cottonseed meal, sand and 1 cup of lime per plant. Smooth this off leaving the spot well crowned, so that the place where you will place the plant will be 4” higher than the surrounding ground. Make a hole large enough to hold the Clematis’ root ball. Set it so there are two or three leaf nodes below the surface — do not cover these until the lower portion of the stem has become woody. At that time fill in and cover the lower stem.

After planting, water thoroughly. Continue to water regularly through the growing season and in subsequent years. Place rocks at the base to keep the roots cool and moist. Provide a stake or other support for the stem at the time of planting. Injury to the weak lower stem spells doom. Fertilize in spring with 10-10-10 or with compost.

One of the most common causes of failure in newly planted Clematis is damage by insects. This almost always occurs at night. Cutworms, pillbugs (sowbugs) and slugs can chew into or through the stems. To avoid this damage place a protective collar around the Clematis when planting. A 1-2 gallon pot, with the bottom removed, placed 2-3” into the soil will really help. If insect damage occurs, despite these precautions, dust with an insecticide. A dusting is recommended because it doesn’t readily wash off and is visible. More is needed when you can no longer see it. Rose dusting powder containing both an insecticide and fungicide is an excellent choice. If you prefer to use a liquid, spray just before dark when the insects start to move about. Even insects just chewing on the stems can be fatal if the scar allows entry of Clematis Wilt, a disease which slows the flow of nutrients and moisture up the stem. This is often why an apparently healthy plant will suddenly wilt and appear to die. If this happens cut back the vine immediately and water with diluted fertilizer. The vine will probable survive if you planted it deeply. Do not prune, except to remove deadwood, the first two years. Thereafter prune to remove deadwood and tangled branches. Some Clematis bloom on new wood; these may be pruned in the fall (even to the lowest pair of buds). Others bloom on year old wood; these should be pruned after blooming to thin and shape. See Pruning Chart.

So remember — terrific soil, not too much heat or sun, and keep insects away. You will eventually succeed and have all your neighbors drooling. If you like them … tell them the secret, if not … let ‘em drool.

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