Clematis Paniculata (Sweet Autumn Clematis) How to Grow & Plant Care

Last Updated on October 31, 2021 by Phil

The Clematis paniculata is the second Sweet Autumn Clematis in we’ve covered. The first being the Clematis terniflora which also happens to go by the same nickname.

This is one reason why plants have botanical names. Since many different plants often have similar common names, there can be a lot of confusion among them. Botanical names are unique so you don’t have to worry about these overlaps.

In any case, it is important to distinguish between Clematis paniculata and Clematis terniflora because they are two different plants. The former, which we’ll go in depth to in this article comes from New Zealand. The latter is native to Asia, and found in Japan, China and a few other places in that region. Although some gardeners call it the Japanese Clematis because many come from this country.

In any case, the Clematis paniculata is a vigorous climbing vine that can grow up to 30 feet if not pruned often. Its growth habit is the reason why many people plant it under arbors, trellises, pergolas and walls.

The plant blooms in late summer and produces small to medium sized blossoms that are smaller than those of the more popular clematis varieties. But, what it lacks in size and bright colors, it makes up in fragrance and its beauty in number.

That said, as pretty as the plant looks, it is invasive in the warmer parts of the country (south). This is because it is a unisex plant with both male and female parts. This allows it to self-sow its seeds which can be easily blown by the wind from its seed head.

As such, pruning is essential after the flowers start to fade to prevent this from happening, as you’ll see below in the pruning section.

Clematis Paniculata Plant Care

Clematis Paniculata Light

The Clematis paniculata needs either full sun or partial shade to grow well. But, between the two, it thrives more in partially shaded or when it receives dappled light.

The plant is shade tolerant. This means that it enjoys between 2 to 6 hours of direct sunlight better than full sun which is more than 6 hours of direct sunlight a day

It likewise prefers having some kind of cover or canopy overhead that keeps it protected from the sun’s rays. However, it is crucial that even in shaded conditions, the plant should be getting bright light.

The reason for this is that your sweet autumn clematis likes to get a lot of sunlight. But, it also likes to keep its roots cool.

As such, you can place it in the east, north, south or west with a few conditions.

In the north, it will enjoy shaded conditions. But, you need to make sure that there is enough light to keep it happy. If there isn’t enough light, it will slow down your plant’s growth as well as its ability to produce beautiful flowers.

An east facing position is very good because it receives gentle morning sunlight. Here, it avoids the harsh afternoon sun. And, easily gets 6 hours of direct and indirect sunlight daily as well.

In the west and south, you want to be more careful because they’re exposed to the mid afternoon sun. If you live in a hot climate region or experience brutal summers, you’ll need to keep it well protected during these times.

Clematis Paniculata Temperature & Humidity

The Clematis paniculata is a long blooming plant. But, it cannot stand overly cold or warmer conditions. It is hardy down to -35 degrees Fahrenheit. And, will be happy as long as the temperature doesn’t go above 20 degrees Fahrenheit.

Thus, the best places to grow it outdoors is in USDA zones 3 to 8.

Due to its need to keep its roots cool and its need for sunlight, it is a good idea to use mulch to help regulate is temperature.

In warmer months, adding a healthy layer of mulch protects is base from direct sunlight and the heat that comes from. It also helps with water retention to help keep your plant hydrated. You’ll likewise want to adjust the amount of mulch depending on the time of year and climate.

During the colder months, mulch protects it from frost.

Watering Clematis Paniculata

The Clematis paniculata is fairly low maintenance when it comes to watering. That is, it isn’t a thirsty plant that requires a lot of attention in this area.

However, because of the importance of watering for growth and the risk of overwatering and moisture problems, you want to take extra care here.

The sweet autumn clematis, like other plants in its genus, is prone to powdery mildew, leaf spot, root rot and Clematis wilt. All of which stem from overwatering or allowing moisture to sit, be it around its roots or its foliage.

Similarly, because you can’t afford to let the plant go dry, it is essential to be vigilant in this area.

That said, the Clematis paniculata needs about an inch of water every week. This is cumulative of both rain and irrigation. During the dry, hot months, it will need more.

Deep watering also allows it to grow optimally. This means you don’t want to just wet the soil and go on to the next plant. Instead, you want to slowly water it to allow the soil to soak in the moisture. Doing so allows the liquid to reach its roots.

In line with keeping its roots cool, you can use mulch, shallow rooting ground cover or stones to cover its base. While all work, mulch is a great option since you can control exactly how much to use and the kind of material to use. Additionally, it helps retain moisture.

Soil

Clematis paniculata needs moist, well draining soil to thrive. For the best results, give it rich, fertile soil with neutral pH.

That said, you don’t have to stress too much if your garden’s soil’s quality or its pH isn’t exactly what the plant needs. The plant can tolerate also most any kind of soil from clay to sand. And, it doesn’t fuss too much about soil pH as well.

However, because it is prone to moisture problems that lead to disease, well-draining soil is crucial. This means that you may want to add compost or sand into the hold to improve its drainage before planting the Clematis paniculata.

That said, your sweet autumn clematis does not like dry soil. Nor does it like wet, soggy soil. So, keeping it constantly moist is idea.

Like other clematis plants, it needs a lot of space. Thus, you’ll want to dig a big enough hole when planting or transplanting into the ground. Ideally, leave 3 to 6 feet between plants because of its ability to reach between 20 to 30 feet and 4 to 6 feet wide.

Finally, don’t forget to grow it close to a vertical structure. The plant needs some kind of support to grow properly. It climbing nature also makes it look best when allowed to go up. Due to its size, having a high fence, trellis, arbor or wall is ideal.

