Yuccas, Roses, Lilacs, Maples, Plant ID & Rain Barrel

Cleaning up rabbit-chewed yuccas; what to spray on rose bushes this year; pruning lilacs; how to keep a small maple tree, small; possible identification of a noxious weed; and how to keep the water in a rain barrel ‘sweet’!
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 15, 2008

Above, a shot of Greg DeGreef’s mystery plant growing in Edmonton. I think it may be Japanese knotweed. Below, actual shot of the flowers of Japanese knotweed, courtesy the USDA.

At least one identification problem this week. But, let’s start with this from Shirley Feaver received a way back on May 31. “I have [outdoor Yuccas] in the garden and the rabbits have almost destroyed them. How can I clean them up? The main stem is okay but the leaves (fronds) are really tattered. Any suggestions?”

My only suggestion is to fertilize the plants much more heavily than usual with an all-purpose 20-20-20 soluble fertilizer--perhaps every two weeks until early August. That should prompt them to put on extra growth this summer. If the rabbits remain active, simply put some wire, or even nylon mesh in a circle around the plants. Good Luck!

Then on June 8th, Tom and Lynda Kennedy wrote: “First of all love to hear all your very informative comments. Still can't quite figure out where to prune the lilac trees, my husband and I heard about cutting the wrong end off and I think we cut off next years growth, but I am going to get better informed on that one.

But my question is about roses. We used to use Floritect and found it to be wonderful for all the little critters that ate the leaves of our roses and it also helped with the yellow leaves. Since we can no longer buy it on the shelf anywhere, can you suggest a good replacement for our roses? This year we look like we are going to have a bumper crop and would hate to lose out on their beauty. Thanks and keep up the good work.”

It is (or soon will be) a whole new world as far as pesticides are concerned. Personally, if I was in Ontario I would be stocking up on good insecticides while you can still get them. Floritect--a combination insecticide/fungicide under the Wilson label should still be available. If you cannot find it in your favourite garden centre or garden supply store (be sure to check Humber Nurseries and Sheridan Nurseries), try calling the manufacturer, Sure-Gro at 1 800 268-2806.

Next year will be another story, but there is plenty of time to deal with that.

And, by the way, pruning of lilacs, at this time of year, is reasonably simple. Just be sure to cut off only the old flower heads, and not any of the new growths or growth buds that are emerging immediately below those old flower heads.

On June 8th, May Daemi wrote from somewhere in southern Ontario with a general type of question: “We have a dwarf maple tree in the back yard but it seems to be growing taller every year. If there is any way that we can at least have it trimmed so it'll stay the same size, it would be helpful. Thank you in advance,”

Unfortunately May did advise me the type of maple tree she has. There are major differences. However, regardless of what it is, if she either prunes it herself, or has a commercial tree firm (such as the Bruce Tree Expert Company--416-252-8769) do it annually, it will be fairly easy to keep it confined. I cannot offer much more without specifically knowing what tree she has.

Then on June 12, Greg DeGreef from the University of Alberta in Edmonton, wrote to Donna Dawson about a plant I had not seen before; “Can you tell me what this plant in the attached photo is? This is a large grove in front of a friend's house, he gave me a couple of root pieces and it is doing very well in front of my house. It is perennial and I was told it was bamboo, but my research so far tells me that most bamboo has pointed leaves. The shoots are purple in colour. Thanks.”

Donna said she didn’t think it a bamboo either (not many grow in the Alberta climate), and when I looked at the photo I thought it might by a plant known as Japanese knotweed (Polygonum cuspidatum). The distinguishing feature would be the tiny white flowers displayed during the summer. I’ve attached a USDA shot of them. If it is not Japanese knotweed, I would still think it is a Polygonum, just not sure which one. Do check the flowers when it blooms, and let us know.

By the way, the USDA says it is a noxious weed over much of the U.S. and Canada except (in Canada) it is not known in Alberta and Saskatchewan. But as to hardiness, it is known in Alaska, so it should be hardy in Edmonton.

And finally this week, Roxy W. of Beamsville, who sometimes participates in our chat session on Sundays (now in hiatus for the summer), wrote on June 11th: “Hope all is well! I have a quick question for you: Do you know of any product or home remedy to prevent the water in my new rain barrel from turning smelly? It has a sulfur smell. With all the rain we've had, I haven't been able to use a significant amount before it gets replenished with the next rain. When I watered tonight I noticed the smell for the first time. I've searched the net and found a few suggestions but I'm not sure which to try: add a cup of bleach or vinegar (don't want to take the chance of killing any plants so I think I'll steer clear of those), hang a copper pipe in the water, or a bag of charcoal. Have you heard of or tried any of these remedies or have one of your own you'd like to share? Thanks in advance Art. Happy Gardening!

“P.S. Still waiting for the elusive Red Caroline Delphinium. I check regularly with Mori Nurseries...they said not to give up hope!”

This was my brief response: “There really should not be any trouble with adding bleach to your water because by the time you come to use it, the javel component will have long evaporated. Adding charcoal should also work—it is used to filter and clean some ponds of algae etc. The copper pipe sounds interesting, as that will likely acidify the water, and slime/algae does not like acid conditions and tends to die. That’s an old pond trick as well.

“I guess as long as the Mori people are optimistic you should be too. I wonder from whom they are buying it. Obviously they haven’t grown it themselves, or you would think it should be ready now. Did you join the Delphinium Society yet?”

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