A CLEMATIS FOR EVERY GARDEN
There is a clematis for almost every garden setting: there are herbaceous perennials that are ideal for the front of the border; open shrubby perennials that fill the middle ground; climbers of various heights to companion with shrubs and trees; and immense vines that can cover fences, sheds, and gazebos. Although the word clematis usually conjures up the image of a vine with dramatic large flowers, there are many different shapes, sizes and arrangements of flowers within the genus.
With more than 1000 species and cultivars, the Genus Clematis can often seem overwhelming. It is helpful to look at clematis using the horticultural classifications that the International Clematis Registry and Checklist recommends. In this registry from the Royal Horticultural Society of England, clematis are divided into small and large flowered cultivars and further divided into groups. These groups gather together plants of similar origin and care and therefore are helpful to home gardeners.
First, the ever-popular large-flowered cultivars of clematis are divided into two categories: the Early Large-flowered Group and the Late Large-flowered Group. Each of these groups are pruned differently. These are the groups that cause the most anxiety for eager pruners. Pruning is not difficult once you get used to thinking in terms of early and late. Remember that the vines in both groups are generous and there is no
exact method of care and pruning for either. Each gardener should adapt the guidelines to his or her own garden.
Second, the small-flowered cultivars are arranged in many more groups, most reflecting their specific origins. The groups most commonly found are: Armandii Group; Atragene Group; Cirrhosa Group; Flammula Group; Forsteri Group; Heracleifolia Group; Integrifolia Group; Montana Group; Tangutica Group; Texensis Group; Viorna Group; Vitalba Group; and Viticella Group. Some groups are represented in the clematis trade by only a few cultivars.
(We would like to thank the Royal Horticultural Society, Wim Snoeijer and the many gardeners who have contributed their experience in refining the nomenclature of genus
Clematis to make it useful and relevant to home gardeners.)
Early Large-flowered Group:
This group derives mostly from C. patens in its single and double forms. These are spring blooming plants and, as such, bloom on the wood that set the previous year. The general rule of thumb for pruning these plants is to prune them after they bloom in the spring. Some resources recommend dead-heading at that time; some suggest pruning up to a third of the plant back; and others somewhere in between. A few classic books even recommend cutting back stems at varying heights. All of these recommendations work. The vines perform best if they are fed after this pruning. Many of the plants in this section also bloom again in the late summer or early fall. It is important not to prune the vines after this second round of bloom if blooms are desired in the coming spring. (To complicate matters, here in the maritime Pacific Northwest, we have even found that many of the clematis in this group will bloom in the spring even if they are cut back in the late winter. We don't recommend this to most gardeners because it is not consistent through this group and is only true in specific situations.)
Many of these Early Large-flowered clematis have flower colors ranging from white and soft lavender blue to rich purple and blue. These are all excellent and complementary colors for spring gardens. There are pink and rose flowers as well. In addition, many of these clematis have pronounced reddish central bars on their sepals The best-selling
Clematis 'Nelly Moser' is a perfect example of this. The early bloomers often have flowers that are impressively large in size.
Clematis 'Daniel Deronda' is one of the very earliest blooming blues. Its flowers are exceptionally large and generous - a wonderful display to start the season. The reliable
Clematis 'Asao' is covered in its large, dark rose blooms, of great beauty
Clematis 'Guernsey Cream' is true to its name, bearing its creamy white flowers very early in the season.
Most of the semi-double and double flowered clematis also are in this group. The pruning is the same as for the singles. Many of the double flowers are exceptionally weighty, especially after spring rains. A sturdy structure or shrub will keep the flowering stems from breaking. The flowers of
Clematis 'Vyvyan Pennell' are spectacularly large and it would be a shame to lose them in a sudden shower. We grow
Clematis 'Belle of Woking' in a Rhododendron 'Bow Bells' which offers perfect support to the June blooms. This companionship allows for an extended period of color - first the shrub blooms followed by the clematis. Once the clematis is finished blooming, we cut off the top third or so of the vine, feed, and allow the rhododendron to take its place as an evergreen background shrub in a summer border.
