How to Grow and Care for Sweet Autumn Clematis

Sweet autumn clematis is a perennial flowering vine that produces sweetly fragrant flowers in the late summer and early fall. This twining vine has leathery, shiny, dark green leaves with numerous small white flowers. When in bloom, it gives the appearance of fleece.

The vine has a fast growth rate, gaining a few feet in length each year. This might be a welcome trait if you want to cover a fence or an unsightly structure. However, planting sweet autumn clematis is also highly problematic as the vine is considered invasive in most of the eastern United States. Planting sweet autumn clematis is not recommended unless you cut off all the flowers before they go into seed, which is the only way to contain the spread of this non-native vine.

Like all clematis, it is toxic to humans and pets.

Sweet Autumn Clematis Care

Here are the main care requirements for growing sweet autumn clematis:

• For best flowering, select a location in full sun where the soil has good drainage.
• Give the plant about one inch of water per week.
• To support the massive and heavy vine, ensure the plant has a trellis or other structure to climb.
• To hide the sparse bottom of the vine and keep its roots cool, plant groundcovers around the base.
• Start applying a low-nitrogen fertilizer in the spring and repeat every few weeks until mid-summer.
• After flowering and before it sets seed in the late summer or early fall, prune it rigorously to contain the invasive spread of the plant.

Warning

Sweet autumn clematis has been reported invasive in Alabama, Delaware, Florida, Georgia, Illinois, Maryland, New Jersey, North Carolina, South Carolina, Tennessee, and Virginia. Its seeds easily disperse by wind and the vine grows fast and vigorously, forming dense blankets that choke the plants underneath.

Light

Plant sweet autumn clematis in full sun with a solid six to eight hours of sunlight each day for best flowering. However, these vines tolerate a considerable amount of shade—unlike most other clematis species—if you are willing to put up with some reduced flowering.

Soil

The plant is not fussy about soil conditions if 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.

Water

Sweet autumn clematis has average water needs. Roughly one 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 4 to 9. It does not have particular humidity requirements.

Fertilizer

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 feeding every few weeks throughout the growing season.

Pruning

This vine blooms on new wood, so prune sweet autumn clematis after flowering finishes in the late fall. Doing so will remove the seed heads and prevent self-sowing. Some gardeners cut their sweet autumn clematis plants down to within 1 foot from the ground. To cover a large area, such as a large pergola, prune less severely and leave more of the plant in place but make sure to remove all the spent flowers.

Propagating Sweet Autumn Clematis

It is rather rare that a gardener would need to propagate sweet autumn clematis. To share plants, transplant any seedlings that sprout up around a mature plant to a new location. Another way of propagating the vine is from stem cuttings:

• In the spring or early summer, take a 4 to 6-inch-long cutting of new, green growth just below a leaf node.
• Remove any leaves except for the top two.
• Dip the cut end in rooting hormone.
• Fill a 4-inch pot with soilless potting mix and create a small planting hole for the cutting. Place the cutting in the hole, with the leaves above the soil line. Water it lightly.
• Cover the pot with a plastic bag and place it in a location that receives bright, indirect light. Water as needed to keep the soil moist.
• After about four weeks, very gently tug on the cutting to check for resistance from newly formed roots. Once there is evidence that the cutting has rooted, transplant it to a larger pot.
• Continue to grow it in a pot for the following growing season before transplanting it in its permanent location outdoors.

How to Grow Sweet Autumn Clematis From Seed

Although the plant reseeds freely in an unwanted way, starting it from seed (which requires cold stratification) is a less practiced propagation method. Seed germination is slow and erratic and the vines from seeds have fewer, less fragrant flowers than plants grown from cuttings.

Potting and Repotting Sweet Autumn Clematis

Sweet autumn clematis grows well in containers. Choose a large pot, 15 to 18 inches in diameter with large drainage holes. Keep in mind that clematis wants to climb, so installing a trellis or arbor in or near the pot is highly recommended. Use potting soil blended with a general-purpose, slow-release fertilizer. Potted plants need more frequent watering than plants in the landscape, especially during hot summer weather.

As the plant outgrows its pot, replant it to a pot size a few inches larger than the last.

Overwintering

Sweet autumn clematis is quite hardy, to the point of no worries for the home gardener for overwintering; it will bounce back strongly in the spring as soon as the temperatures rise.

Plants grown in containers should remain outdoors during the winter but need winterization to insulate the roots from temperatures below freezing. Either bury the pot in the ground in the fall or plant it inside an insulation silo during the winter.

Common Pests & Plant Diseases

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 also affect the plant, though generally, they are not fatal. Insect pests include aphids, slugs, snails, scale insects, 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.

How to Get Sweet Autumn Clematis to Bloom

Bloom Months

The blooms usually begin in August and continue through October.

How Long Does Sweet Autumn Clematis Bloom?

The flowers last for several weeks and new flowers are being produced constantly during the two-month bloom period.

What Do Sweet Autumn Clematis Flowers Look and Smell Like?

The star-shaped pure whiteflowers measure 1 inch across. They are small compared to other clematis varieties but the vine is covered in flowers. They have asweet scent with hints of sugar, honey, and vanilla.

How to Encourage More Blooms

Planting the vine in full sun and feeding it a low-nitrogen fertilizer is the best way to make sure the vine blooms profusely.

Caring for Sweet Autumn Clematis After It Blooms

For the best profusion of flowers, prune clematis back to about one foot above the ground after one season of growth. In the coming years, prune the plant down to two to three feet above the ground after the flowers have died back.

Deadheading Sweet Autumn Clematis Flowers

Deadheading the flowers of sweet autumn clematis is key—not so much for an extended bloom but to contain the spread of the plant via seeds.

Common Problems with Sweet Autumn Clematis

Though clematis is an easy plant to grow and quite resistant to insects or diseases, watch out for these potential issues:

Spots on Leaves or Wilting Plants

Dark spots on the leaves could be caused by clematis wilt, leaf spot, or root rot, all of which are often caused by overwatering and poor air circulation. Thin the plants to allow better circulation and remove any infected leaves. If that does not help, consider applying a fungicide.

Note that yellow mottling or spotting on the leaves is often a sign of tomato ringspot virus, which can reach your sweet autumn clematis through the travel of nematodes. This diseases requires removing the affected plants.

White Fungal Growth

The white fungal growth on clematis leaves is often powdery mildew, a common aesthetic problem of ornamental plants. Remove heavily affected leaves during the growing season. In the fall, prune the vine back to 1 foot and safely dispose of the entire plant material in the trash to prevent the fungus from reinfecting the plant in the spring.

From: thespruce