How To Plant And Care For America’s Favorite Vine
Support your local clematis
Some clematis climb only a few feet, but some of the more vigorous ones can stretch out 50 feet. That’s why you’ll want to plant all but the shrubbiest varieties next to a trellis, arbor or other support. The twining tips will wind their own way up strings and fencing, but you’ll have to train them or tie them up poles and other large or smooth surfaces.
Clematis flowers are most often flat, but some varieties have urn-shaped flowers while a few are trumpet-shaped. Get some extra ornamental mileage out of your plants by cutting a few clematis blooms for indoor flower arrangements. Or float cut clematis flowers in a bowl of water after burning the ends with a match to lengthen their life.
Moving back outside, clematis are at their best when used as a light, airy, colorful screen planting, such as on a deckside trellis, on a porch railing or growing up and over a pergola or archway. They’re also great for growing on fences or up light poles to add vertical color to the front yard. (They’ll hide that rusty light pole of yours so long as you give them something to climb on, such as string or netting.) Clematis can even be grown intertwined with climbing roses, grown up trees, grown sprawling out of hanging baskets or grown to ramble as a groundcover.
The ideal spot for a clematis is in moist, well drained soil that gets sun for at least half the day — six hours or more, although some dappled shade in the hottest part of day is fine.
You’ll find some differing opinions on exactly how to plant them, but in our clayey, central-Pennsylvania soil, we suggest “babying them” a little. Dig a deep and wide hole (about 2 feet deep and 3 feet wide) and improve the soil with one-third part peat moss, rotted manure, mushroom soil, compost or other organic matter to two-third parts of your soil.
Plant your clematis slightly BELOW grade (about 2 inches deep), backfill and water well with a fertilizer high in phosphorus (the middle number on the formula). Note that this is different than the advice for just about all other shrubs and vines. The main reason for the below-grade planting is that it encourages the formation of more new shoots in the event stems are gnawed off by rabbits or rodents or killed by wilt (more on that later).
After watering, cover the ground with about 2 inches of mulch, being careful to keep the mulch a couple of inches back from the bark to avoid bark rot.
It’s also a good idea to erect a small protective cylinder of chicken wire or hardware cloth around your young clematis to prevent animal damage.
Clematis takes awhile to get settled, so don’t be alarmed if the growth isn’t tremendous that first year. Just make sure you keep the plant well watered — at least one deep soaking per week to the bottom of the root ball.
Clematis are fairly heavy feeders, so feed them monthly up until flowering time with a balanced fertilizer. Or you can feed them in the spring with an organic or slow-release fertilizer. Clematis like near-neutral soil (a pH of about 7), so add lime if your soil is on the acidy side.
While clematis plants like sun, the roots prefer to be cool and moist. Maintain that 2-inch layer of mulch at all times or plant a shallow-rooted groundcover around them (such as sweet woodruff, creeping phlox, candytuft or veronica). Heading into winter, it also helps to add a little extra root protection with a thick layer of straw or shredded leaves.
To encourage fuller plants, prune all varieties back to about 12 inches (or to two to three buds) the first year. From then on, pruning varies depending on the variety. For pruning purposes, clematis falls into three groups.
The first group blooms in early spring on buds formed the previous year. These should be pruned immediately after blooming but no later than July. Remove shoots that have bloomed, thin out dead or weak branches and head back branches if you need to control the size. Do not cut back into the main branches, though.
The second group consists of the large-flowered hybrids that mostly bloom in mid-June and sometimes again in late summer. Prune these in late winter (late February or March) by removing dead or weak branches and cutting back the remaining branches to the topmost pair of large, plump green buds.
The third group consists of the late-flowering types, which bloom on the last 2 to 3 feet of that season’s new growth. Prune these back hard in late winter by cutting back all branches to 2 or 3 feet.
If you’re not sure which type you have, give us a call.
Watch for wilt
One of the few threats to clematis is a disease commonly called “clematis wilt.” This fungal disease causes vines to turn brown and die. New shoots usually will sprout, but it detracts from what should be season-long foliage.
The large-flowered hybrids are most susceptible to wilt, so choosing early and late varieties (such as the species alpina, macropetala, montana, viticella or paniculata) can help prevent it. Having light, high-organic soil and using kelp meal as a fertilizer also seem to help prevent it.
If wilt hits, remove all infected plant parts and the infected mulch. Drench the soil with a fungicide until new growth starts.
Clematis also sometimes is infected by powdery mildew, another fungal disease that causes a white, powdery spotting on leaves. It also can be treated by a fungicide spray.
On the bright side, bugs seldom bother clematis. It’s one of the few plants that even Japanese beetles hardly ever touch.