Late Large-flowered Group:
This group is made up of two sub-groups: first, the of cultivars from C.
lanuginosa; and second, cultivars from the Jackman Group which is essentially
C. viticella and its cultivars (in the original cross the selection C. 'Atrorubens' was used) crossed with
C. lanuginosa. Crosses between C. viticella and C. patens are also included. The distinguishing characteristic of this group is that the vines produce their flowers on the current year's growth. Because of that fact, these plants may be hard pruned during the winter to promote new growth. These vines bloom in the summer, many extending their bloom into the autumn. The flowers are most commonly single and come in a rich variety of colors ranging from white, pink and red to blue and purple. The flowers are generally not as large as those of the Early Large-flowered Group and are rarely doubled.
This group is ideal for growing in shrubs because the vines can easily be cut back to allow shrubs a period of time to recover from their summer weight. For example, for many years we grew red-purple flowered
Clematis 'Ernest Markham' in a white flowering Buddleia pruning both back at the same time in late winter. In addition, we grow many clematis in this group on trellises that serve as backdrops to our roses. The trellises offer support but also allow the flowers of the clematis to mingle with the roses. We like to keep the clematis leaves off of the roses to promote good air circulation and prevent disease. We grow
Clematis 'Negritanka' on a trellis above an orange-toned rose. There the purple flowers of the clematis are a perfect complement. As another example, we grow
Clematis 'Madame Édouard André' on a large trellis together with the dark leafed
Vitis vinifera 'Purpurea' to give that vine a color boost during the summer before its green leaves turn purple.
Be sure to feed these plants during the spring and any time you cut them back during the growing season. We use a well-balanced organic fertilizer. Many home-growers recommend organic tomato feed.
The Armandii Group includes the most reliable evergreen clematis that are suitable for the climate of the maritime Pacific Northwest.
Clematis armandii 'Snowdrift' is a garden favorite in the Portland area. Because of its immense size, often more than 25 feet in length, it is used to cover fences and hide unsightly views. Late freezes occasionally damage the buds and burn the narrow, glossy leaves, but for the most part this vine creates the type of dense screen that is so desired by contemporary gardeners. When it comes into bloom in late February and early March, it is spectacular and very fragrant.
C. 'Apple Blossom' is a cross that has pink buds and rounded leaves. It is not exceptionally fragrant.
These are evergreen vines and should be cut back judiciously to keep them under control after they have finished blooming in the spring. Because these plants have fine roots, be sure to plant the vine at the level you find it in its pot.
The first clematis we grew in this group were labeled as cultivars of C. alpina and
C. macropetala. C. alpina once was used to denote flowers that were single while
C. macropetala was used for double flowers. Because there are many other species potentially involved in the development of these cultivars, these terms are now best reserved only for the species names.
In general these are woodland plants mainly from colder climates. They have characteristic bell-shaped flowers that are nodding or down-facing. Single flowers have four sepals and a central arrangement of stamens and pistils. Occasionally they have additional staminodes but their sexual parts are clearly visible. Double flowers are commonly described as looking like "ballet-skirts", a phrase that aptly describes the appearance of the clustered staminodes that make up the interior of the flower. The sexual parts are hidden in these
Because these are woody climbers that bloom on the previous year's wood, a light prune after bloom is generally all that is required. This often promotes new growth and repeat blooms. We have found at the nursery that after many years of growth our atragenes become very dense and weighty and we need to cut them back fairly hard to refresh them. We do this after the spring bloom. We have never lost one by doing this. We always cut above a point where we see active growth. For example, we cut
Clematis 'Willy' back hard once every three years. It still rewards us with masses of spring bloom.
A word of caution about planting clematis in this group. Their roots are very fine and fibrous and not fleshy like their large-flowered counterparts. Do not bury these roots deeply. Plant them at the same level you find them in their pots. Improving the drainage of heavy clay soils can help. We find that they like good drainage. We also tend to plant them in part shade situations where they are protected from the hottest sun. These plants do not do well in warm climates.
