Clematis Introduction

Clematis is a Greek word which simply means a climbing plant. It is usually pronounced clem-AT-is, or CLEM-uh-tis, the first being the North American pronunciation and the latter European. There are several hundred clematis species world-wide and thus flowers are produced in almost any colour. Clematis come from the botanical family Ranunculaceae. Flowers in the Ranunculaceae family are typically radially symmetrical and have sepals rather than petals. Typically, sepals sit behind the petals and only serve to protect a developing bud. Clematis instead have elongated, showy, sepals adapted to attract pollinators.

Clematis plants are known for being hardy with the exception of some species, particularly evergreens, which can only take a few degrees of frost. The vast majority of clematis are climbers. Two notable exceptions are the herbaceous species C. heracleifolia and C. integrifolia, which fit well in a perennial garden border. If not given room to climb many cultivars will ramble through shrubs or even make an effective ground cover.

Clematis are the aristocrat of climbers; their rich hues and varied bloom times enable the gardener to have masses of blooms from late winter to late fall. To accomplish this, varieties with different bloom times can be grown together or planted in complimentary areas of the garden. Clematis can be chosen to enrich any garden, no matter how large or small. Some of the species, if left to wander, will easily grow 30’ (9m), while others mature at 4-6’ (2m). The hybrids are on the whole more compact with the majority maturing at the 8-12’ (2.5-3.5m) range. Cultivars that have the potential to grow tall can also adapt to smaller spaces.

Most clematis varieties produce single flowers. These range in size from as small as 1” (2.5 cm) to as large as 10” (25 cm) across. Some varieties produce double flowers, others produce both single and double flowers. Most double flowering varieties will bloom double on the previous season’s growth, early in spring, and then produce single blooms in late summer or early fall on the current season’s growth. If pruned improperly, these varieties will produce single blooms only.

Clematis in North America

The blooms of the clematis often change color, some very markedly through the life of each flower, particularly when grown in the full sun. Pastel colors will hold their colour best if grown in some shade. After the flowers are finished, the very attractive seed heads stay on the plant and can make a welcome addition to most flower arrangements. If left on the plant they sometimes remain well into winter.

Many of the clematis species are scented, although none are strongly perfumed. Even though the scent of a single bloom is not powerful, the mass of blooms produced can fill the air with fragrance. The most highly scented is the tender species C. armandii. Of the large flowering hybrids, only a handful of varieties such as Fair Rosamund, Vancouver Fragrant Star, and Capitaine Thuilleaux produce any noticeable scent. Under the variety descriptions that follow, those with fragrance have been noted.

Clematis have some specific climate related requirements. Clematis grow and bloom much better if they have a dormant period of approximately six weeks. Night temperatures of about 45°F (7.5°C) or colder for a week or more is enough to put them into dormancy.

Gardeners should be aware that most of the excellent books on clematis originate in England, where climatic conditions are quite different from those in most of North America. For this reason, some of the notes in this publication will differ from the English recommendations. The notes that follow provide a North American perspective to gardening with clematis.

In temperate regions where temperatures never drop below 0°F (-20°C), clematis plantings are limited only by imagination. Picture clematis cascading over a fence; enjoy a vine covered cottage; delight in its rambling through your trees. Clematis make a great companion plant. A summer blooming clematis roaming through a climbing rose is a favourite choice.

Clematis are not a heavy strangling vine and will grow through their host doing very little damage. Most varieties perform well in full or filtered sun. Although in general clematis prefer four or more hours of good light each day, some varieties will grow well in lower light, including a bright north wall.

The Cultivation of Clematis

In colder climates, where winter temperatures often drop below 0°F (-20°C), foundation planting and mulch will help to ensure a long life. Full sunlight and long days are ideal growing conditions for clematis.

Within the group A’s the alpinas and macropetelas are very cold tolerant. Group A clematis rely on the previous year’s growth for next year’s flowers, and often produce a bark to protect against the winter’s frost.

