Last Updated on October 31, 2021 by Phil
The sweet autumn clematis refers to a couple of different varieties of the Ranunculaceae family. As such, it can be confusing. In this article, I’ll cover the Clematis terniflora, which is also commonly known as the Japanese Clematis and virgin’s bower in addition to sweet autumn clematis.
The first name is uses to separate it from C. terniflora (the other sweet autumn clematis) which hails from New Zealand.
That said, the Clematis terniflora is actually native to a few other Asian countries including China, Korea Taiwan and Mongolia. You’ll also see it in Russian Siberia.
However, the plant has since been naturalized here in the United States. And, you’ll see it the East and Midwest including regions of Florida, Georgia, Alabama and South Carolina.
The plant is a fast growing flowering vine that’s know for its fragrant and beautiful blooms. Its ability to climb up garden structures also makes stand out, with the ability to get up to 30 feet high.
Sweet Autumn Clematis are a great addition if you want to add elegant white flowers the bloom in the fall. These feature a star or cross shape measuring between 1 to 3 inches big and 4 to 5 petals.
In addition to their climbing ability, they can work as ground cover as well. However, they’re best displayed on vertical spaces like trellises arbors, walls, fences and pergolas.
Sweet Autumn Clematis Plant Care
Sweet Autumn Clematis Light
Like other clematis, the sweet autumn clematis grows best in full sun. you’ll want to give it at least 6 hours of sunlight daily if you want to see it blossom the best.
That said, it can tolerate partial shade much better than other clematis varieties. So, you can keep it somewhere with a bit of a shade. But, be aware that it will flower less in this condition.
As such, it is up to you to balance things out between the amount of sunlight and its blooming ability. It is likewise worth noting that the plant likely won’t bloom until the second year.
Because of the plant’s size, it isn’t a good option to keep indoors. That said, you can do so until it gets to about 5 to 6 feet before transplanting it outdoors. Also, many gardeners start it from seed indoors before moving it outside.
Another option is to grow it in a container. This is a good option if the soil in your garden is poor or heavy. Similarly, growing clematis terniflora in containers allows you to move it indoors in the winter if you live outside the plant’s hardiness zones.
The biggest advantage of pots is you can easily move it to where it receives the perfect amount of light. This isn’t the case in soil unless you’re willing to transplant it, which comes with a whole set of other issues.
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Sweet Autumn Clematis Temperature & Humidity
The sweet autumn clematis is hardy to USDA zones 5 to 9. It can take temperatures down to -20 degrees Fahrenheit. Although, some gardeners will tell you that they can survive in zones 4b or even 4a which reach -25 and -30 degrees, respectively. Unfortunately, I can’t verify either for myself since I live in a warmer region.
In any case, the plant is “happiest” when it begins to get cold. During August and September, you’ll see it produce lots of fragrant blossoms that until first frost arrives. When winter comes, it’s time for the plant to take a breather at least until next spring.
Unlike houseplants, the clematis terniflora isn’t picky with humidity. So, this is one less aspect to consider when growing the plant.
Sweet Autumn Clematis Watering
Clematis terniflora needs about an inch of water per week. It isn’t a heavy drinker. However, it likes regular watering especially during the hot summer months.
If it rains regularly in your area, you may not need to do a lot of watering. However, it’s never a good idea to guess when it comes to watering. As such, I highly suggest getting a rain gauge which is fairly inexpensive.
This allows you to easily keep track of how much rainfall there has been in the past few days without any effort on your part. From there, you can easily supplement if needed.
However, the most important thing to remember is not to overwater it. This can be adding too much water each time, watering too frequently or using incorrect soil. All of which is cause waterlogged soil that will damage the plant.
Sweet autumn clematis likes moist, well draining soil. Slightly acidic soil with pH between 6.0 and 7.0 that’s rich in organic matter works as well.
But overall, the plant can tolerate different soil conditions. Your biggest priority here is to make sure it drains well.
Because of their penchant for moist conditions, clematis can be at risk of mold and fungal disease. The worst one of which is Clematis wilt which is aptly named for it. Since it doesn’t have a cure, prevention is essential. The good news is, as long as soil is kept well draining, it will rarely occur.
This means that it’s a good idea to amend the soil if needed. Compost is a great way to improve your garden soil’s draining ability. You can likewise add sand.
If you’re growing the plant in a pot, perlite is a good substrate to add to potting soil to get rid of excess moisture.
The last thing about soil is that keep in mind that the clematis terniflora is a climber at heart. As such, while you can let it grow as ground cover, it is best displayed growing up walls or vertical structures like trellis and arbors.
If you let it do so, make sure the setup is strong and sturdy. Since the plant gets up to 30 feet high, it will get heavy. Any weak scaffold will give way.
While were in the topic of displaying the plant, be aware that the plant is “top heavy”. That is, it is dense up on top with all its foliage and flowers. This makes it showy and very attractive.
However, at the bottom, it is fairly sparse and somewhat bare in comparison. As such, you’ll want to have something cover its “legs”, such that the base doesn’t look too blank.