One of our favorite recent plantings is C. chiisanensis 'Lemon Bells' which we grow in a large Japanese maple. The lovely yellow flowers of the clematis contrast nicely with the hints of red and pink in the June maple leaves. In the autumn, the silvery seedheads glow in the interior of the tree. This combination grows in a woodland setting.
The vines in this group are from the Mediterranean region but do well in the Portland area because our climate more or less mirrors the climate of their home. They are suitable to other areas with mediterranean climates but do not survive in northern gardens. They are treasured here for their winter blooms which begin in October some years and carry on until the spring. The flowers are generally white to creamy green bells. Many selections have maroon freckling in the interior of the flowers. In some selections, the freckling is so dense that the interior appears maroon. Many have a gloss to their foliage.
C. cirrhosa var. balearica has finely cut leaves.
These evergreen climbers bloom on the previous year's growth. Because they can become immense over time, sometimes it is necessary to prune them fairly hard. Do this in the spring as soon as they have finished flowering. This gives them a season to regrow and produce blooming wood for the coming year. The plants in our garden take a rest after the winter but by summer begin to put on new growth. Although they are not needy of food, we like to give them a light spring feeding to promote good new growth. These vines have fine roots and should be buried at the same depth they have in their pots when planting.
We do not recommend these vines for growing in trees and shrubs. Because they are evergreen and very heavy, we like to grow them on fences and trellises. One combination that we have found very satisfying is growing
Clematis 'Wisley Cream' with
Jasminum officinale on a fence. The white flowers of the jasmine open all summer long. They are replaced by the white flowers of the clematis throughout the winter. During especially cold spells, the flowers may not open. As soon as the temperature climbs, they continue their display.
This group includes clematis from the Subgenus Campanella Section
Campanella. Wim Snoeijer in his recent Clematis Cultivar Group Classification suggests that we use the name Campanella Group instead of Connata.
There are many fine clematis in this section which include plants from both Asia and Africa. Some of the most popular species in this section are
C. aethusifolia, C. connata, C. rehderiana and C.
repens. This last species was only recently introduced to the public as a selection from a collection by Dan Hinkley called
Clematis 'Bells of Emei Shan'.
Clematis in this group can be somewhat shrubby or climbing. Their flowers are nodding or hanging bells which can be white, cream, or yellow, sometimes with a red to purple stain. Flowering can be in any season, depending on the species. The roots are fibrous and not fleshy. Plants in this seciton should be planted at the level they are in the pot at time of purchase.
At our nursery we grow Clematis connata on a low wrought-iron fence which it easily climbs and cascades over. The small creamy yellow bells add a dainty contrast to the large, coarsely toothed leaves. Give
Clematis connata lots of room to grow, but plant it were you will be able to enjoy its autumn flowers.
The Flammula Group includes plants that have been hybridized using such species as
C. angustifolia, C. flammula, C. recta and C.
terniflora. The Flammula Group encompasses both shrubby and climbing clematis. All have white flowers in terminal panicles.
An example of a shrubby species is C.
angustifolia which forms a short herbaceous perennial reaching just above knee-high.
is taller, but it also is non-clinging. This species is most often represented by the form
C. recta 'Purpurea' which has purple young growth that greens out with age. There are many selections from this form that have varying heights and leaf-color. The flowers of this species are often fragrant.
Both C. flammula and C. terniflora are climbing and,in their best forms, are also extremely fragrant. (There is a good reason why
is call the Sweet Autumn Clematis.)
Clematis x triternata 'Rubromarginata' is a cross between
C. flammula and C. viticella. It has clusters of flowers with white sepals that are ringed in red violet and are known for their fragrance.
All of these species bloom on the current year's growth and should be cut back at the end of winter to promote new growth.
The Forsteri Group includes crosses that are derived from clematis species from New Zealand and Australia. These species are all evergreen but have varying growth habits.
