Blooming clematis are truly dramatic. Growing clematis can at times, be daunting. The secret is understanding the pruning type of clematis you have and when is the best time to prune your clematis.
Most nurseries recommend growing clematis in USDA zones 4 to 9.
"To prune or not to prune," is the most often asked question. Incorrect pruning in most cases will only delay flowering. However, improper timing of the pruning can cause the death of the plant. DON’T PRUNE IN THE FALL! Let your clematis stay unpruned and dormant until spring. Furthermore, if all varieties were left unpruned they would all flower very well. However, the flowers would not necessarily cover the plant as well as they otherwise could.
In colder climates where temperatures drop below 0°F foundation planting and mulch are required to ensure a long life for your clematis.
It takes about 3 years and lots of fertilizer and water for a vine to develop a root system that will produce a robust and productive vine.
There are 3 basic pruning types of clematis. These groups are labeled AB or C, or sometimes 1-2-3, by the nursery. Sometimes they are not. If your clematis isn’t labeled or you don’t remember, just make a few observations and it will tell you which type of clematis you have.
When does it bloom?
Does it bloom on new growth?
Or does it bloom on last year’s woody growth?
The best place to prune a stem is above two strong buds. These buds will quickly develop into new vines. Angled cuts are not necessary
Group A clematis doesn’t die back in the winter and blooms in early spring. This group typically requires only moderate pruning of the tips. Never remove the main stems. Since most of these blooms happen in early spring on old wood, wait to do most of your pruning after the main flowering has finished. Hard winters can sometimes kill back the tips.
Group B clematis typically produce large blooms on old wood in the spring, and then produce a crop of smaller flowers on new wood later in the season. Cut away broken branches, thin out congested areas to avoid a tangle of vines.
Group C clematis typically die to the ground over winter, or it flower are only at the top with lots of last year’s dead foliage and bare stems showing at the base. This is the largest group of clematis. There are a variety of different heights to select, with the tallest variety growing up to 20’.
To keep Group C clematis lush and full, cut all the stems to about 12” from the ground. This will leave 2 – 4 sets of buds per stem. Train the new vines onto a trellis and space these stems so the flowers will display at their best.
In general, if your clematis flowers early on old wood - i.e. the previous year's growth - they should be pruned after flowering, and then only to tidy up. If they flower in late spring and then again in late summer/fall, they should be pruned lightly in late winter/early spring depending on your location. If they flower in late June early July, cut them back hard in late winter/early spring.
Most clematis enjoy being exposed to at least 5 to 6 hours of sunlight daily. In hotter inland and canyon areas, planting pastel pink varieties in bright shade helps to minimize fading.
Once established a clematis need a cool, moist, deep root run, plenty of water and regular, balanced feeding. Clematis like early morning sunlight (east exposures) best.
Preparing the planting site is a critical step to insuring the longevity of your clematis. In heavy or clay soil, dig a big hole, preferably 24"x 24". In lighter or sandy soil, a hole 18"x18" will do the trick. Save only the best of your topsoil. Amend the soil as conditions dictate. Soil testing is recommended.
The plant needs alkaline soil and cool roots, which usually is accomplished with a little mulch. In soils on the acid side of the pH scale, you will want to add some lime to make it a bit more alkaline. If the soil is already alkaline, don’t add lime. A pH of 7 – 7.5 is ideal.
Add plenty of organic matter and mix in with the existing soil.
Always cut the container before planting your clematis. This minimizes the risk of damaging your plant when removing it from the container. Gently remove the clematis root ball from the container and plant it in the hole so that the base of the plant's stems are sunk 3" to 5" below soil level. This will encourage plants to send up more stems and you’ll have a thicker plant. Leave the original stake on the clematis for the first year to act as a support as well as a protection against accidental breakage.
Clean up the leaf litter in the fall around the clematis to help reduce fungal and other disease infections from carrying over to the next year.
Place a 3" - 4" layer of soil amendment or peat moss over the root zone. Keep the mulch 8" away from the stem to avoid stem rot.
Over-wintering protection: Clematis only needs a basic mulch cover on the crown after the soil freezes. Keep it moist before the ground freezes and it should get through the winter in good form.
Clematis are heavy feeders. In spring, once the clematis bud stems are about 2” long, start feeding them with a balanced 10-10-10 granulated fertilizer.
Clematis may need regular watering, especially during hot dry weather. Always water thoroughly and deeply during the hot summer months. Don't keep them too wet, especially in the winter when they're dormant.
Clematis need support to grow. This can be achieved in many ways. From growing them on an arbor to up a trellis, onto other shrubs, on a fence, or an obelisk, the possibilities are only limited by your imagination.
Clematis climb by twisting petioles or leaf stems. The vine itself does not twine. A good trellis should not be too large (larger than 3/4") or the leaf can't wrap itself around it. Nylon fishing line is one way to get a clematis to climb a light pole or arbor post. Tie a knot in the fishing line before stringing it, about every foot to keep the vine from sliding down the line as it grows.
Just as in growing clematis in the ground, the following steps for planting in a container are crucial. Select a container that is at least 18"x 18". Fill your container with potting mix leaving an adequate amount of space for a good watering basin. As stated previously, cut the container to remove the plant. Gently lift the clematis's root ball from the nursery container and plant it so that the stems are sunk 3" to 5" below soil level. Feed and water as if it were planted in the ground.
Clematis are susceptible to many fungi that can cause them to 'wilt' or turn black and these fungi enter the plant via the stem and work their way up. Although this is a very disappointing malady it is usually not fatal if you planted correctly. Carefully cut off all of the diseased parts of the vine and then disinfect your clippers with Physan 20. Dispose of all these diseased parts in a sealed plastic bag.
Ideally a clematis is best moved in early spring as soon as the soil is workable. If possible prep the new hole the previous fall. It should be substantially wider than the root ball you plan to dig up. Fill it with a good rich soil and a handful each of 5-10-10, lime, and superphosphate. Cut the top growth back to 3'-4' as clematis stems are so brittle early in the year that if they're any longer they'll snap. Plant in the new hole with the crown a little lower than it was originally and water in with a root stimulant to help minimize transplant shock. Water and fertilize regularly during the growing season.
Can I take a cutting from my friend's clematis?
Yes, you can root clematis cuttings. There are many books on propagation and it would be a good idea for you to borrow one from the library because it is rather lengthy to explain.
Here are a couple of tips for propagating clematis from cuttings: take the young shoot in the summer months and dip it into a rooting compound and also place it in a sterilized planting medium. Keep the soil evenly moist and then plant in the desired location towards the end of the summer. Read more about clematis propagation
Should I cut off the seed heads?
Yes, if you want more flowers. No, if you like the decorative aspect of the seed heads.
Why are my leaves turning yellow?
Yellow leaves can be a symptom of over watering or a mineral deficiency. Clematis need regular watering but it is important not to let them become waterlogged. Clematis are heavy feeders. The American Clematis Society endorses Gro-Power Fertilizer because it is an organic soil conditioner as well as a fertilizer and it contains the necessary minerals to keep clematis healthy.