How to Grow Series
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Clematis is one of my most favorite perennial flowering vines of all time. There must be over 400 varieties to choose from and they are readily available at garden centers and home improvement stores all over the country, not to mention online.
Though clematis have a reputation for being hard to grow, they are really pretty easy to take care of once you have chosen the correct site and prepared the soil properly. After that is done, they only need about as much maintenance as the rest of your garden.
See photos of clematis from my garden here.
There are three types of clematis: spring flowering, continuous flowering and summer flowering. Sometimes they are referred to as Group 1, 2 and 3, or A, B, and C, respectively. The spring and continuous flowering varieties are generally less hardy in colder climates, but summer blooming varieties are generally cold hard to zones 5 and 4. Check the label of the one you are interested in to know for sure.
Most clematis have vines that run 1o-12 feet tall, but as with most plants these days, there are dwarf varieties that are less than 6 feet tall as well. Choose the one that is best for your location and situation.
Clematis are not heavy plants, so they don't need a heavy-duty support, but they do need a support of some kind. Make sure your trellis has a small profile so that the vines can easily wind themselves around it, such as with coated wire, chicken wire, hardware cloth, copper pipe lamp posts or wooden trellises with supports about one inch wide or less.
Clematis require six or more hours of sun to bloom well and they like fertile, well-drained, moist soil that is heavily mulched. While they need sun to bloom, they also like there roots cooler, so mulching is essential.
Clematis don't like competition from other roots as the dominant plant will absorb all the nutrients from the soil before the clematis has had a chance to do so. That being said, many people plant clematis with shrubs and use the shrub as the trellis and to help keep the roots of the clematis cooler. You just may need to fertilize more often. You may want to grow clematis with roses as they require very similar needs when it comes to fertilizer.
Clematis also prefer a more neutral soil, so if your soil is on the acid side, top dress soil with lime once or twice a year to help keep the soil on the neutral side. You may have to perform a soil test every year before you apply the lime so that you know how much lime you need to apply.
Spring and Fall are the best time for planting, but you can plant container grown clematis in summer, provided you are mindful of your plants getting enough water during hot dry spells. Since their roots are not established yet, they may require watering every day during extreme heat and you may need to offer temporary shade as well. Bare root plants are generally planted in Spring only.
When it's time to plant your clematis dig a hole that is at least twice the size of the root ball of the plant you have and about 6-12 inches from the trellis base. If you are using a shrub as the trellis, use the 12 inch guideline.
Add lots of compost and composted manure to the planting hole and mix it with the existing soil. If you don't have your own compost pile, many home improvement stores and nurseries carry bags of compost mixed with manure. This is a great alternative if you don't have your own. If you can get organic, even better, as not all compost is created equal and there have been studies lately of compost actually being deadly because of too many chemicals used on the material that is being composted.
When planting clematis, you want to plant the crown of the plant two inches below the soil surface or at least two sets of leaves below the surface. This is opposite of what you are used to doing with other perennials. Planting the crown below the surface will allow the vine to grow a stronger root system.
Once your clematis is planted, water it well, fertilize (see fertilizing section below) and then mulch heavily with a 3-4 inch layer of an organic mulch. Water again so the mulch gets saturated, which will help keep the soil below moist and cool.
You will need to use something to loosely tie your stems to the trellis you have chosen to help guide the plant upwards. I tend to add a new tie every couple feet or so as the plant grows up until it can twine around the trellis on it's own.