Enjoy clematis up close in containers
Why settle for clematis scrambling up a far-off fence or a distant obelisk when you can enjoy these spectacular blooms up close — right on your deck, patio or balcony! Even gardeners in USDA cold-hardiness zones 4 and 5 can grow these showy vines in containers year-round if they follow the tips from Cindy Tibbetts, owner of specialty clematis nursery Hummingbird Farm in Maine.
Getting started with growing clematis in containers
To grow great-looking clematis in a container, don’t skimp on pot size. Cindy recommends using a 24-inch-diameter container (larger is fine too) so the potting mix doesn’t dry out too quickly and the roots have lots of room to grow.
Fill containers with quality bark mix
Cindy fills her containers with Happy Frog® Potting Soil. This blend has big bark chunks that ensure good drainage and air circulation, both essential for preventing root rot, which can be a problem for clematis in containers. But any brand of mix with bark will work. Compact varieties work best in Cindy’s containers — those topping out at 6 feet tall or less are easier to manage.
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Clematis care
Maintenance during the growing season is simple: Water and feed. Container-grown clematis can dry out more quickly than their counterparts in the ground, so check the potting mix regularly, especially when temperatures rise in summer. You’ll know the container needs watering when you stick your forefinger in the potting mix up to the first knuckle and it’s dry.
Feed with liquid plant food while blooming
While clematis aren’t usually heavy feeders, those in containers need more attention because watering pushes the nutrients from the potting mix quickly, sometimes before plant roots can access them. Cindy recommends using any liquid plant food according to label directions every week or two while plants are blooming.
Check soil pH
One year, some of the clematis developed interveinal chlorosis — a yellowing between the veins as a result of nutrient deficiency. A soil pH that’s too alkaline is often the problem. But Cindy discovered that the well water at Hummingbird Farms had a pH of 8.2. If the pH is over 6.7, iron and magnesium can’t be taken up by the plant, so yellow leaves develop. She solved this with a water-soluble acid formula plant food, which helped lower the pH, and now her clematis can take up nutrients properly.
Prune clematis roots and stems every few years
After two or three years the bark in the potting mix tends to break down, so it’s a good idea to take everything out of the pot, add more mix and replant your clematis. This provides fresh nutrients and keeps drainage sharp. When Cindy unpots the plant, most of the potting mix falls away. She takes this opportunity to do a little root pruning, which ensures plants can grow in the same container for years.
To do this, she teases out the roots and keeps an eye out for any that are broken or diseased to cut away. Her rule of thumb is that if the roots won’t fit neatly back into the pot without winding around, she cuts them back just enough to get it back into the container.
Tips for pruning clematis
Prune the clematis stems just like you would if it were growing in the ground. The varieties in the gallery below are all part of pruning groups 2 or 3.
- Cut group 3 clematis to within a foot of the crown in late winter or early spring.
- Clean up group 2 clematis by removing broken stems and shaping the vine (trim long stems or reposition those that are going where you don’t want them to).
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Try these clematis varieties in containers
The varieties above are some of her favorites and look spectacular throughout the nursery’s seating and display areas. Most of these are compact varieties that will perform well in containers; find details for each below.
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A) Sarah Elizabeth™ Clematis hybrid
Pale pink single flowers with maroon anthers from late spring to fall; 4 to 5 ft. tall; pruning group 3; cold hardy in USDA zones 4 to 9 -
B) Guernsey Flute™ Clematis hybrid
Large 5-in. white flowers with red anthers from late spring to fall; 3 to 4 ft. tall; pruning group 2; cold hardy in USDA zones 4 to 9 -
C) ‘Piilu’ Clematis hybrid
Double 4- to 5-in. two-tone pink blooms in late spring, single flowers until fall; 4 to 6 ft. tall; pruning group 2; cold hardy in USDA zones 4 to 9 -
D) Bourbon™ Clematis hybrid
Single 5-in. red-purple flowers in late spring to fall; 4 to 6 ft. tall; pruning group 2; cold hardy in USDA zones 4 to 9 -
E) Tranquilité™ Clematis hybrid
Star-shaped flowers have overlapping lavender petals that fade to a white center in late spring to fall; 4 to 5 ft. tall; pruning group 3; cold hardy in USDA zones 4 to 9
Clematis plant source
Hummingbird Farm, hummingbirdfarm.net, 207-224-8220
Tips for overwintering clematis in containers
Getting container-grown clematis through the winter can be tricky if you garden in zones 5 or colder. Over the years, Cindy has tried lots of different ways to get clematis in containers through winter. Here are the tips she’s learned from hard-won experience.
Container materials matter!
Gardening in USDA zone 5, where winter temperatures regularly drop below freezing, Cindy learned an expensive lesson about different types of containers when several ceramic pots planted with clematis and left outdoors cracked and broke. Now she plants in wooden containers, which are both sturdy and drain well. Resin containers are another reliable option for cold climates. Plastic pots are more of a temporary fix — they tend to get brittle and crack after a few years. For gardeners in zone 8 or 9, ceramic pots are an excellent choice, as they won’t face the destructive expansion and contraction that comes with freezing temperatures.
Plan for protection
Initially, Cindy left container-grown clematis outdoors all winter without protection. While most survived, the melting spring snow sometimes kept the potting mix cold and wet for too long, causing root rot.
Two easy ways to overwinter clematis in containers
1. Overwinter clematis grown in containers in a garage or shed
Now she has a better system, so all the clematis get through winter. In late fall Cindy hauls the container-grown clematis at Hummingbird Farm into the greenhouse. (An unheated garage or shed would work too.)
The best part is that you can basically forget about them until spring. No watering or fussing with lights needed — the foliage turns brown like the one in the illustration above and plants go dormant anyway. When spring arrives and the threat of frost is past, drag them outside, water and do whatever pruning is required for that variety.
2. Protect container-grown clematis in place
If you can’t move a large container into a shed or greenhouse, try this tip from one of Cindy’s customers:
Cut the stems back to 6 to 8 inches tall in fall after it goes dormant. Then place a 10-inch diameter (or slightly larger) nursery pot over the stems and drape a piece of heavy plastic sheeting, the kind you find in the paint department at the hardware store, over the whole setup. Avoid a porous tarp, as you need it to shed water.
Secure the plastic on the ground with a few bricks or stones to keep everything in place through winter. You can see how it all goes together in the illustration above. The overturned nursery pot ensures that the plastic sends snow and ice melt to the ground and away from the plant. In spring, remove the covering and watch your container-grown clematis take off.
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