Plant Hardiness & New Carrot/Flower

Who is kidding whom about certain tree hardiness; getting rid of Pampas grass, and a new carrot you’ll grow as a flower!
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

November 30, 2008

Above, a field of Sheridan Nurseries hardy shrubs growing at Glen Williams, Ontario in the late 60s; author photo. Below, the new ‘Black Knight’ carrot with its lovely flowers that many floral arrangers will covet!

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. On November 22nd, 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.” It is still on the site.

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 re-ports from various other growing nurseries in those areas.

When Lawrence C. Sherk and Arthur R. Buckley (both of the then Ornamental Plant Section, Plant Re-search 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 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 (also currently on the site). 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.

* * *

Well, it’s the season of the seed catalogues. I have already received the wonderful Stokes Seed catalogue from the folks in St. Catharines, Ontario and no doubt over the next few weeks, many others will roll in as well.

Just as I was writing this item on Friday, I noted an e-mail from Johnny’s Selected Seeds of Winslow, Maine that describes some of their new items. One ‘new’ flower in particular attracted my attention. It is a carrot! Now, most of you will know the white flower heads on the well-known wild carrot (Daucus carota), otherwise known as Queen Anne’s Lace (considered a noxious weed at least in Ontario). Well, our cultivated carrots produce a similar flower as well. But this new one, called ‘Black Knight’ (Daucus carota var. sativus), is definitely something different; as you’ll see from the photo (courtesy of Johnny’s) that accompanies this item. ‘Black Knight’ is actually an edible carrot, but it bolts [goes to flower and then seed] very early, making it a nice cut flower addition. Long, sturdy stems help to make it a great filler in floral arrangements. Its height is 105 - 120 cm (42 - 48”). The only drawback may be that it takes a little more than three months to come into flower from seeding into the ground. I guess you could start it from seed indoors, or buy transplants if they become available, but since carrots do not take well to transplanting, that may not be the answer either.

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