Some years ago, C. patens 'Yukiokoshi ' was the first large flowered species clematis that I had the opportunity to add to my collection. Like many gardeners new to the genus, my beginnings in clematis about 15 years ago involved the purchase of hard-to-establish type 2 large flowered hybrids, including some "doubles". Based on my experience with some of those plants at that time, I assumed 'Yukiokoshi' was yet another diva. ©Shigeharu Matsuda ©Shigeharu Matsuda From the first growing season, C. patens 'Yukiokoshi' started teaching me how resilient and vigorous even large flowered clematis species can be. While I had already experienced this with some other clematis species, I was very surprised that a large flowered clematis with a multitude of sepals would be an easy, vigorous plant.
My fear of patens diminished in parallel to my experience curve and eventual belief that most clematis species plants, grown in reasonable conditions, out perform most hybrids.
The word origin of patens refers to the plane of the sepals and the fact that they are at a right angle to the stem.
Thanks to research and translation by plantsman and friend, Shigeharu Matsuda, the following summary of the history of the plant was able to be confirmed see Ref 1.
Kazaguruma, which refers to the collective selections of C. patens in Japan, are distributed from Honshu to Kyushu as well as the Korean peninsula and Northeast China.
Selection, and possibly breeding, in the Edo period (1603-1868) resulted in the double form of forma alba Makino (white Yukiokoshi) and forma coerulescens Makino (pale purple Ruriokoshi). These species were introduced to Europe by botanist P.F. Seibold in 1836 and further used for hybridizing. Additional documentation of the ancient presence of the white double form Yukiokoshi is found in a classic botanic booklet, (a supplement to Chikinsho, 1733).
Ruriokoshi©Shigeharu Matsuda Kazaguruma©Shigeharu Matsuda ©Deborah Hardwick Despite this incredible ancestry, 'Yukiokoshi' is a diva in appearance only. The plant has taught me many lessons in cultivation. From the first season the plant surprised me with early, vigorous spring growth and blooms, followed by attractive foliage and re-bloom with little coaxing. One spring, old growth on the plant was hopelessly entangled and with great trepidation I did a relatively hard prune after the first flush of blooms. My expectation was that the plant's inner diva would take some time to respond, regrow slowly and hopefully be able to bloom the following spring.
Imagine my delight when regrowth was fast, and the plant commenced to a second blooming in early summer! Over the years, the plant's tenacity has emboldened me. We usually start spring with last year's growth intact, and the plethora of early blooms are truly something special. Most years I do a late spring pruning so that I can see another flush of blooms. With just a tidy up after that, the plant almost always produces another flush as summer wanes. Frankly, while some of the double cultivars give a fantastic showing on established wood, I did not at that time have any double cultivars that shared this vigor, bouncing back to bloom again and again. In my years of growing 'Yukiokoshi', the plant has never bloomed with a single form, even on the newest wood.
The posture of the upright flower buds is an early spring hallmark on patens species and cultivars. Leaves are ternate, often with 3 lobed leaflets and a manageable 2 meters (6.5 ft.) in height, making the clematis suitable for many garden situations. Twining petioles help the plant adapt to a variety of supports. The thin stems are wiry and strong; showing a dark red coloring on younger as well as older, more weathered growth. Achenes are broad, and pointed in shape with long silky, yet feathery fruit tails. One of the most distinguishing hallmarks of Japanese patens selections is the 'gappy' attachment of the sepals, which are a characteristic which can identify patens genetics in hybrid plants.
The bloom color is as spectacular as the form and vigor, and ranges from creamy white tinged green, to bleached linen white with beige tips on the sepals on older blooms in full sun, to touches of a blush hue in the cooler temperatures on late blooms.
And just when you thought there were no more attributes to be shared about 'Yukiokoshi', there is another compelling reason to grow this clematis. It loves being grown in containers as much as in the garden.
Recently and coincidentally, I obtained a small plant of 'Yukiokoshi', which arrived bare root. I am eager to compare it to the one that I have had growing here for years, but it shows already the vigor and will to bloom, as evidenced by the photo below of the small plant in bloom within 10 weeks of being potted up.
Please do not misinterpret my love of species clematis as disdain for hybrids. Hybridizing brings breathtaking color, form and diversity to the genus, and I collect and grow hybrids, as well as species, avidly. However, there are hybrids that do not demonstrate the plant qualities of their ancestral species, especially in the category of large flowered, double flowering plants.
I guess the bottom line for me is that when you know what some clematis plants are capable of, that becomes the gold standard by which both species selections and hybrids should also be measured. Clematis patens 'Yukiokoshi' is that gold standard indeed.
"My small C. 'Yukiokoshi'"
- Study on classification of clematis and the cultivars  - Characteristics and distribution of species and history of cultivar development
Takashi Hosoki, 2010. Agriculture and Horticulture Vol 85, No 6, P 656-671
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