The Hoosier Gardener: Climbing or trailing, clematis is queen in the garden

There are collectors and then there are collectors. Deborah Hardwick falls into the latter category with 2,000 clematises at the Hardwick Hall Collection, her central Ohio property.

She shared her knowledge at last September’s Plant Trial Day at the Cincinnati Zoo and Botanical Garden. For instance, she disabused me — and I’m certain others — of some myths regarding the care of the plant known as Queen of the Vines.

For one, she told us we could prune or cut back the side shoots of clematis to reduce its size whenever needed. That’s such a relief since zealots want us to know the “pruning group” of clematis because taking nips and tucks. See the International Clematis Society (http://bit.ly/2HsKGqO) for more about these groups and pruning techniques.

Other Hardwick tips:

• Buy two or three of the same clematis variety and plant them together.

• Plant clematis in a hole 18 inches deep and 15 inches wide, with soil that is well drained.

• Snip off spent flowers early in the season, then cut the plant back by half mid-season.

• In fall, cut large plants back again to tidy it for winter and reduce seeds.

• In spring, cut back hard, or to just above a set of fat buds.

• Keep clematis watered during the growing season. She recommends 2 inches a week.

• Don’t use high-nitrogen fertilizers. Use a fertilizer with a slightly higher middle number.

Hardwick has spent 20 years studying, collecting, growing and now hybridizing clematis. She said she searches for varieties that are easy to establish, have strong stems, flowers that are colorful and durable, tolerate hot weather and are hardy to USDA Zone 5.  Here’s her list of the 10 best:

• ‘Alionushka’ (C. integrifolia), a trailer with 3-inch pendulous flowers.

• C. viorna and related hybrids, bell-shaped blooms and native to the southeast U.S.

• ‘Mrs. Harvey’ (C. integrifolia), trails with three to four months of bloom.

• ‘China Surprise’ (C. heraclefolia), large leaves and is a bee magnet.

• ‘Princess Kate’, slow to establish, but non-stop bloomer.

• C. pitcheri and related hybrids, clustered blooms, native in the Midwest.

• ‘Alita’, rebloomer, a Raymond Evison brand.

• ‘Etiole Violette’, non-stop bloomer.

• ‘Margaret Hunt’, compact.

• ‘Sundance’, mound grower.

I know some of these will be hard to find at local garden centers. Of all of them, the only one I’ve ever seen is ‘Etiole Violette’.

The native ones may be downright impossible. For those, consider shopping native plant sales, such as the Indiana Native Plant and Wildflower Society’s plant sale and auction on May 12, or check out NativePlantsUnlimited.com. PlantDelights.com has the Pottawatomie variety of  C. pitcheri.

BrushwoodNursery.com and GardenCrossings.com are mail order retailers that specialize in different types of clematis.

Jo Ellen Meyers Sharp (hoosiergardener.com) is vice president of Garden Writers Association and co-author of “The Indiana Gardener's Guide.” Write to her at P.O. Box 20310, Indianapolis, IN 46220-0310, or e-mail thehoosiergardener@gmail.com

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