Similarly, since its roots like coverage from the hot sun, you can use this opportunity to add ground cover (if you like nature) or garden décor (for man-made) to keep the base and roots cool.
Like many fast growers, the sweet autumn clematis is a heavy feeder. Thus, giving it a healthy dose of plant food will pay off when it starts to bloom between August and September.
Do keep in mind that in its first year when it is establishing its roots, it may not blossom at all. So, be patient and you will be rewarded in year 2.
That said, feed the plant regularly. Since its crowing glory are its flowers, you don’t want a fertilizer that’s high on nitrogen, the N part in N-P-K. This will cause increased foliage growth and less flowering. Thus, a 5-10-10 fertilizer during springtime once a month through its growing season works well.
Also, keep in mind that like water, too much fertilizer is a bad thing. Being lower in nitrogen helps reduce the risk of heavy salt buildup. However, overfeeding the plant or fertilizing it too often increases the risk of fertilizer burn.
This is a problem many new gardeners experience believing that more plant food means faster growth and larger blooms. Unfortunately, in this case, too much can be very damaging to your sweet autumn clematis.
Pruning Sweet Autumn Clematis
Sweet autumn clematis fall under pruning group 3. As such, there are a few things you want to do:
- Prune it after its blossoms fade late in fall
- Be aggressive. Hard pruning is in order.
The plant is an aggressive grower. More importantly, it will self-seed. So, left unchecked it can become invasive as the seeds get blown off by the wind to different areas of your garden and start to grow.
This is why you’ll see many people getting rid of their clematis terniflora like they do weeds.
Cut them back after they’ve bloomed by removing this seed heads. This will prevent the seedlings from self-sowing.
You also don’t have to worry about plant stress when doing so. In fact, you can trim them all the way back to about 12 inches above the ground without any problem. Come next spring, they’ll bounce right back.
The only exceptions to this is if you’re trying to let the clematis terniflora cover a wide area. For example, if you want to fill part of a large yard with ground cover or allow it to climb up something like a pergola.
Sweet Autumn Clematis Propagation
Because of its invasive potential dues to self-seeding, you’ll almost never see any gardener propagate this plant. The only exception is if they’re selling it or giving it away to friends.
In your garden, the plant not only grows fast, it has the potential to grow where you don’t want it to if you don’t aggressively prune the seed heads after it flowers fade in fall.
In fact, you’ll find more gardeners figuring out how to rid their garden of the clematis terniflora.
That said, the plant can be propagated via seed and stem cuttings.
- Seedling can be found around the plant. With these, you can just transplant hem to a different spot or into a container if you want to give them away.
- Stem cuttings are often the easiest way. All you need is to cut off a 4 to 6 inch long stem. Then plant it in potting mix to allow the plant’s to root and develop. This usually takes 1 to 2 months. From there, as the plant starts to sprout, you can decide whether or not to transplant it to your garden.
Sweet Autumn Clematis Transplanting & Repotting
The best time to start your sweet autumn clematis’ seeds are between late fall to early winter. You can them move the seedlings outside as long as the temperature doesn’t go below freezing.
When planting, make sure to give it enough space. This is key as the plant grows fast and big. It will get to about 15 to 30 feet high. And, it will spread sideways as well.
Thus, any plant that’s too near will be “taken over” by it.
Sweet autumn clematis are toxic to both plants and animals. Its sap irritates skin. And, while rarely deadly, if ingested can be poisonous. This can result in diarrhea, dizziness, convulsions and mouth ulcers just to name a few symptoms.
As such, it is a good idea to keep little children, dogs, cats and horses away from this plant. You’ll also want to use gloves when working with it, be it pruning or propagation, since it can irritate skin. Although, not everyone is affected by this issue.
Pests and Diseases
The biggest problems that sweet autumn clematis face is moisture related. This includes Clematis wilt, powdery mildew and fungal spots. Of these, the most deadly is wilt as it doesn’t have any cure. And, when it strikes, the plant’s leaves will look withered and have black spots.
The best way to avoid any of this from happening is making sure that the plant or its leaves don’t retain moisture for too long. Thus, you want to use well-draining soil. If your garden has heavier soil like clay, you’ll need to use compost or sand to improve its draining ability.
Clematis terniflora in containers are easier to fix as you have more control over the potting mix. And, you can easily repot it. However, maintenance is a little bit more difficult in containers because weather plays a larger role in how fast or slow the soil dries.
If any of these occur, you’ll want to use a natural fungicide.
As for its leaves, don’t water over the plant and soak its leaves. Instead, water on the soil. This will keep them dry. It’s likewise a good idea to keep them somewhere where air circulation is good. This helps any moisture to dry faster.
As for pests, the most commons ones include spider mites, earwigs, slugs and scale. Inspection is the best way to spot them early as you can see these bugs on foliage. Similarly, they’re work can be found in discolored or damaged leaves.
When you do find them, use insecticide to treat as soon as possible.