Five fascinating facts about clematis

May 17, 2019

Clematis is a genus of mostly vining plants, with colorful, showy blooms. Flowers come in a wide variety of forms from bell or cup shaped to large, open stars. There are dozens of types and varieties, from compact, shrubby vines at 3- to 4-feet to long ramblers at 12- to 15-feet. Clematis are surprisingly cold hardy, with most varieties hardy to -30 or colder with proper winter protection. The plants can survive and provide summer bloom color for about 25 years, except the first few years during establishment. Most guides recommend that any flowers the first two years be removed to provide maximum energy to the vine and its root system. Read on for more insight into this quirky, long-time gardening favorite.

Head in the sun, feet in the shade. This saying provides guidance for the best planting scenario for clematis. The vines like fun sun, but cool, moist soil. This is possible in many locations around the house, especially where the root zone might be shaded by other plants, a fence, or structure. Clematis tolerates some light shade, but prefers full sun. At Mountain Valley Gardens in Klamath Falls, Jackmanii “Superba” clematis are planted on trellises at the ends of several plant benches. The plant benches create the perfect “shaded feet” that clematis love, keeping soil cool around the roots.

Bare root vs. potted. Bare root plants, often available in boxes, are typically stressed during storage, and can be far more difficult to transplant successfully. Mountain Valley staff report they sell only containerized clematis due to a high failure rate on bare root plants. Bare root starts can be planted earlier than potted plants. Decayed or dead roots should be trimmed off before planting, and the plant watered in immediately. It usually takes three years for a bare root clematis to have much bloom. A potted plant will cost significantly more due to greater production and overhead costs, but has a greater chance for transplant success. Potted plants should be transplanted to the garden after danger of frost, or protected during cool nights, and may bloom well the second year.

High performance, high maintenance. Clematis are not for the “hands-off” gardener: they need regular maintenance to succeed. Roots systems may be as much as 2-feet deep, so deep and regular watering is essential. Regular fertilizing will prolong bloom period and increase number of blooms. Pinching back a few of the vines helps spread the flowers all over the plant rather than just at the ends. The vines must be pruned, with timing depending on type. Winter protection is necessary, and also varies with the type of clematis. Some gardeners deadhead clematis to encourage even more bloom, while others enjoy the look of mature seed heads on the plant.

Training required. Most clematis are rambling vines, and need a support system, whether a trellis, fence, or old rusty tractor. Weaving or wrapping the vines around the support to get them started is suggested. There are clematis that bloom on old wood, on old and new wood, and those that bloom only on new wood. For best results, trellising and pruning tailored to the bloom location is beneficial. Leaf petioles (non- botanists would call them leaf “stems”) must be able to wrap around something for the vine to grow.

Character building. Mostly insect and disease free, clematis are old-time garden staples that drift in and out of popularity with the decades. Clematis are large, bold plants that can add character to the garden for a long time. There are hundreds of cultivars (cultivated varieties) in different colors, shapes, fragrances, and vine vigor — one for any garden personality. Clematis are likely best suited for less formal or naturalized gardens where their rambling shapes are best appreciated. Some are very fragrant.

Locally, staff at Mountain Valley Gardens agreed that the Jackmanii group were among the best performers in our area. Jackman’s clematis are among the easiest to grow and most cold hardy. Many of the newer types of clematis are derived from the Jackmanii group. They are profuse bloomers in whites, reds and violets. Another favorite was clematis tibetiana ssp. tangutica, known to non-plant nerds as Golden Chinese clematis. This yellow clematis has seed heads that persist on the plant and are sometimes used in floral arrangements. Two employees noted having had challenges with “Nelly Moser,” a striking mauve and pink clematis that blooms on new wood. For detailed information on the types of clematis that perform well in cold areas, including size, bloom color, bloom on old or new wood, and much more, University of Montana’s “Growing Perennials in Cold Climates” (Mike Heger, Debbie Lonnee and John Whitman) is indispensable. The book is carried at Klamath County libraries.

Nicole Sanchez is horticulture faculty at OSU’s Klamath Basin Research and Extension Center. For more information on this or other gardening topics, contact Nicole at Nicole.sanchez@oregonstate.edu or 541-883-7131.