C. 'Early Sensation' is truly always a sensation at early spring garden shows when it is covered with large white flowers. Because it is evergreen, it should be pruned judiciously to shape it after it is done blooming. It is hardy for the maritime Pacific Northwest but can be badly damaged by heavy cold winds. It is therefore best to grow it in a sheltered site.
The Heracleifolia Group contains plants that have at least one parent that belongs to the Subgenus
Tubulosa which includes C. heracleifolia, C. stans and
C. tubulosa. Plants in this group are mostly shrubby, but sometimes climbing in nature. Interestingly, the bell-shaped or flattened flowers are either hermaphrodite or unisexual with male and female flowers on the same or separate plants.
A cross between C. heracleifolia and C. virginiana produced the well-known
C. 'Mrs. Robert Brydon'. This semi-climber is often used to spill down slopes or over walls where its clusters of small, open, white flowers that are edged with blue continue throughout the summer into the fall. Another cross with a similar usage and equally long bloom period is
This group also contains selections from C. heracleifolia that are more upright and shrubby.
C. heracleifolia 'Cassandra' forms an open shrub with large leaves and tubular, fragrant, gentian-blue flowers throughout the summer. We also grow a dwarf form of
C. heracleifolia which was found on Omeishan in China. This forms a foot tall, small-leaved shrub.
All plants in this group are herbaceous and should be cut back during the winter to promote new growth in the spring. Because the plants in this group have fine roots, bury them the depth that you find them in their pots. Do
not plant them deep.
Plants in this group are generally non-climbing or only semi-climbing. Most are derived from the species
C. integrifolia which is an herbaceous perennial with stems generally growing from one to three feet. This tough species is found from Central Europe across Russia and into West and Central Asia. The stems of
C. integrifolia have single nodding bell-shaped flowers at the terminals and sometimes at the ends of axillary stems. The many selections from the species produce numerous stems and are quite attractive in the mixed border. Some selections from the species, such as the white-flowered
C. 'Hakurei', have a sweet fragrance that is sometimes described as citrus-like.
In addition to selections from this species, the Integrifolia Group also includes crosses between
C. integrifolia and C. viticella (and others). (Plants from these crosses are often placed in the Diversifolia Group but that is not a group that is recognized yet by the Royal Horticulture Society and therefore we still include them here.) These plants are woody although they bloom on the current year's growth. We cut these plants back hard during the winter. The flowers of these crosses are generally much larger than those of the species and they tend to be variable.
C. x durandii has rather large flattened indigo flowers.
C. 'Alionushka' has large rose-colored bell flowers. Both produce long stems that can be tied up on a trellis, conducted through a neighboring shrub or be allowed to ramble through the garden where their flowers will bloom with surprising companions.
We grow plants in this group in full sun and with good drainage. If they are lightly dead-headed from time to time, it is not uncommon to have them in bloom for three months or more. We have found
C. x durandii to be one of the most drought-tolerant clematis in our gardens.
Clematis in this group are among the easiest and most rewarding for gardeners but they are still underused. Because of their heritage, they are extremely cold-hardy. That fact alone should make them welcome in regions with harsh winters. Many also hold up well to heat. In especially cold climates, plant the roots deeper to protect them from heaving and thawing in the winter.
One exception to the "non-climbing" rule in this group is C. 'Rooguchi' which is a cross between
C. integrifolia and C. reticulata. It does climb (if laxly) and its stems are not woody. We include it here because of its ancestry. This vine has countless fleshy plum-colored bells. We have had reports from customers in warm Southern states who have success with this vine. We have also had reports of it growing successfully in Michigan. When the plant is young, it can exhibit powdery-mildew. We cut it back hard if we see this. It will soon grow new clean stems and bloom a little later in the season.
When gardeners want to cover fences, gazebos, sheds and the like, they often turn to this group. These vines are derived from
C. montana, as well as C. spooneri and C. chyrsocoma. All of these are Asiatic species.
Many of the selections in this section are some of the most vigorous and tallest vines in the Genus Clematis. They bloom on the previous year's wood. If you must cut them back to downsize them, do so just after they have completed their spring-to-summer bloom. Although these are basically one-time blooming vines, they produce such a show of flowers that they exceed most gardeners' expectations. Flowers are not solitary but grow in groups on stems coming from flower-axils. Quite a few of the cultivars have a delicious fragrance often described as almond-like.
