What is so unremarkable about Clematis 'Jackmanii'?

When it comes to ornamental flowering vines in horticulture, if the genus Clematis were to take second place, no other plant would deserve first.

Today's protagonistClematis 'Jackmanii', in the narrow sense refers specifically to the hybrid C. × jackmanii cultivar "Jackmanii". Its flowers are very large, with 4 sepals, deep purple. Compared with the endless stream of modern hybrid new cultivars, 'Jackmanii' looks somewhat unremarkable, at least not matching my aesthetic. But its status is extremely high; it can be said to beone of the most important foundations of large-flowered clematis horticultural cultivars。

Today's protagonist - the unremarkable "Jackmanii". Image: learningwithexperts.com

I am not particularly obsessed with clematis; part of my fondness for it comes from my love of the Ranunculaceae. Over four years I have only grown a few easy-to-grow cultivars, about a dozen plants, and my cultivation methods are rather extensive. Rain protection, shade, drainage, fertilizing - nonexistent; I basically rely on the heavens. Fortunately, only one small seedling died in the first year. The rest, although blooming only a scant few flowers each year, still contribute some beauty to the yard.

Some cultivars I have grown; I cannot even name the cultivar names. Image: Frost Moth

Clematis in All Its Variety

Clematis hasextremely rich flower shapes, colors, and plant heights, and their blooming times also differ.If cultivars are matched appropriately, they are enough to support a vertical flower border in one space from early spring to late autumn. Some have brilliant flower colors and intricate flower shapes, appearing noble and magnificent; some are icy-boned and jade-like, plain and elegant; some have small flowers in great numbers, dotting like a waterfall of flowers rushing downward; some have flower shapes like little bells, delicate and cute; some have particularly long tepals spreading outward, like birds spreading their wings.

Clematis 'Petit Faucon' C. "Petit Faucon". Image: naturehills.com

Historically, the status of clematis was certainly not as high as that of roses, and even less than some herbaceous flowers. It mostly appeared as a rural wildflower, such as the European native C. vitalba, a wild vine reaching over ten meters long, bearing very ordinary small white flowers, with an alternative name "traveller's joy".

In the mid-16th century, from southeastern EuropeItalian clematisC. viticella was introduced to Britain; by the end of the 16th century, this clematis already had two cultivars of different colors. Over the following 100-plus years, although several wild clematis species from Europe, Asia, and North America were developed as garden plants, such as C. integrifolia, C. orientalis, and the bell-flowered C. viorna, none were large-flowered clematis, so they did not play a core role in breeding at that time.People hoped to find more large-flowered clematis like Italian clematis to participate in breeding。

China has more than 100 species of clematis,accounting for more than one-third of the world's species, among which there is no lack of very showy large-flowered species, but they never managed to occupy a place in ancient Chinese horticulture. Instead, neighboring Japan often used clematis in horticultural cultivation.

In 1776, the first Swede to reach Japan - naturalist Carl Peter Thunberg - discovered the large-flowered C. courtoisii, native to China, in Japan and brought it back to Sweden, after which it was mistakenly identified as C. florida.C. courtoisii has white sepals and deep purple stamens, creating a very strong visual contrast. In European breeding it formed a category of its own, and its derived cultivars are called the Florida group (F group) clematis.

The native large-flowered C. courtoisii, full of ethereal beauty. Image: aagesenshave.dk

Jackmanii Surpasses Its Parents

The 19th century was the golden age of clematis breeding. In 1835, Henderson, a gardener at the Pineapple Nursery in London, successfully bredClematis 'Hendersonii'C. × diversifolia "Hendersonii" by crossing Italian clematis and C. integrifolia. This cultivar was very popular and also became an important parent for other hybrid breeding.

Clematis integrifolia 'Blue Ribbon'. Image: pinterest.com

During this period, two large-flowered clematis species from China - C. patens and C. lanuginosa - were introduced to Europe. In 1858, a gardener in Woking, EnglandGeorge Jackmancrossed C. lanuginosa with a red cultivar of Italian clematis, C. viticella "atrorubens". Thus the world-famous 'Jackmanii' was born. (Some experts also believe that the parents of 'Jackmanii' are C. lanuginosa and Clematis 'Hendersonii'.)

C. lanuginosa, an important foundation of modern hybrid large-flowered cultivars. Image: biolib.cz

As soon as 'Jackmanii' appeared, its spotlight overshadowed 'Hendersonii' and it quickly became synonymous with large-flowered clematis. 'Jackmanii' received the Royal Horticultural Society's First Class Certificate in 1863,and is called one of the most outstanding hybrid clematis of all time. Afterward, gardeners around the world used 'Jackmanii' as a foundation to breed many excellent large-flowered hybrid cultivars.

