Sweet autumn clematis (Clematis terniflora) is a perennial flowering vine that produces 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, though 15 feet is a more typical mature size. It has a fast growth rate, gaining a few feet in length each year. 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 fleece. The spent flowers are replaced by fuzzy seed heads that are also attractive.
Seeds are best started in the late fall to early winter, and seedlings can be moved outside once nighttime temperatures remain above freezing. However, sweet autumn clematis should be planted with caution, as it is a very vigorous vine that can choke out nearby plants. Plus, it self-seeds readily and can easily spread beyond its garden site. 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||Average, medium moisture, well-draining|
|Soil pH||6 to 7 (slightly acidic to neutral)|
|Flower Color||Creamy white|
|Bloom Time||August to September|
|Hardiness Zones||5 to 9|
|Toxicity||Toxic to humans and animals|
Sweet Autumn Clematis Care
Although it can be used as a ground cover, sweet autumn clematis is more commonly found draped over stone walls or scaling structures such as arbors. It needs a sturdy structure, as the plant can get quite massive and heavy. However, it can be sparse and leggy near the base, so it is ideal to surround the lower area with other plants that hide the bottom of the sweet autumn clematis and keep its roots cool.
Regular feeding and watering will reward you with a large vine blanketed with white flowers by early fall. After flowering is complete, the vine should be rigorously pruned. This will limit the self-seeding that can lead to the invasive spread of the plant.
Plant sweet autumn clematis in full sun for best flowering. However, these vines can tolerate a considerable amount shade—unlike most other clematis species—as long as you are willing to put up with some reduced flowering.
The plant is not fussy about soil conditions as long as there is good drainage. The ideal soil will have a slightly acidic to neutral soil pH, but even slightly alkaline soils generally support the plant quite well.
Sweet autumn clematis has average water needs. Roughly 1 inch of water per week, through rainfall or irrigation, is generally 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 from USDA growing zones 5 to 9. It does not have particular humidity requirements.
Like all clematis species, this plant is a heavy feeder. Apply a low-nitrogen fertilizer, such as 5-10-10, in the spring. Then, repeat every few weeks throughout the growing season.
Is Sweet Autumn Clematis Toxic?
Sweet autumn clematis leaves and sap are toxic to both humans and animals. Toxicity from ingestion is most common, though eating a fatal dose is rare due to the plant’s bitterness and ability to cause mouth irritation. It also can cause irritation from skin contact, though not everyone experiences this.
Symptoms of Poisoning
Symptoms of toxicity are similar in people and animals. They include vomiting, excess salivation, diarrhea, mouth ulcers, dizziness, fainting, and convulsions. Skin contact can result in redness and a burning sensation.
Prune sweet autumn clematis after flowering finishes in the late fall. This will remove the seed heads and prevent them from growing unwanted plants. Most gardeners cut their sweet autumn clematis plants down to within a foot or so from the ground. But if you're trying to get your vines to cover a large area, such as a big pergola, you can prune less severely and leave more of the plant in place.
Propagating Sweet Autumn Clematis
It is rather rare that a gardener would need to propagate sweet autumn clematis. But if you want to share plants, the seedlings that sprout up around a mature plant can be transplanted wherever you wish. Stem cuttings can also be easily rooted. Simply cut a 4- to 6-inch stem segment, plant it in ordinary potting soil, and keep the soil moist until roots develop. This can take six to eight weeks.
As with other clematis species, sweet autumn clematis is prone to clematis wilt, a potentially fatal fungal disease. Foliage might appear dry, withered, and even black on affected plants. Prune out and destroy affected foliage. As long as the disease hasn't spread throughout the entire plant, it will usually bounce back the next growing season.
Powdery mildew, leaf spots, rust, and viruses can also affect the plant, though generally, they are not fatal. Insect pests include aphids, slugs, snails, scale, earwigs, and spider mites. With these issues, look out for discolored foliage, small bugs on the foliage, and the plant generally failing to thrive. Use the appropriate fungicide or insecticide for the problem.