Clematis for Partial Shade Sites

Posted by clematis on Wednesday, June 4, 2014

We often get asked about which Clematis will do best in a north facing location or partial shade garden site.

While most clematis require at least a half day of sun, this handout provides a list of many clematis that will do well in the part shade garden.

Download: Clematis for Partial Shade Sites

Starting Clematis From Seed

Posted by clematis on Wednesday, November 24, 2010

At the Rogerson Clematis Collection we have been starting rare and prized clematis species from seed for many years. We have prepared a nine page step-by-step instruction guide, with pictures, on how we do it at the Collection.

Starting Clematis From Seed

View Starting Clematis From Seed. This is a PDF which you can read now or save for later reference.

A Muddle of Montanas

Posted by LindaB on Monday, November 1, 2010

To avoid the risk of losing the logic of my copious notes from the lecture given by tenacious plantsman Christopher Sanders for the International Clematis Society conference on Portland, I will distill them here along with my ruminations and their implications for the Rogerson Clematis Collection (RCC). I use the word “distill” advisedly, as you may feel tipsy after you read all this. Chris’ topic was the Montana Group species and cultivars, and his revelations were just as iconoclastic as his talk on the Orientalis/Tangutica Group in Dublin 2006.

In the Case of the Montana Group, its origins to horticulture are steeped in myth, some of which was sorted in the late Dr. John Howells’ book, The Montanas, in 2004. Chris verifies Dr. Howells’ scholarship, and we can now rest assured that Clematis montana (a white form) was first documented by Buchanan in 1802, not in 1827 as is widely put about. Although common in some areas, Clematis montana var. rubens was not introduced to cultivation in Europe until nearly 100 years later by E. H. Wilson.

Chris limited his comments to taxa in the Montana Group which he had experience of during his years with Bridgemere Nurseries in the UK, or has observed in the wild. He showed a terrific form of Clematis montana subsp. praecox var. praecox which has bright red filaments and connectives (if you look closely at the anthers of any clematis, you will see that the anthers have two lobes held together by tissue known as a connective) contrasted by bright yellow pollen. I do not believe this taxon has ever been in the RCC, but it is a sharp-looking flower, to be sure. He also showed an intriguing image of C. montana subsp. montana with a noticeable pink bar on the reverse (outside) of an otherwise white flower. The RCC does have a close cousin of the species montana, in C. gracilifolia, which has earlier, smaller flowers. The pictures of these three species variants were taken in 1993.

Clematis gracilifolia

In 1995 Chris was again in China, in a nearly subtropical region of southeast Tibet, in an area noted for deep sheltered gorges. There he saw Clematis montana subspecies montana var. sterilis, with slender sepals, from pink buds leaving a pink reverse on the open flower. This taxon has very pointed foliage. He also saw a C. montana subsp. montana var. grandiflora form with a distinctly picotee edge (an outline) of pink on a large white flower. This coloration grew more pronounced as the flowers aged. The foliage was also distinct, the leaves having tufts of five to six leaflets, with entire margins free of any serration.

Clematis grandiflora

Chris commented that the newest edition of The Flora of China calls Clematis montana subsp. montana var. grandiflora, var. longipes instead now, but if he mentioned why, I didn’t catch it. Perhaps clematis registrar Duncan Donald will be able to answer that for us. He also noted that the Flora describes C. tongluensis (another Montana cousin, which has never yet flowered in the RCC), has very slender sepals, and brown anthers on white filaments. This is something to look forward to if we can keep it alive!

At last Chris waded into the deep end of the confusion surrounding Clematis spooneri, C. chrysocoma var. serricea, and C. montana var. wilsonii. Hold onto your hat. There has been general agreement for years that C. chrysocoma, while often seen and photographed by modern botanists in China, is not in wide cultivation, so there is no great movement of the earth there. However, Chris contends that in the current market, plants sold as C. spooneri or its synonym C. chrysocoma var. serricea are actually Clematis montana subsp. montana var. grandiflora (or var. ‘Grandiflora’ if you wish). This is the sort of revelation that causes clematis curators to awaken with the yips in the night. In the RCC we have both C. spooneri and C. m. subsp. m. var. grandiflora, so I will be observing both carefully in April and May of 2011.

Clematis 'Jenny'

The mother of all muddles is the confusion surrounding Clematis montana var. wilsonii. Most of the cultivated plants available with this name are incorrect, either due to a name switch at some earlier time, or because open-pollinated seedlings were sold as a sure thing. Chris has identified four characteristics which must be present to correctly call a clematis “var. wilsonii“. First, as originally described, var. wilsonii had little or no fragrance. That’s right, read it again: little or no fragrance. Now doesn’t that knock you hat in the creek? These days the heady aroma of hot cocoa is said to be the hallmark of thia taxon, but no, that is not how E. H. Wilson experienced the type specimen in the wild. Secondly, it must flower well after the other Montana Group members, not just a little later than the other white forms. C. montana var. wilsonii starts flowering in early July at the earliest. It may continue randomly flowering until late September.

The final two criteria for a true var. wilsonii are an otherworldly boss of stamens nearly as long as the sepals and puffed out like an angry cat. Lastly, the foliage is unusually bullate (lettuce-like), with deeply incised veins which are raised on the underside of the leaves. Brewster and I have long felt that the Clematis montana var. wilsonii of horticulture is not right, more because of the timing of the bloom than for any other reason. However, the RCC boasts two plants, separate collections by Dan Hinkley in the same area of west Sichuan where Wilson made his collections, that just may be the real thing. In fact, I am so confidant that the specimen we have growing in Rosa moyesii ‘Geranium’ is right that I dashed out after Chris’ talk and took cuttings. Our second likely contender fully occupies that last row (18 feet) of the test garden, and will be closely observed in 2011.

Mont 'RubSuperb'2.jpg

Chris stated that Clematis montana var. wilsonii ‘Peveril’ shows very little difference from var. wilsonii. Most of us who have this plant got it through Exuberant Gardens, the clematis nursery of Dorothy and David Rodal, in business in the late 1990s through 2001. Chris Sanders was able to see the Rodal’s plant, still in a fair amount of bloom on September 13, 2010, and make a positive identification: little scent, fancy leaves, fancier stamens, and continuous bloom from mid-summer onward. Their plant of var. wilsonii, however, has an immodest amount of scent.

Clematis 'Fragrant Spring'

A couple of final notes: the plant Roy Lancaster brought into the trade as Clematis spooneri or “the Chrysocoma Hybrid” had pale pink, not white, flowers, and slightly hairy leaves. Here in the U.S. this clematis seems to have dropped out of commerce. And most disturbing to me, Chris reports that Clematis montana ‘Continuity’ has pink flowers with long pedicels, a long period of bloom, and a bold crown of stamens with bright gold anthers and pollen. Sadly, the RCC plant is clearly misnamed, with white flowers and foliage distinctive with a pale variegation highlighting the mid-vein of the leaves. What the devil is our plant?

Ever notice about plant experts that they can muddy the waters yet calm them at the same time? If Chris Sanders weren’t such a thorough scholar and erudite lecturer, one wold be tempted to be annoyed with him. However, the genus Clematis is, in fact, blessed that have a plantsman in our midst who is willing to take on the years of sloppy nomenclature and get it sorted. Now if we could just get the commercial growers to take more care, perhaps the gardening public would feel less intimidated by this fascinating genus.

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