Clematis courtoisii Hand.-Mazz.

Clematis of the Month for April 2020

described by Ton Hannink

C. courtoisii©Ton Hannink

Section: Viticella

Subsection: Floridae

Species: Courtoisii

Distribution: China Anhui, SE Henan, E Hubei, E Hunan, S Jiangxi, N Zhejiang.

Named after: Père P. Courtois, French missionary in China. He collected plants in the province of Jiangxi and Anhui and was linked to the Museum in Zi-Ka-wei.

Flowering: April - June

Habitat: Forests, slopes, along streams; 200--500 m.

First Recorded: Handel-Mazzetti, Acta Horti Gothob. 13: 200. 1939-. 1940.

Flowers: Single and flat, diameter is 8-12cm (3-5 inchs), color white, but sometimes the flowers tinged purple.

Tepals: 6, 3-5cm long (1-2 inches).

Anthers: dark violet and 1.5-2 cm long.

Pistels: dark violet.

Seeds: big, plumose and germinate very well after 2–6 months.

Height: about 2–3 meters (6-9 feet).

Until I got my first young plants from China, I had no idea about the properties of this species. The only information was that this species was almost the same as C. florida. So, with this information I had to wait but I was glad to have this rather rare species, one that, at this time, was unknown in Europe and the USA. This species could be very interesting for hobbyists.

When the first leaves appeared, I had my doubts about the species because the leaves were much bigger than leaves from C. florida. The plant grew very well and after 3 months the first buds appeared. The outside of the buds was greenish.

It was a big surprise when the flowers opened because the anthers were very long, I had never seen such a long dark anthers in a Clematis species.

The anthers have dark pollen. I have only seen this before in one C. patens from Japan, though it was not as dark.

The flowers are pure white, though sometimes there is a little purple in the centre of the flower.

C. courtoisii is very useful as a pot plant. After flowering you can prune back the plant and after three month it will flower again. In this way you can have three flowerings in one year. As a pot plant, it needs fertilizer during the growing and flowering periods. In spring and summer, C. courtoisii needs enough water.

In countries with mild winters, this species will survive outside so that you have a lot of white flowers in your garden. In winter, this plant needs a rather dry place in the garden

Hardiness: I have my doubts about the hardiness of C. courtoisii and I have not tried a test in my garden, perhaps I will in the future. I stored some plants in an unheated greenhouse over winter, though, and they survived.

Pruning can be done to keep the plant small and get more flowerings. Therefore you must prune the plant very hard in autumn. In spring, you get a lot of new stems. On the new stems you get buds and later the flowers. The older the plant, the greater the number of beautiful flowers.

Propagation by cutting is more difficult than C. florida but the plant gives many seeds and they germinate within three months. You must pollinate by hand and you must protect the flower so that it cannot be pollinated by bees.

I have made a lot of crosses with C. courtoisii. They have not been done before and the results are plants with white flowers but also new colors in the Clematis world.

Note: In some publications is said that the Florida group has non plumose seeds but that is not true. C. hancockiana and C. courtoisii have plumose seeds.
C. courtoisii seedling©Ton Hannink

C. courtoisii seedling

C. courtoisii leaf©Ton Hannink C. courtoisii leaf©Ton Hannink

C. courtoisii leaf

C. courtoisii leaf

C. courtoisii bud©Ton Hannink C. courtoisii bud starting to open©Ton Hannink

C. courtoisii bud

C. courtoisii bud starting to open

C. courtoisii - a mass of flowers©Ton Hannink C. courtoisii showing the flat flower©Ton Hannink

C. courtoisii - a mass of flowers

C. courtoisii showing the flat flower

C. courtoisii flower close-up©Ton Hannink C. courtoisii flower close-up©Ton Hannink

C. courtoisii flower close-up

C. courtoisii flower close-up

C. courtoisii seedhead©Ton Hannink

C. courtoisii seedhead

C. xiangguiensis (left) and C. courtoisii (right)©Ton Hannink

C. xiangguiensis (left) and C. courtoisii (right)

Ton Hannink Ton Hannink

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