If you live outside of zones 3 to 8, you can grow the plant in a container as well. Clematis paniculata do well in pots although they won’t be able to grow as big as they would in the ground (which may be a good thing anyway).

In containers, you want to use well draining potting mix and have drainage holes at the bottom. You can likewise use perlite to improve the soil’s drainage if needed.

Fertilizing

Your Clematis paniculata is a heavy feeder. It needs sufficient supplementation in order to produce it lovely, fragrant blooms. However, because you want it to focus on its blossoms, using a low nitrogen fertilizer is best.

Nitrogen promotes leaf growth. As such, it is the main ingredient for lawns and foliage plants. If you use a high nitrogen fertilizer on your clematis, it will divert is growth from its flowers to the leaves. This is something you don’t want because the plant’s flowers are its main attraction.

So, during its growing season, apply a 5-10-10 plant food once a month. Once the buds reach about 2 inches in size, you can alternate between a 5-10-10 and a 10-10-10 (balanced) fertilizer for the rest of the growing season.

Clematis Paniculata Pruning

Sweet autumn clematis belong to pruning group 3. This means that it blooms later in the summer on this season’s growth.

Thus, the best time to trim your Clematis paniculata is later in winter or early in spring before the new growth starts coming out. You also want to be aggressive when pruning (hard pruning). Cut the plant back to about a foot from the ground leaving a couple of healthy buds.

When trimming, make sure you also remove old, dying or dead leaves and stems. Similarly, cut back discolored or damaged sections as well.

Since the plant is a vigorous grower, it can cover objects and spaces that you don’t want it to. You can likewise prune its vines by the handful.

The Clematis paniculata doesn’t mind heavy pruning so you don’t have to worry about taking off bunches at a time.

Another important thing to consider is that the plant is invasive in certain areas. It is notoriously known for self-sowing its seeds which allows it to propagate all of your yard or garden without your permission. In doing so, it takes up areas you’ve allotted for other plants.

The best way to prevent this from happening is to trim is right after it blooms preventing the seed heads from having a chance to disperse the seeds via the wind.

Propagation

As mentioned above, the Clematis paniculata is a vigorous self-sower. As such, many people don’t necessarily need or want to propagate it. This is less of a problem in the colder parts of the country (northern states), because the plant isn’t hardy to low winter temperatures there.

But, if you live in the warmer or southern part of the country, the wind easily carries the plant’s seeds making them invasive.

That said, there are a few ways to propagate the plant if you want to grow more of it. These include stem cutting, layering and from seed.

Of the three, stem cutting is the easiest. It is also much faster than propagation from seed, which takes the longest time because it has to germinate.

source: wikimedia commons

How to Propagate Clematis Paniculata from Stem Cuttings

The best time to propagate is during spring and before summer ends.
Take 3 to 4 inch stem cutting. Choose a stem that is healthy and has a few leaves but no flowering shoots.
Then, plant it into soil and place it in a warm, humid location.
Water the soil to keep it moist.
Within 1 to 2 months it should start rooting.
Once it starts outgrowing the pot (you’ll see roots come out of the drainage holes), it is time to move it to a larger container. You can likewise transplant it into your garden.
Don’t expect it the flower during year 1. You’ll likely see it begin to bloom late in year 2.

Transplanting & Repotting Clematis Paniculata

The best time to transplant your Clematis paniculata into the ground is during springtime. You can pick one up from your local nursery.

Because the plant can tolerate different soils and different pH levels, you can plant it almost anywhere. Although, rich, fertile soil and a neutral pH gives you optimum growth.

When choosing a spot for your sweet autumn clematis, keep in mind a few things.

Lots of light. This can be full or partially shaded sunlight. The latter is preferred especially in warmer areas. But, keep its roots cool.
Well draining soil. While the plant doesn’t mind the type of soil, it is susceptible to fungal infections. Thus, well draining soil is essential to avoid the problems that come from that.
Nearby vertical space or structure. The plant will need something to support it early on. And, it likes climbing up things as it gets bigger. Since it can grow to between 20 and 30 feet high (you can prune it to limit it size though), the wall or structure will need to be big enough and strong enough to support it when it gets larger.

Once you have all those things ready, it is time to plant.

Dig a hole that’s big enough to fit the plant.

Also make sure it is deep enough. You’ll want to plant the crown at least 2 to 3 inches below the ground. This will:

Protect the roots from the sun.
The extra layer of soil also protect dormant buds keeping them safe as backup in case the stems don’t make it.
It also allows new shoots to grow from the ground which helps it recover in case Clematis wilt hits.

Once the plant is in place, backfill the hole with soil. Add mulch around it to help keep its base (and roots) cool. If the location gets a lot of direct sunlight, you may also place stones to cover the base area from the sun’s rays.

Toxicity

Clematis paniculata is highly toxic. This includes its leaves and sap. So, it is a good idea to keep young children, dogs, cats and horses away from it for fear of chewing or ingesting any of the plant.

Doing so can cause lots of unpleasant and dangerous symptoms include fainting, convulsions, vomiting, and diarrhea.

Similarly, because the sap can cause skin irritation in some people, it is a good idea to wear gloves every time you prune or propagate it.

Pests and Diseases

The Clematis paniculata is a fairly resilient plant. But, it is susceptible to fungal disease and Clematis wilt. Both of which are caused by too much moisture that doesn’t dry or drain fast enough.

This makes it very important to plant it in well draining soil and not to overwater it. Similarly, planting the crown 2 to 3 inches below the soil surfaces helps protect it from wilt as new shoots grow from beneath the ground.

If either of these happen, you need to immediately prune away the dead or dying sections. Make sure to throw them away safely so they don’t affect any of your other plants. You also don’t want to use these leaves for compost.