According to flower size, clematis can be divided intolarge-flowered(diameter 5-29 cm) andsmall-flowered(diameter 1.5-18 cm). According to flowering period, these two are further divided respectively intoearly-flowering groupandlate-flowering group, and each group is further subdivided into different sections.

'Jackmanii' belongs to the late-flowering large-flowered type, generally blooming from midsummer to autumn. Its vines can climb to 3 m high, and flowers can reach 18 cm in diameter. When covered in purple flowers, it becomes the focal point of the yard, yet it does not take up too much space (many small-flowered clematis do). As mentioned earlier, the unremarkable 'Jackmanii' is only one cultivar of C. × jackmanii,and there are other cultivars as well, not limited to purple and four sepals。

Jackmanii's white double-flowered cultivar "Alba" looks like a completely different flower from the original. Image: pinterest.com

Unstoppable Clematis Wilt

'Jackmanii' brought prosperity to large-flowered hybrid cultivars, but also brought the nightmare of clematis -clematis wilt. Clematis wilt is caused by fungi andcannot be prevented. It mostly occurs at the turn of spring and summer, when it clears after rain and the temperature rises rapidly;the aboveground parts of infected clematis rapidly wither and die without warning. If it is a potted clematis, the underground parts may also be infected, causing root rot.

One of the parents of 'Jackmanii', C. lanuginosa, is considered extremely susceptible to infection by the clematis wilt fungus. In the early 20th century, cultivars with Jackmanii bloodlines were infected one after another, affecting almost all large-flowered cultivars and once causing clematis breeding work to collapse.Gardeners introduced various disease-resistant native clematis for hybridization and grafting, but were never able to control clematis wilt.

Usually,deep planting is a traditional method for dealing with clematis wilt, that is, when planting, do not cover the soil only up to the top of the roots, but dig deeper,until the soil covers about 10 cm above the roots. Because most clematis wilt only infects the aboveground parts, and the lower axillary buds protected by soil can sprout again. However, according to the experience of domestic clematis experts, in hot and rainy areas, such as Jiangsu, Zhejiang, and Shanghai, deep planting instead increases the incidence of clematis wilt.

Clematis wilt cannot be prevented; you can only deal with the diseased and dead branches early, pruning downward until the diseased tissue is completely removed, so as not to infect other healthy branches, and then go out for a meal and adjust your mood. Image: blogspot.com

Clarify Habits Before Pruning

According to flowering habits, clematis can have three types of pruning methods. The pruning method is very important;for some groups, proper pruning can increase the amount of flowering, while improper pruning will result in no flowers to see that year。

Pruning Type 1includes many small-flowered clematis. This type is rather special: they only bloom on last year's old branches, soyou absolutely must not give in to itchy hands. Pruning is mainly for appearance;just cut off diseased and weak branches, spent flowers, and dead leaves。

Clematis montana var. rubens belongs to the Type 1 pruning Montana Group, also called the montana group, a vigorously growing small-flowered type. Its earliest parent is C. montana, native to China. Image: egardengo.com

Pruning Type 2generally applies to early-flowering large-flowered clematis, such as the most common 'The President'. This type of clematis blooms in April in spring, with flowers on flowering shoots growing from the axillary buds of last year's old branches, so it needslight pruning before the start of spring, retaining old branches as much as possible, and cutting back to the strongest pair of axillary buds。

C. "President" is a very easy-to-grow entry-level practice cultivar. Image: waltersgardens.com

The late-flowering large-flowered 'Jackmanii' belongs toPruning Type 3method. This type of clematis only blooms on new branches of the current season, so before the start of spring,the old branches from the previous year should be hard pruned, leaving only three to five nodes aboveground, to promote new branches sprouting from the roots。

Illustration of the three pruning types: Type 1 basically needs no pruning, Type 2 light pruning, Type 3 hard pruning. Image: pinterest.com

As the most diverse ornamental climbing plant in horticulture, clematis has always been one of the most popular flowers. Whether it is a large rural garden or a small balcony with insufficient light, there is a suitable cultivar.

Onlinereputable shopswhen selling clematis cultivars,will definitely indicate its group and pruning method. If the seller cannot answer this, then you need to look carefully at where the shop address is.

This article is the 168th article in the 4th year of Species Calendar, from Species Calendar author @Frost Moth.

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Ranunculaceae, Ranunculus asiaticus