How to choose and grow clematis
Of the more than 200 clematis species, most are deciduous vines; exceptions include useful evergreen vine Clematis armandii, as well as some interesting upright herbaceous types.
Attractive blooms come in a wide variety of shapes; they may resemble bells, stars, tulips, saucers, urns—even miniature lanterns. Each flower consists of a central brush of stamens surrounded by petallike segments called sepals. Range of flower colors is wide, from pastel pinks to crimson red; periwinkle blue through soft lavender shades, rich magenta, and dark purple; and pure white through creamy tones and even golden yellow. Unless otherwise specified, blooms are 4–6 in. across. Float cut flowers in a bowl of water to make a choice indoor display. Burn cut ends of stems with a match to make flowers last longer. The blossoms of the large-flowered hybrids and a few species are followed by fluffy clusters of seed heads, also useful for flower arrangements.
Leaves vary from pale to dark green, usually divided into leaflets. Leafstalks twist and curl to hold plant to its support.How to choose and grow clematis
Choosing a site. When deciding where to plant your clematis, remember that most types need 5–6 hours of sunlight to produce the greatest number of blooms. Site vining types next to an obelisk, trellis, fence, or arbor to give stems support for twining; or plant near the base of a shallow-rooted shrub or tree and let the vine scramble up into it. You can disregard the advice to plant clematis “with their feet in the shade and their head in the sun”—provided your plants are kept properly mulched and watered. To reduce competition for nutrients and moisture, make sure any closely neighboring plants are not too vigorous; shallow-rooted annuals and delicate groundcovers are good choices.
Planting. Dig a large hole, up to 2 ft. wide and deep, and plant in rich, loose, fast-draining soil; add generous quantities of organic matter. Add lime only if soil tests indicate a calcium deficiency. For large-flowered hybrids, as well as species such as C. crispa, C. integrifolia, C. pitcheri, C. terniflora, C. texensis, and C. viticella, plant with the crown (the point where the stems emerge from the soil in the nursery container) 3–5 in. below ground level. Deep planting ensures disease- or cold-damaged plants will resprout. Others can be planted with their crowns at ground level. Stems are easily broken, so plant carefully and protect with wire netting if near a path or where pets or children might brush by and snap them off at the base. Apply a 2–3-in.-thick layer of mulch around (but not touching) the stems to keep the roots cool.
In desert areas plant where there is protection from afternoon sun and strong winds. If you’re planting a deciduous clematis, cut stems back to 6–12 in. from the ground or to two or three pairs of growth buds, whichever is lower. Late in the following dormant season, cut the plant back to two or three pairs of buds; train shoots emerging that second spring. Don’t prune evergreen vines at first; just start training shoots onto their support.
Plant care. Clematis need regular watering and a steady supply of nutrients. Don’t let them dry out, and apply a complete liquid fertilizer monthly during the growing season.
Pruning. The basic objective of pruning mature clematis vines is to get the greatest display of flowers on the shapeliest plant. Pruning is not complicated, and these are forgiving plants that will soon recover from any mistakes. The type of pruning you do depends on when your plants flower. If you don’t know which kind you have, watch them for a year to see when they bloom, then proceed accordingly. Do keep in mind that dormant stems of clematis can look dead. Spring-blooming clematis (which may actually bloom in late fall or winter in mild-winter areas) bloom on stems produced the previous year. After bloom has finished, thin out weak or tangled stems, remove any dead or damaged growth, and cut stems back to the first (topmost) pair of healthy leaf buds.
Summer- and fall-blooming clematis bloom at the ends of new stems that were produced in spring of the same year. These vines should be pruned when their leaf buds emerge—this can be any time from late fall to early spring depending on whether you live in a mild- or cold-winter climate. Cut all the stems back to 12–18 in. above ground level, making each cut just above a pair of healthy leaf buds.
Twice-flowering clematis bloom on the previous year’s stems in spring, then again on the current year’s shoots in summer and fall. In late fall or early spring, prune lightly to thin out excess shoots or untangle stems. After the early blooms fade, prune more heavily so that new shoots will develop for the second round of flowers.
Pests and diseases. Aphids, mealybugs, scale, and whiteflies occasionally affect clematis. Snails, slugs, and earwigs may require control. Powdery mildew can be a problem on some types. Stem rot is a potentially serious disease of clematis. This fungal infection causes browning and wilting of leaves along an entire stem (it is sometimes referred to as “wilt”). Infection begins at the base of the stem, near the soil line. Small stems are more likely to become infected, so buy the biggest plant possible, and try not to break new shoots when planting. To treat infected plants, cut off all diseased parts, then disinfect your shears with diluted household bleach or another broad-range disinfectant. Dispose of diseased stems in a sealed plastic bag to avoid spreading fungal spores. Infected plants will produce healthy new shoots.
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