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.
View Starting Clematis From Seed. This is a PDF which you can read now or save for later reference.
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.
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.
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.
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.
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.
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.
It is silly to be infatuated by potting soil, but we are. Thanks to Dave Andrews and the magicians at Pro-Gro Mixes & Materials, FRCC now has eight yards of our custom blended potting soil, perfect for clematis in containers. When the collection was housed at Gutmann Nurseries, the generous Bob Gutmann allowed Brewster and his volunteers to experiment with soil blends, using raw materials the nursery kept on hand.
Brewster suggested we blend our own mix after getting a shipment of happy little clematis plants from LaPorte Avenue Nursery in Ft. Collins, CO. The plants, mostly Colorado natives, arrived in a gritty soil with amazingly well developed root systems. It occurred to Brewster that most clematis would enjoy a coarser soil mix, and that such a mix might hold up better than regular potting soil, which starts to degrade and acidify, becoming “wet chocolate cake”, after only a year or two.
Gutmann’s basic potting soil from Pro-Gro is the #9B blend, containing some bark, pumice and a touch of peat moss. Our favorite blend (pretty much perfected by volunteers Rick Meigs and Sharon Kaito) starts with 50% Pro-Gro #9B, to which we add: 25% pumice (chunks the size of kitty litter), 15% coir fiber (coconut fiber), and 10% washed sand. The resulting alchemy is gritty and sturdy, not light and fluffy, and if I were clematis roots, I would love winding my way through it. Imagine stretching and having your back scratched at the same time, while being comfortably moist but not drowning. Mmmm…
FRCC now uses this soil blend for all of our potted clematis, including those we sell. We have also started using this soil in our “weaning” blend, the soil that newly rooted cuttings are moved into when they come off the perlite. Our weaning blend is now 33% coir fiber, 33% perlite, and 33% our potting soil. This is topped with 1/4 inch of #2 poultry grit, to keep the soil surface clean and move water away from developing crowns. (Don’t use the finest, #1 grit, as it has fine particles that can form a crust on the soil surface.)
If you have a nursery in the Willamette Valley or SW Washington, and need custom blended soils, let us recommend the folks at Pro-Gro. And if you need a lot of good soil for growing clematis in containers, just call ‘em up and ask for the Rogerson Clematis Collection mix. Visit their website,
www.pro-gromixes.com for more information.
Here at the Rogerson Clematis Collection we have a lot of combined experience in clematis propagation. Our board President, Sally Geist, is a long time practitioner of clematis propagation by semi-hardwood cuttings and from seed. Of course we have Brewster’s experience to draw upon, and in the summer of 2008 we had an avid intern who tried many methods and media. Sally and I learned even more on our visit to Japan with the International Clematis Society, also in the summer of ‘08. Sometimes tricks are needed, and an example is knowing, thanks to Mikioshi Chikuma of Japan, that Clematis integrifolia and its near hybrids are more successfully propagated when tip cuttings are used instead of older semi-hardwood.
We’ve learned that timing can be quite different for each horticultural group. For large-flowered hybrids, for instance, our best success is using stems that are about to bloom. This seems heartless, but their growth hormone is highly concentrated in the stems then, and even difficult cultivars are easier. With montanas, nearly anytime of year after the leaves have matured but before they fall in the autumn is okay. In any case, cuttings should be taken from young healthy plants.
Through trial and error we have begun using deep “tomato plug trays” to hold the cuttings, and each tray it set into a plastic flat lid used in this case to hold bottom water. The plug tray is filled with straight propagation-grade perlite. Internodal cuttings are cut to be, ideally, 2.5 inches (6.25 cm) long, so that the cut end is well down into the perlite and the leaf node sits right at the surface, to stay moist. We use Wood’s Rooting Compound as our hormone. It is a formula developed by Ed Wood, a bonsai specialist who had a nursery in Aurora, Oregon. It does not need refrigeration, and the type of alcohol he used as a base, a proprietary secret, allows a pint container of the concentrate to last about a year, making it less perishable than the other liquids on the market. It works much better than any of the powders.
A maximum of three cuttings are stuck into each plug, and the water level in the clear trays is kept to one inch (2.5 cm) deep. We have rigged a screen to spare the cuttings from hot afternoon sun. Other than keeping the water level steady, once the cuttings are stuck, we do not trouble them for six weeks, except to pull out cuttings that have shriveled. We use bottom heat, both electric mats and cables, at 70F.
After six weeks, we start tugging, and using a pointed chopstick to slide down the wall of the plug and lift the cuttings out. Below is a picture of two perfectly rooted cuttings of Clematis ‘Brewster’. Well-rooted cuttings like these should be moved on to a “weaning” medium immediately, as they aren’t getting any fertilizer from just the water and perlite. Any perlite attached to the roots from the plugs is left there undisturbed. The weaning medium is 50% perlite + 50% coconut hull fiber (syn. coir), and this is moistened. We plant the cuttings into 5″ deep band-bottom pots (2-3/8 inches square), and top this mix with 1/4 inch of number 2 grade chicken grit (number 1 is too fine). The pots are packed into deep flats and put back on the bottom heat. After the cuttings have had a week to recover from this transition, we begin giving them 1/3 strength fish fertilizer (5-1-1) to encourage top growth. They get 1/3 strength fish fertilizer once a week until top growth is vigorously emerging.
When the roots have filled this size pot, they will move into #1 (syn. 1-gallon) plastic pots, and hopefully new leaves and shoots are developing along with the roots. Once in these “finishing” pots, the clematis are removed from bottom heat. They will be ready to plant or sell in another year. We will sell no clematis before its time!
FRCC offers a propagation class every summer, usually in late July, which we have found to be the optimal time to take cuttings for many types of clematis. If you volunteer at the collection, you may be pressed into service as a clematis propagation assistant at any time! At the advice of nurseryman Bob Gutmann, we will be taking cuttings from the New Zealand hybrid evergreen clematis (such as C. x cartmanii ‘Sweet Hart’) in another month (mid-November). We’ll post more pictures then!
The American species in the clematis Viornae Group are pollinated by hummingbirds. These New World birds, with their long bills and tongues, have no trouble piercing the dense plug of pollen-bearing stamens (and pistols) that jam the opening of the urn-shaped blooms like those of the seedling pictured here. They easily reach the nectary chamber at the base of the filaments, and indeed, a pair of Anna’s Hummingbirds hang around the test plot, feeding on the Viornae seedlings we are evaluating. As they feed, their beaks and foreheads are liberally dusted with pollen. At Luscher Farm we are blessed with healthy populations of European honeybees, but they are completely flummoxed by this group of clematis.
The bees seem to know there is nectar in these blossoms, but there isn’t room for them to crawl up into the flower—the bees are too big, and the stamens too tightly packed. Undaunted, the bees attempted to separate the seams between the sepals, using forelegs and mouth parts to try to pry an opening to access the nectar. I watched their efforts for about 10 minutes before realizing I should be taking pictures! During the time I observed the honeybees, I didn’t see any of them succeed in opening the sepal edges, and was surprised that the bees would expend so much energy trying. A couple of rows away, native bumblebees were feasting on a Clematis macropetala seedling’s flowers (the same plant that Killdeer’s nested under a year ago), an open bell much easier to navigate in, and a flower not exploited by the hummingbirds.
Why would so many non-native bees be trying so hard to crack these clematis blooms? I did detect a slight fragrance, but there are many easier plants to drink from nearby. If these bees are ever successful at opening clematis in this nontraditional way, I’ll let you know.
