Sweet autumn clematis (Clematis terniflora) is a perennial flowering vine that produces its sweetly fragrant flowers in the late summer and early fall, well after most other clematis plants are finished blooming. Formerly categorized as Clematis paniculata), sweet autumn clematis can grow to 30 feet, although 15 feet is a more typical mature size.
This twining vine has leathery, shiny dark-green leaves. The flowers are small, white, numerous, and fragrant. When covering wood fences or similar structures, a sweet autumn clematis in bloom gives the appearance of a great fleece. The spent flowers are replaced by fuzzy seed heads that are also attractive.
Sweet autumn clematis should be used with some caution, as it is a very vigorous vine that can choke out other plants, and it self-seeds so readily that it can easily escape a garden and naturalize in surrounding areas. It is considered invasive in many areas of the eastern U.S.
|Botanical Name||Clematis terniflora.|
|Common Name||Sweet autumn clematis|
|Plant Type||Perennial flowering vine|
|Mature Size||15 to 30 feet long|
|Sun Exposure||Full sun to part shade|
|Soil Type||Medium moisture, well-drained soil|
|Soil pH||6.0 to 7.0 (slightly acidic to neutral)|
|Flower Color||Creamy white|
|Bloom Time||August to September|
|Hardiness Zones||4 to 9|
How to Grow Sweet Autumn Clematis
This plant prefers to be planted a full-sun location in medium-moisture, well-drained soil, but it has better tolerance for shady conditions than most clematis varieties. It will need a sturdy trellis or other structure, as the plant can get quite massive and heavy. The plant can be sparse and leggy near the base, so it is best to surround the lower area with other plants that hide the bottom of the plant and keep the roots cool.
Regular feeding and watering will reward you with a large vine blanketed with white flowers by late summer and early fall. After flowering is complete, the vine should be rigorously pruned down to ground level. This will limit the self-seeding that can lead to rampant, invasive spread of the plant.
Plant these vines in full sun for best flowering. But these vines will tolerate a considerable amount shade, as long as you are willing to put up with reduced flowering.
Well-drained, medium moisture soil is ideal for sweet autumn clematis, but the plant is not at all fussy about soil conditions, provided it doesn't sit in wet soil. The ideal soil will have a slightly acidic to neutral pH, but even slightly alkaline soils generally support the plant quite well.
Sweet autumn clematis has average water needs—1 inch per week, through rainfall or irrigation is sufficient. Withhold additional water during rainy spells, as this plant doesn't like to sit in wet soil.
Temperature and Humidity
Sweet autumn clematis grows vigorously in the climate conditions across its entire hardiness range, USDA zones 4 to 9.
Like all clematis, this is a heavy feeder. Apply a low-nitrogen fertilizer, such as 5-10-10 in spring, then every few weeks through the growing season.
Propagating Sweet Autumn Clematis
It is rather rare that a gardener needs to propagate sweet autumn clematis, but if you want to share plants, the volunteer seedlings that sprout up around the mother plant can be transplanted wherever you wish. Stem cuttings can also be easily rooted by cutting a 4- to 6-inch stem segment, planting it in ordinary potting soil, and keeping it moist until a root system develops. This can take 6 to 8 weeks.
Pruning Sweet Autumn Clematis
This vine blooms on the current year's growth. Prune it hard after flowering is complete in the late fall. Pruning in fall rather than early spring will remove the seed heads that can cause the plant to spread invasively. Most people cut the plant down to within a foot or so from the ground. But if you wished to give your vines a "head start"—to cover a large pergola, for instance—you can prune less severely (that is, leave more of the old vine in place).
Comparison With Other Flowering Climbers
Because sweet autumn clematis vines can be invasive plants, you may want to consider alternatives.
Virgin's bower (C. virginiana) is a native alternative for Eastern North America. If you do not mind switching from numerous, small, white flowers to fewer, but larger ones that are pink or purple, simply grow any of the popular non-invasive clematis varieties, such as Jackmanii, Doctor Ruppel, and The President. These three alternatives, however, are shorter vines, so do not expect them to cover large eyesores as fully as sweet autumn clematis does.
If it is a white-flowered clematis that you are after, you have several options other than autumn clematis and virgin's bower. Although the fragrance will not be as pleasing, some good non-invasive alternatives include:
- Clematis armandii: This evergreen clematis grows 10 to 12 feet tall and is suitable for zones 6 to 9.
- C. recta 'purpurea': This fragrant 4- to 8-foot plant is a non-climber suitable to zones 3 to 9. The cultivar name comes from the purple color of the new leaves.
- C. 'Henry': This clematis hybrid is 10 to 12 feet tall and is well suited for zones 4 to 9. The flowers are particularly large.
- C. 'Fragrant Star': This is another large-flowered hybrid. This fragrant plant grows 6 to 8 feet tall and is suitable for zones 4 to 9.
- C. flammula: This fragrant variety grows 10 to 15 feet tall and is suitable for growing in zones 4 to 9.
Common Pests and Diseases
As with other clematis species, C. ternifola can be affected by clematis wilt, a potentially fatal fungal disease. Prune out and destroy affected branches. Even if the plant appears to be devastated, it will usually return the following spring.
Powdery mildew, leaf spots, rust, and viruses an also affect the plant, though generally, they are not fatal. Insect pests include aphids, slugs and snails, scale, earwigs, and spider mites. Insecticidal soaps and oils are better options than chemical controls to address insect pests.
The most common problem with sweet autumn clematis is controlling its rampant spread. This self-seeding vine requires considerable yearly effort to pull out volunteer seedlings that sprout up wherever you don't want them—such as in the middle of a hedge. Any number of gardeners have found themselves destroying sweet autumn clematis vines entirely after a year or two of being enchanted by the flowers and fragrance. If you choose to grow it, make sure to plant sweet autumn clematis in an area where it will be easy to supervise.
Bloom time for sweet autumn clematis is late summer to early fall when many other perennials are done blooming for the year. This makes C. terniflora a popular choice for the four-season landscape, in spite of its invasive nature. Although it can be used as a ground cover, the plant is more commonly found draped over stone walls or scaling structures such as arbors. A well-situated arbor smothered with a blooming sweet autumn clematis vine in fall can certainly serve as a focal point in the landscape. The vine's white flowers also make it effective in moon gardens.