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Clematis Care

Clematis, a genus of several hundred species and cultivars numbering in the thousands from the buttercup Ranunculaceae family, grows largely in the temperate Northern Hemisphere. The hybrid cultivars have been popularly cultivated by gardeners, beginning with C. × jackmanii, cultivated since 1862, with more cultivars constantly being produced. These plants were largely cultivated in China and Japan before being introduced to Europe and elsewhere. 

These plants are mostly composed of climbing woody vines/lianas, with a handful of herbaceous perennials. The temperate species are mostly deciduous, but many of the species growing in warmer climates are evergreen. The stems are rather fragile until they are several years old. The size varies between different species – C. Montana, a vigorous grower can reach heights of 20-30 feet but most hybrids with large flowers grow around 8-12 feet tall, with the smaller herbaceous species only reaching 2-5 feet tall.

The hybrid cultivars produce spectacular flowers of white, violet, yellow, purple, blue, pink, red, and even bicolored blooms. The hybrids with big flowers can have blooms reaching 4-10 inches in width and produce 100 or more flowers each season. The fruit is usually an attractive ball-shaped and feathery structure that is frequently used in arrangements of dried flowers.

There are 3 general flower shapes – flowers in clusters, bell-shaped flowers, and open or flat flowers. Many species have fragrant flowers, while most hybrids are usually odorless, the smaller flower species have many different fragrances, from vanilla, hot cocoa, almond, and more. Flowering seasons range from spring to fall, attracting bees, hummingbirds, and butterflies. 

The climbing varieties can grow on walls, fences, trellises, and other structures, even on shrubs and trees, while some are trained to provide ground cover due to their adaptability and outstanding flowers, these plants are some of the most popular plants grown in gardens. Specialist cultivators frequently display plants from their collections in flower shows like the famous Chelsea Flower Show. 

There are several different varieties to choose from based on height, flower shapes, and colors. If you have space in your garden, you can grow a 10-20 feet tall vine on a trellis or fence. If space is limited, many compact varieties can grow in small gardens or pots.

It can take many years for plants to become mature and start flowering, so it would be better to buy healthy, robust plants from garden centers or nurseries that are close to flowering instead of waiting. 

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Sunlight

These plants prefer sunny locations that get about 6 hours of sunlight but their soil must be kept cool. Growing shallow-rooted plants to provide ground cover or a 2-inch mulch layer can help keep the soil cool and moist. While some cultivars will still flower under partial shade, most need to grow under bright sunlight to bloom.

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Water

These plants need watering once or twice weekly, increasing the frequency in hot weather or if the plants are potted. 

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Humidity

They prefer moderate to somewhat high humidity between 50-80%.

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Temperature

These plants grow well in zones 4-9, with temperature ranges between 30–80°F and a minimum of -30°F although most can’t handle cold and frost that well. 

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Soil

They prefer moist and well-drained soil with a neutral to somewhat alkaline pH. As mentioned above, the soil must be kept cool so a thick mulch layer or a ground cover of low-growing plants is necessary. The soil should be damp but not too soggy as this can affect growth and initiate root disease. 

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Repotting

These plants should never be repotted in spring as they don’t like their roots to be disturbed at this time – summer or fall is a better time to repot. Trim down the plant before repotting, particularly if it is a vine. Transplant it to a slightly bigger container of fresh soil and water it well.

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Propagation

The best method for propagating these plants is from softwood cuttings taken in April or May. You can also divide mature and well-established plants, although this can only be done when the plants are mature enough. 

Cutting:

Fill a container with well-draining compost and water it well and add a top layer of sand. Cut off a 4-6-inch portion of a healthy new stem, which isn’t too woody or very soft, cutting just above a leaf node, leaving just a single leaf on the cutting. Insert the cutting into the compost deep enough to stand by itself. Leave the container in someplace warm in indirect sunlight. Rooting might take about five weeks.

Division:

Only divide the plants if they mature and are well-established. First, trim down the stems, leaving around 4 buds on each stem. Dig deep around the roots to get the whole root ball if possible. If the plant is potted, it is much easier to extract it from the container. Divide the plant into segments, each having a stem with roots. Plant the sections in your garden or separate containers and water them well.

Additional Care

Once they’re established and new growth starts, feed the plants once every 2-3 weeks with a fertilizer specifically for roses or flowering plants.

While some varieties grow as bushes, most plants are climbers. They need some sort of support to climb on, like a trellis or fence. If they can’t find any support, they will stop growing. The kind of support depends on the variety of plants – small-growing vines can grow on poles while larger ones need a trellis, arbor, or fence. Growing them on netting also works. The stems don’t attach themselves to their supports and need to be tied to the supports with twine or fishing line. 

Pruning depends on the plant type, from heavy annual pruning to very minimal. This falls into 3 categories:

Vigorous varieties and hybrids that flower early don’t require pruning, other than an occasional trim to remove tangled stems.

Hybrids with large flowers that bloom in early summer can be lightly pruned when they become dormant to maintain their shape.

Hybrids that flower late can be pruned down heavily when they become dormant, leaving just one pair of buds.

Common Problems

Young shoots are frequently attacked by snails and slugs. Use a copper mesh slug barrier to protect the plants from these pests. 

Powdery mildew usually affects the plants when they are stressed. This fungal disease can be avoided with mulching and proper watering. Remove and dispose of damaged foliage and stems and treat the plants with a fungicide.

If you notice a white, smelly, ooze arising from the stems during spring, bacterial slime flux might be the cause. Damaged items are prone to this infection and preventing damage is the best solution. Cut off the stem below this ooze and it may form new shoots in summer.

Wilt normally attacks large-flower varieties and is caused by another bacterial infection resulting in a rapid deterioration in health, along with leaves and stems becoming black and dying. Infected stems and foliage have to be cut away for healthy growth to resume.

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