116 3rd St SE
Cedar Rapids, Iowa 52401
Family lore has it that Wanda Lunn planted her first iris in her grandmother’s garden when she was 3. She’s been hooked on gardening ever since.
Lunn grows hundreds of irises, lilies, peonies and other perennial flowers on her nearly half-acre lot in Cedar Rapids. When she began to run out of space for flower beds, she decided to grow clematis, a climbing, woody vine available in a wide variety of colors.
“If you’re thinking clematis, think vertical. Most of the clematis are climbing, and they can cover any structure in your garden,” said Lunn, a Linn County Master Gardener, who taught others about the special beauty of this flowering vine in an online webinar Feb. 20 as one in a series done in partnership with Indian Creek Nature Center and the Iowa State Extension and Outreach Linn County Master Gardeners.
There are three types of clematis, categorized by bloom time: early summer, midsummer, or fall. The type also lets gardeners know when to trim back the vine. Most clematis plants quickly grow after they become established. While there are 300 species and more than 3,000 cultivars of clematis, most cannot be found in the Corridor, Lunn said.
Choosing a new clematis
How tall they’d like the vine to climb is the first thing a gardener should consider when choosing a clematis. Most clematis grown locally are in the 6- to 12-foot range. Some, like Sweet Autumn, can grow up to 20 feet and can be too heavy for some structures. Sweet Autumn’s long vine is covered with a profusion of white, sweetly scented blooms in September.
“But she is a monster. I’ve seen her take a shed down,” Lunn warned.
Next, decide on a color. Clematis come in a wide range of hues, from jewel-toned purples to pale pinks. Yellow, red and burgundy are less common. Blooms range in size from unusual tiny, 1-inch bell-shaped flowers to huge flowers 8 inches across. You can intermingle clematis to create a rainbow effect. Just make sure to keep the roots about 24 inches apart, Lunn said.
A sturdy root system is necessary for a newly planted clematis’ survival. Lunn advises the following when selecting a new vine: Turn the pot upside down and look at the roots. If there is a lot of dirt and not many roots, it will die. Look for heavy, fibrous white roots. If you find a clematis you love but the roots are skimpy, leave it in the pot and water it well for a couple of weeks, then check for roots again.
If you’ve purchased a bare root plant, soak it in a bit of water for a few days.
“It will plump up the roots and get them all ready to get going,” Lunn said.
How to plant a clematis
To plant a clematis in the ground, dig a hole twice as deep and double as wide: the plant needs loose soil. You can place the plant 2 inches or 3 inches deeper than it was in the pot. Like a tomato, clematis will keep sending roots out from the stem when planted deeper, Lunn said.
Don’t cut the roots: gently tease them with a fork to ease them apart. Fill around roots with soil and peat moss. Water it well to remove air pockets and tamp the ground to avoid root rot.
Lunn uses a 10-10-10 dry fertilizer in early spring and late fall on all plants in her garden. “It’s slow and dry and feeds the roots, not the green growth,” she said.
To divide a clematis, dig up the entire root. Within the major root mass, you’ll see stems with root systems. Tease the roots apart, soak in water, then plant in pots just big enough to fit the root system. Water thoroughly. Plant outdoors after new growth appears.
Tips for all clematis
Now is a good time to plant clematis. But don’t plant new clematis in early spring: wait until after the average last frost date, or the newly planted vine will die. Master gardeners note that it’s about May 15 in this area.
Pots allow gardeners to grow the vine in an area short of space. Lunn advised adding gravel or something heavy to the pot to keep it from tipping over. Clematis are happiest in pots that don’t allow too much room. You’ll have to water the thirsty climber more often if potted.
Clematis will climb up any structure if there is something for it to attach itself to like a trellis, textured wall, even a shrub or tree. Lunn walks her yard with jute and a pair – or three – of sharp scissors in her pocket, ready to tie up a meandering vine.
