False gardening advice gleaned from the Web; and sugar maples and Catalpas growing in Winnipeg—I don’t think so
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

December 18, 2016

Above, a Catalpa speciosa not considered hardy in colder zones than 5b, certainly not in zone 3a. Below, Sugar maples are similarly not hardy in zones colder than zone 4. Author photos.




A few weeks back I had to go to the Web to search for something fast, and happened across a site called Vitality Gardening, a part of Vitality Television, wherein the ‘expert’ appears to be Caroline Chartrand. On that Sunday, I made a note of one item that caught my eye: she was recommending planting a marigold plant in between each tomato plant so the marigolds would attract the insects to pollinate the tomato plants. Wow!

Now I have heard so-called organic gardeners recommending the planting of marigolds amongst vegetables before, but solely to prevent attacks by certain insects. Of course, when they make such recommendations, they absolutely never cite the evidence published by such as scientists and professors at the University of Guelph who long ago proved that the marigolds had absolutely no effect on whether or not the vegetables were attacked by insects. Now, there is some evidence that soil-borne insects such as deleterious nematodes (as opposed to positive nematodes sold to help eliminate insects such as black vine root weevil from rhododendrons or Japanese yews) can be controlled by the excessive planting of such plants as marigolds in the infected soil. But it certainly doesn’t happen overnight, or even over a season.

But to say to use marigolds to attract pollinating bees, that is a real stretch! First and foremost, I have never had it really demonstrated that tomato plants need anything to attract bees (or other insects) for pollination. In fact, they are often wind-pollinated. A quick check with some of those ardent balcony gardeners who grow tomato plants up as high as 20 or 30 stories in the air in Toronto will demonstrate that.

If one goes to the site mentioned, one finds a number of shaky and questionable recommendations and suggestions, particularly having to do with hardiness--far too many to mention here.

So, as with everything we see, read and hear now, especially on the Web, one must be careful to follow the various cable news services policies: all stories have to be verified by two reputable sources!

* * *

Periodically I like to check the Forum on this site to see the kind of questions folks are asking, as well as some of the answers (or rather responses!) that are provided. Some time back I noted Vic from zone 3a writing: “I would like to acquire some sugar maple seeds to start seedlings in late winter. I can share some catalpa seed in return if interested. Thank you.”

Well, I have a question for Vic. Does he intend to grow these seeds of sugar maple, and then plant them out in zone 3a? If he does, there is very little likelihood the plants will survive without significant winter protection. Sugar maple (Acer saccharum) is a zone 4 plant and ordinarily does not survive in colder areas.

Similarly, Vic offers Catalpa seed--does that mean he is growing Catalpa (possibly Northern Catalpa/Catalpa speciosa) in his zone 3a (e.g. Edmonton, Alberta or Winnipeg, Manitoba) garden? I don’t think so. It is a zone 5b plant (hardy in Montréal, P.Q. and St. John’s Newfoundland). For all practical purposes, the only other Catalpa is the much lower growing Umbrella (Catalpa bignonioides ‘Nana’) and it is basically the same hardiness--zone 5b.

My information source for all of this goes back about 42 years as the Canadian Plant Hardiness Zone Map and associated publications were being prepared for printing by then Agriculture Canada. I was chief horticulturist at Sheridan Nurseries in southern Ontario, and we had decided a year or two earlier to test out just how hardy some of the trees that we grew and sold were in various cities across Canada. We did this by supplying a number of trees including several maples, lindens, ash and oaks to various parks department officials we knew in large cities such as Winnipeg, Edmonton, Calgary etc. We also had reports from various other growing nurseries in those areas.

When Lawrence C. Sherk and Arthur R. Buckley (both of the then Ornamental Plant Section, Plant Research Institute, Agriculture Canada) and I met in Ottawa’s K.W. Neatby building to assign the highest zone numbers to almost all of the shrubs and trees listed in our Sheridan Nurseries catalogues (wholesale and retail) we each commented on our knowledge of where we had seen each particular plant surviving well. We consulted numerous current references as well.

Though some changes have been made in the interim years, basically the zones for most trees and shrubs remain the same even today. Hence, my dubious reaction to Vic’s indication that he is growing Catalpa trees and plans to grow Sugar maples in zone 3a.

All of the foregoing about the original 1967 hardiness zone map omits any mention of the newer 2001 version of the Canadian Plant Hardiness Zone Map. A much earlier article I wrote about the map in 2001, soon after attending its unveiling in Ottawa (along with Lawrence C. Sherk the Ottawa horticulturist for the 1967 version), appears on this site at: . I have also written two commentaries about the new map and they can be found at:  and .

It would be interesting to hear from Vic in the future.

Having spent so much space on Vic’s question which came from the Forum on this site, I should perhaps make a comment about the question about Pampas grass. The question comes from Penelope Caley who lives in zone 6b. Actually, it somewhat surprises me that Pampas grass (Cortaderia selloana) is doing so well in what is likely the Golden Horseshoe area of southern Ontario. In most ‘circles’ Pampas is considered a tender perennial, and many nurseries/garden centres do not even guarantee the plant over the winter due to that factor.

Although there is one suggestion about digging it out, I did not see any recommendation about trying Roundup on the established plant. My recommendation would be to cut the entire clump down to as close to ground level as possible in the spring, and when the new shoots are about 15 cm (6”) high, spray or paint them with double- or triple-strength Roundup. It might even be necessary to do such treatment two or three times to get a reasonable kill, but I do think it is possible for the product have an effect in this way.


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