New Clematis & Questions

A new Clematis, and an unusual vine and questions about problems with green ash and Japanese maples, as well as transplanting plants as diverse as Dendrobium orchids and rhubarb!
by Art Drysdale
by Art Drysdale


Art Drysdale, a life-long resident of Toronto and a horticulturist well known all across Canada, is now a resident of Parksville, British Columbia on Vancouver Island, just north of Nanaimo. He has reno-vated an old home and has a new garden there. His radio gardening vignettes are heard in south-western Ontario over radio station Easy 101 FM out of Tillsonburg at 2 PM weekdays.

Art also has his own website at

June 25, 2006

Above: Clematis Avant-Garde™, and flowers of the corkscrew vine, both as illustrated by the Park Seed Company.

Park Seeds of Greenwood, South Carolina is introducing a brilliant new Clematis this year from master Cle-metarian (their word!) and friend, Raymond J. Evison. They describe it as a “flamboyant semi-double Clematis in a rare colour combination of rosy magenta outer petals surrounding a central puff of lavender-pink stamens. Most Clematis bloom in spring to early summer, but Avant-Garde™ extends the season of colour with loads of distinctive two-inch blooms from mid- to late summer into fall. Extremely free flowering and resistant to wilt, this vigorous woody vine grows three metres (10’) tall and about a metre (3 – 4’) wide, perfect for any size garden.”

Unfortunately, Park does not ship plants to Canada, but no doubt garden centres here will have it available next year, if some don’t already have it. Park is charging $9.95 per plant in a 2½” pot.

While writing about my long-time friends at Park Seed (has anyone encountered Dave Phillips recently?), I should also mention the corkscrew vine (Vigna caracalla). Here is what they say about it. “With a powerful, sweet fragrance that may remind you of hyacinths, fragrant corkscrew vine is the most exciting climber to come along in many, many years. All it asks is plenty of sunshine to bloom steadily from midsummer until well into fall, turning your patio, entryway, or even the humble mailbox into a perfumed paradise!

“The blooms are simply exquisite, shot with primrose and shell-pink tones against a silvery base. They are shaped something like a nautilus shell, with a thick, coiled centre and delicately curved outer petals. Each 3-5 cm (1¼ - 2”) blossom is distinctively beautiful--and you'll get masses of them over the bloomtime of this 6-7 metre (20-25’) vine! Starting in midsummer (when the serious heat arrives!), they arise in 30 cm-long bunches up and down the stem, dangling enticingly from arbors or large hanging baskets! The foliage is lovely too--15 cm long, with three ‘fingers’ and a soft, downy texture.”

* * *

Marilyn Daniell, of south Pickering, wrote last Sunday, as follows: “I have a question regarding three green ash trees--approximately ten years old. This year there is very little new growth or leaves on the trees from the middle of the trees down. All the new growth is at the top of the trees. I have been told that the problem is lack of water and I should let the hose drip on the trees for 2 -3 hours at a time. Perhaps I should mention that I have clay soil. I am quite willing to water if this would appear to be the problem but I am wondering if the lack of foliage is due to lack of water or is there another problem that watering is not going to solve. I am wondering if the trees will rejuvenate or if new growth will only occur at the top of the trees and I should address this situation now rather than let the trees get taller with no new growth on two thirds of the tree. Your advice would be much appreciated.”

The specific cause of the trees’ growth only occurring at the tops could be attributable to more than one cause. For example, if the trees are growing in a shaded area, that would make them reach up (much the same as in a forest) and most of the growth would then be at the tops. I don’t personally see the lack of water causing the problem you describe. I am checking further and may be able to advise more shortly.

Faye Bourgeois, also from AM740’s southern Ontario listening area, wrote again a few days ago: “Once again I'm looking for information. I got a Dendrobium orchid at Christmas time with miniature flowers. It had a long spike and a lovely cluster. My question is, will this same plant flower again, or do they only flower once? A new plant is growing and I'm sure it will flower eventually. If the other plant will not flower again, should I remove it from the pot? There are no new leaves coming on it. Hope to hear from you, and many thanks in advance.”

Faye, your orchid will definitely bloom again. The new shoot is produced from a new pseudobulb but it is not likely sufficiently mature to separate from the main plant. And, I wouldn’t think you need to re-pot the plant since you just got it last Christmas. The best time to re-pot it will be after it blooms, but certainly not yet. Be sure you keep fertilizing it with an orchid fertilizer at weak strength.

Dave Thien from nearby Nanaimo wrote with a question about rhubarb, something about which we hear little, and yet it makes (I think) a delicious dessert. My response is a general one that applies all across the country. Here’s the question: “My Mother-in-law wants to transplant some of her rhubarb plants, is this time of year okay or should she wait until the fall? The roots of one of the plants is at the surface and these plants have been in their current spot for at least ten years if not more and are still producing good shoots. How deep should I dig so that I don't harm the roots much? Thank you in advance.”

The ideal time to re-locate rhubarb is late winter or early spring. Depending on your location in Canada, I would leave it until then. This question illustrates the need for those asking questions to include their area/city.

In digging the clump(s) care should be taken, but once the clumps are out, it will be fairly simple to break them apart and divide. Keep only the best tubers and discard the rest. Plant at the same depth, preferably at a new site with similar conditions.

Finally this week, John Harrop, possibly from the Hamilton Mountain area in southern Ontario wrote with another tree question: “I have a Japanese maple which for some reason has no leaves on its top. The lower branches are fine. Should I cut off the non-leafing top and branches?”

What to do depends on the condition of the branches which are not leafing. If the bare branches are still alive (a simple thumb-nail scratch of the bark will reveal that--green and slightly moist indicates a live branch; brown and dry means that particular part of the branch is dead. I would not cut off live branches, but certainly do remove all dead growth. If there is dead growth, then the question is what caused the death. Again here, your location could affect the answer. In any case, Japanese maples do die of verticillium wilt (Verticillium albo-atrum), sometimes over a period of years, and sometimes quickly. There is always a distinguishable olive-green colouration in a circular pattern within the sapwood (just under the bark) when this is the problem. A good clean cut with secateurs should reveal this easily. Something else that seems to be hitting maples recently is a leaf spot known as Cristulariella depraedens. Some control of this may be possible with a copper fungicide generally available at garden centres. With these diseases it is important to rake up all the leaves that fall, at any time, and place them in the garbage, not the compost.

If cutting out dead branches that seem to be affected by the wilt, it is important to remove at least 20 cm of growth further down the tree (branch) which is still alive if you are to arrest the disease. And, be sure to put out the cut section in the garbage.

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