C. montana var.
rubens 'Pink Perfection' has extra-large flowers that easily perfume an entire late spring garden.
The foliage is attractive and roughly toothed. Many recent cultivars, such as
C. 'Broughton Star', have very dark, almost black, young growth which greens out as it matures.
Some use these vines to create summer shade over decks, porches and patios. Because they lose their leaves, they allow light into these areas in the winter.
A caution about planting these vines: please plant them at the same level they are in their pot. Do not plant them deeply.
We do not recommend most of the vines in this group for smaller gardens or for gardeners in areas colder than USDA Zone 7.
There are many species involved in the cultivars that are included in this group. Those species belong to Section Meclatis which encompasses
C. orientalis, C. serratifolia, C. tangutica and C. tibetana among others. Sometimes this group is called the Orientalis Group.
When gardeners ask for yellow clematis, we know this is the group that they are asking for. Not all the flowers in this section are yellow, however. Many are white or cream colored and a few are orange-yellow or brownish or even almost black. The flowers are nodding bells and vary in size depending on the cultivar.
Many of the vines in this section can get quite tall. One cultivar that is suited to a smaller garden is
C. 'Helios' which has extra-large yellow bells and blooms through the summer into the fall. The sepals open broadly looking almost like the ridge-line of a pagoda roof. The silvery seed-heads are equal to the flowers in beauty. For a large space, we grow
C. 'Bill MacKenzie' which blooms through the summer into the fall. It can reach enormous heights and cover a fence or gazebo.
Vines in this section are woody but bloom on the current year's growth. Some texts recommend cutting back stems at varying heights to preserve some of the vine's height. We have had good luck cutting the entire vine back to a growth point at the end of winter. A light feed can stimulate new growth. It does not take long for the vine to become large again.
The roots of the vines in this section are fine and should not be buried deeply. Plant these vines at the level they are in their pots. If you garden in heavy clay, use some grit to improve the drainage.
This is a small group containing clematis that have been hybridized by crossing
Clematis texensis with a large-flowered parent. (We have not included the species
C. texensis in this group even if it does bear its name. We include
C. texensis in the Viorna Section.)
Interestingly, the flowers in this group more or less suggest the flowers of
C. texensis in that they are basically not flat but are tulip- or bell-shaped. However, for the most part, the flowers in this group are much larger than those of the species. The tulip-shaped flowers are generally held upright. The bells are more nodding.
Plants in this group do best in full sun, especially C. 'Duchess of Albany' which we find does not produce its soft-pink tubular flowers well unless it has sun for the majority of the day. When it is happy, it can become a substantial vine. The modern, and very popular,
C. 'Princess Diana' is exceptionally attractive and easy-to-grow. The mauve-pink sepals with contrasting rich pink central bars make her flowers quite dazzling, a little like op-art.
C. 'Gravetye Beauty' has the gloss and glamour of a tube of "Fire and Ice" lipstick which it resembles in color. It, too, is a fine grower and can get
fairly tall, its red flowers accenting the garden from summer to fall.
Pruning is easy on these plants. Cut them back hard at the end of the winter and give them a feed to encourage new growth. These climbers need trellises or shrubs to support them.
The plants in this group of clematis are derived from one or more clematis in Section Viorna. Some of the species that are included in this Section
Viornae are C. addisonii, C. crispa, C. fusca,
C. inanthina, C. pitcheri, C. reticulata, and C.
texensis. Many of these species are found in the eastern and southern parts of the United States. Some of them are Asian in origin.
This group contains clematis that are woody climbers, subshrubs or herbaceous perennials, in other words, plants that are variable in their growth habits. An example of a woody climber is
C. 'Odoriba' which grows to eight feet or more.
C. 'Sophie' is an herbaceous perennial that stands just below thigh-high and produces small purple-blue bells in early summer.
