Looking for a plant loaded with colorful blooms that could climb a wall or clamber through a shrub? Clematis is the answer.
Clematis are endlessly fascinating (and potentially confusing) because of the many choices of a seemingly endless variety of species and cultivars. They are placed loosely into groups according to their bloom time and pruning needs. The type will be indicated on the plant tag.
If you do not know which type you have and, therefore, are unsure about when and how to prune, flowering time can be your guide.
Growing by group
Spring-flowering types (Group 1 or A) bloom on old wood, which are the stems formed the year before. These are wide reaching, 12 to 30 feet. Prune lightly after flowering to shape and restrict them. If pruned later than June, they may not bloom the next year.
Clematis montana is in this group. Trail it along the top of a fence for a spectacular April show. Cultivars bloom pink or white.
Clematis armandii, an evergreen clematis, blooms early in the spring with white, scented flowers. Thin out after bloom so it does not become a tangle of old stems.
Large-flowered, summer-blooming clematis (Group 2 or B) may be the ones we think of first when we think clematis. The blooms are up to 6 inches across and range from red to pink to white to blue or purple.
In this category, I have always admired ‘Ramona,’ with lavender-blue flowers from June to September. Large-flowered hybrids grow to 8 to 12 feet. They bloom both on last year’s wood in May and June and again on new growth later in the summer.
Prune them in February, before new growth starts, balancing the plant with longer and shorter stems so flower bloom is spaced over the entire plant. After the first bloom, thin out older stems to encourage new growth.
Renovate an untidy plant by cutting it to 18 inches before growth starts in the spring. You lose the early blooms but not the late-season ones.
Summer and fall flowering clematis bloom on new wood only (Group 3 or C). Because they bloom on the current-year growth, they are cut down each year to two sets of buds on each stem as close to the ground as possible.
Mature plants will put on 8 to 12 feet of growth in a season.
Viticella clematis (Clematis viticella) and its varieties are in this group. They are very useful when you want a climber that is easy to manage because the pruning is simple.
Not all clematises are climbers. Herbaceous clematis behave more like a perennial plant, dying to the ground each year.
In my garden, I let Clematis recta grow up into a tomato cage to keep it from flopping over and am rewarded by profuse clusters of small, white flowers in midsummer.
The variety purpurea has bronze-purple new growth. Clematis heracleifolia has large leaves and grows to a 3-foot clump that needs no support. The lavender-blue hyacinth-like flowers are fragrant.
Other ways to display
When you have no more room in the garden or want to ornament a deck or patio, grow clematis in a container. Select a pot at least 18 inches in every dimension and fill it with potting soil amended with coarse peat moss so that it will both hold moisture and be fast-draining.
Most of the large-flowered hybrids will do well in pots, as will the viticella group. Provide a trellis in the pot or on the wall for the plant to grow on.
Combine clematis with climbing roses on trellises or arbors for dramatic effects. You may want to choose clematis types that bloom before or after the roses to extend the season of color, or coordinate your selection so both rose and clematis are blooming at the same time. The peach tones of the climbing rose ‘Compassion’ are a good foil for the magenta-purple clematis ‘Ernest Markham.’
A good book on the topic is “The Rose and the Clematis as Good Companions,” by John Howells, published by Garden Art Press in 1996.
Clematis can be grown into trees and shrubs. Try Clematis montana in a Western red cedar, or use the golden leaves of Robinia pseudoacacia ‘Frisia’ to host the dark-purple flowers of Clematis ‘Etoile Violette.’
Encourage Clematis ‘Comtesse de Bouchard to scramble into Ceanothus ‘Julia Phelps.’ The dark-evergreen leaves and blue flowers of the ceanothus will make a good foil for the mauve-pink clematis.
With the wide variety available, you have no excuse to find at least one spot in your garden to add the stunning color that clematis bring to your garden.
PHIL WOOD is the owner of Phil Wood Garden Design in Seattle.