Group B clematis will often freeze to the ground in colder areas. When this occurs, a proper planting depth will ensure that new growth will come from dormant buds under the soil. Flowering will take place a few weeks later than it would have in a temperate region. For example, large flowering group B’s such as Nelly Moser will bloom well but a bit later. Some double flowered varieties such as Blue Light, bloom double on new and old growth, while most doubles such as Vyvian Pennell only bloom double on the previous season’s growth. These bloom single on the current season’s growth. Thus, if the previous season’s growth was frozen to the ground, only single flowers would be displayed. For this reason double flowered varieties are not always best suited for colder regions.

Single flowered varieties, particularly the group C’s, are most popular in these climates. Jackmanii Superba, the viticellas and many other varieties will bloom similar whether in cold or temperate climates.

In hot, dry, summer climates, it is imperative that clematis have shelter from a baking sun. If planting on a sunny south or west wall, clematis need to be protected from the reflective heat of the sun. Under these conditions, the old adage of; “their heads in the sun and their feet in the shade” must be adhered to at all times. An excellent method of accomplishing this is to plant behind a low growing shrub that will shade the first 3’ (1m) of the plant.

What pruning group is my clematis?

Perhaps you want to prune your clematis but you don’t know what variety you have. This section can help you narrow your plant down to a pruning group.

When does it flower?

The easiest way to tell what pruning group your clematis belongs too is to observe its flowering time. If it’s in early to mid-spring it’s a group A for sure. Group A’s typically only have one flowering period that occurs in April-June. All other groups have longer blooming periods that begin late spring or early summer. Group B1’s flower in May and June, and then once again in September. B2’s flower similar to group B1 when grown in part shade. In full sun, B2’s will have more flowers on the softer new growth that bud throughout summer. Group C’s usually flower continuously from June to September.

What do flowers look like?

All clematis with large blooms are either group B or C. All group A clematis have small flowers, however, not all clematis with small flowers are group A’s. Group C’s can have large or small blooms, while group B’s are all large. Group C’s typically have between 4-6 sepals while group B flowers always have at least 6 or 7. A ‘double’ is a flower with multiple layers of sepals. If it is a double that is 10 cm wide or larger then it belongs to group B.

What do the leaves look like?

Are the margins smooth or serrated? In other words, do the edges of the leaves have little teeth like a sawblade? If so, it is probably a group A. Two exceptions are rhederiana and the heracleifolias which do have serrated leaves but belongs to group C. Another exception is the evergreen C. armandii which has smooth leaves but is pruning group A. All alpinas, cirrhosas, macropetelas and montanas are in group A’s, and all have serrated margins. Different subgenera often have specific characteristics. For example, texensis have rounder shaped leaves, while tangutica have smaller, slender, pointy leaves. Both of which are group C. Most clematis have three or more leaflets, whereas, integrifolias often have only single leaflets and are also group C’s.

Climbing Plants and the Future

Incorporating plants into your life is very important for both the health of yourself and the environment. Plants increase oxygen levels in the air you breathe and purify air by removing toxic, volatile, organic compounds (VOCs), such as formaldehyde and benzene. Plants trap these toxic compounds and move them to the soil where microorganisms convert them into food. Research also shows that adding greenery to your life can greatly benefit your physical and mental health.

One of the easiest and most effective ways to add more greenery to our cities is to cover the vast, unused space on the sides of buildings. In a world that is becoming increasingly urbanized; vertical gardening has become a popular theme in sustainability. However, typical vertical gardening has several limitations due to the weight of the soil and plant material that must be incorporated in the building design; becoming costly over time. Climbing plants such as clematis overcome these challenges by only requiring a climbing surface, a relatively small amount of soil and minimal care.

Clematis are well adapted for covering vast areas by utilizing their slender, light-weight frame without damaging the structures or buildings they are climbing on. Climbing plants use a special technique called circumnutation, which allows them to effectively search out their surroundings. By swinging their growing tips in large circles, clematis search an area before choosing to attach itself to one spot over another. Clematis are also well adapted to support pollinator populations. Clematis are very attractive to pollinators because of their showy colours, their abundance of flowers, and copious amounts of pollen and nectar. Hopefully, citizens and city planners will continue to learn more about clematis and other climbing plants, so we can continue to better utilize their unique potential.

All plants produced by Clearview are grown using biological controls such as beneficial insects, bacteria and fungi, and without the use of pesticides that are particularly toxic to pollinators such as neonicotinoids or organophosphates. We continue to search and select for the best genetics and varieties