Keep an eye out for browning leaves, a sign of a stressed-out clematis. Remove the damaged areas of the vine by pulling it away from the support and trimming it, Lunn said.
To overwinter potted clematis, trim back the vine and lay the pot on its side in a shed or unheated garage so the plant can go dormant. Clematis planted outdoors like to have their roots protected from Iowa winter weather.
Although most clematis are sun-lovers, clematis like their roots to be shaded. Lunn surrounds each root with a 1-foot wire cage and fills it with leaves. The cage also protects the delicate stems from hungry rabbits. Other ideas to shade the roots include placing a large stone in front of the plant’s base, planting a hosta, or covering the area with several inches of mulch.
“You want to mulch them well in the wintertime,” Lunn said.
Clematis Group 1
Group 1 clematis bloom early- to mid-spring. Trimming the blooms after they fade encourages re-blooming. Lunn trims about 6 inches off the end of the vine.
“I can get some of my vines to bloom four times in the summer if I do it right,” Lunn said.
Because this group blooms in the spring on old woody vines, don’t trim the vine extensively in the fall. Instead, prune after bloom in spring because they spend all summer growing to bloom next spring.
Lunn recommends Montana and Alpina varieties for excellent tolerance of Iowa winters. She grows Montana with good luck in part shade – and it gets big.
“When they say 15 feet, they mean 15 feet in each direction,” Lunn said.
Piilu is a shorter vine, growing between 6 and 8 feet. Its first blooms in spring are double, then later blooms are single blooms.
Clematis Group 2
Group 2 clematis start blooming in June or July, and when trimmed after blooming can go as late as September, Lunn said.
The vines are covered with showy masses of large flowers, many in jewel tones, with the red and cranberry colors the hardest to find. Some blooms are as big as 8 inches across, particularly in warmer zones. There’s Little mermaid in a soft peachy pink; it will grow in part shade. Silver Moon will grow in almost full shade but won’t get as big. If you’re looking for a pure white vining plant, try Guernsey Cream: it will bloom two or three times each summer.
Bicolor varieties, available at most area garden centers, are easy to grow, stay to a manageable height and produce big blooms, Lunn said.
The clematis likes to be supported. The vines will run across along the fence line, or you can prune late in fall and grow in one area, Lunn said. But if you let them grow a long length, it’s not likely the lower portion of the length will bloom, she said
Group 2 clematis such as Diamantina also features double blooms that begin as a rounded mound in the center, gradually folding open row after row.
“They’re not hard to grow. They give you a lot of blooms,” Lunn said.
Group 2 clematis grow on old and new wood. The vines should be trimmed in fall to about 12 inches after the leaves die.
Group 3 clematis
Group 3 clematis bloom from July through the fall. There’s a wide variety of vines in this group. Vines range from 5 feet to 20 feet, and flowers can be large or small. Leaves tend to be small, Lunn said.
Sweet Autumn is covered in tiny, elegant white flowers for a couple of weeks in September. Bees and butterflies love the flowers, Lunn said. It’s a good plant for monarchs to feed on as they travel through Iowa on their migration.
She has Nelly Moser pale pink running up through a rose vine. It doesn’t seem to bother the rose as long as you don’t let the clematis get too big.
Because Group 3 clematis tend to bloom on wood that grows during the summer, don’t trim back severely in the fall. But do prune, or the mass will become tangled with bare stems at the base, Lunn said.
Jackmanii, with its deep purple blooms, is a good clematis to start with and was the first clematis Lunn ever grew. It can rise 20 to 25 feet – or higher.
“It’s hardy no matter whether you’re zone 4 to 8. It doesn’t care what kind of winter we have and blooms very well in the summer,” Lunn said.
Her Jackmanii grows in part shade, backed up by a trellis on one side, lilac on the other. She cuts hers all the way to the ground. “It flowers on old or new wood, and if I don’t do that, it will flower about 20 feet out on each end, and it won’t be flowering in the center where I want it to bloom,” Lunn said.