The flowers of the clematis in this group are variable in size, but are generally bell-shaped with four sepals. The flowers are more or less nodding in habit. A few clematis in this group like
C. 'Odoriba' hold their bells out toward the viewer allowing a good look at the flower interior. Flowers have large bright pink sepals with white central bars. Although the flowers in this group may be smallish, the majority have unusually long bloom periods and are numerous.
C. 'Odoriba', for instance, blooms all summer until the end of October here at Joy Creek Nursery.
C. 'Myofuku' blooms from June to August. Sometimes it produces so many flowers in can look like a sheet of pink bells.
C. 'Haizawa' blooms as it grows. Flowers start while it is a fairly short vine and continue as it reaches up to 10 feet in height, a process that continues into the autumn.
Because all of the plants in the group bloom on the current year's growth, they should all be cut back at the end of winter and then fertilized to promote new growth.
The Vitalba Group is defined as containing cultivars with at least one parent belong in Section
Clematis (which is a specific botanical section different from the general use of the word clematis). This section includes
C. ligusticifolia, C. potaninii, C. vitalba and C.
virginiana. These are generally large vines with clusters of small white flowers.
C. ligusticifolia is most noticeably seen here in the Portland, Oregon area when its silvery seedheads glow in the autumn light high up in trees along the highways leading to the city. The species in this section are often self-seeding.
C. 'Paul Farges' (commonly sold under the trade name SUMMER SNOW) is a cross between
C. potaninii and C. vitalba. It forms an immense vine that can cover fences, sheds, and large trellises. It blooms throughout the summer and is alleged to be sterile.
Because vines in this section bloom on new wood, cut them back at the end of winter. Also, the vines in this section have fine roots and should be planted at the same depth they are in their pots.
Gardeners in many parts of North America have great success with the clematis in this group. Not only are the vines vigorous and free-flowering; they are also easy to care for and do well in full sun (and many in part-shade).
The cultivars in this group are defined as having at least one parent that is mostly derived from
C. viticella.. (Crosses between C. viticella and C. integrifolia are included in the Integrifolia Group.) This is a group of woody climbers that bloom on the current year's growth and bloom in the summer, sometimes into the autumn. Because they bloom on the current year's growth, it is usually best to cut them back at the end of the winter and feed them at that time to encourage new growth. (This is not to say that there is a law which states that you must cut them down every year. There are some gardeners with specific applications that do not cut back these cultivars but allow them to continue to grow taller year after year in order to attain flowering high up in a shrub or tree or on a wall. What happens in this scenario is that the vine continues to grow from the last point of growth and blooms on the new wood growing out of the wood of the previous year. Over time, a vine treated in this fashion can reach great heights but the bloom is always up high. We have seen
C. viticella 'Etoile Violette' blooming at the top of a thirty-foot tree. Most of us, however, like our vines tidy and in scale with our smaller gardens and that is why we cut these vines back.)
Flowers range in color from white to pink, mauve, violet, red, red-purple and purple. The flowers in general range from tightly to broadly bell-shaped, nodding or outward facing. The nodding white flowers of
C. 'Alba Luxurians' are fairly tightly bell-shaped.
Clematis 'Betty Corning'
has pale lavender bell-shaped flowers with sepals that recurve strongly, periwig style. The out-facing, carmine-rose flowers of
C. 'Carmencita' are flatter and have a twist to their sepals.
Most cultivars are single but there are a few doubles. C. 'Purpurea Plena Elegans' is a classic example of a double flowered member of this group. Its densely congested flowers are like small magenta roses. Some cultivars have flowers with pale sepals that are edged in a darker color. For example,
C. 'Minuet' has small flowers with sepals that are white, veined in red and edged in red purple.
The bloom time is usually in the summer. A few of the cultivars have amazingly long blooming periods.
C. 'Polish Spirit' produces flowers non-stop from June to late October here in the Portland area. It is hard to imagine of a tougher, more rewarding vine.
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