Dividing Perennials; Drying Leaves & Shade

Signs of when perennials need dividing; more questions about drying leaves on Japanese maples; what and how to plant in the shade (and roots) of a (Norway) maple tree; and about the possible ‘straightening’ of a thornless honey-locust tree.
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

May 27, 2007

Above: Three more shots from my garden, just this past week; these are all at the east end of our small pond, and the building is my office/studio. The Rhododendron is ‘Virginia Richards’, the bright red azalea is ‘Crimson Hino’ and the blue shrubby vine is Potato vine (Solanum jasminoides). Author photos. Below, Ruby McDonnell’s Skyline honeylocust.

Diane Powers from right here in Parksville has the first question today. She actually sent it on May 8, so you can tell I’m two weeks behind! “I have two big plants of Lamb's Ear, and they both have big craters in the middle with lots of dead material. I would like to know what I should do. Does this mean they should be split or decreased in size? Thank you very much again. I sure appreciate your good advice.”

The fast answer Diane is yes, they should definitely be split/divided. Here in Parksville with our still-cool temperatures, you might get away with doing it even now, but otherwise, I would wait until later this fall, or do it early next spring. In the east, while it could be still be done now as well, but due to the hot temperatures, the newly transplanted clumps would need to be shaded and especially cared for more so than here. This is not an uncommon happening--it happens with many perennials and dividing/splitting is generally best done with most herbaceous perennials about every three years, or as needed.

Just two days later, David Jakobi of Tillsonburg, Ontario wrote about maple keys: “How can I get rid of the un-wanted maple keys that are coming up everywhere in the lawn and garden? I have used landscape fabric and then mulch on top and they are still coming up this year. Thanks for any advice that you can give me.”

Maple trees are a nuisance with their samaras or keys. In the lawn they are not usually a problem as regular cutting will knock them down. In flower beds it is another story. If you used landscape fabric last year, and the keys have germinated this year it is likely you used a bio-degradable form of landscape fabric. Instead, you need one that does not bio-degrade and so will prevent the weeds coming up for several years. Keep in mind however, if you place mulch over the landscape fabric--that just provides a growing medium for newly fallen keys. Better to try covering the landscape fabric with large bark pellets or chunks, or stones.

Johanne Drolet of Milton, Ontario, wrote two weeks ago with this common problem: “I have several problems with my Japanese maple. It is facing north on the east side of my garden. I live in Milton. We had a very cold winter this past year. My tree was about 6 years old and was doing great about 5 feet tall. The past few years it had drying leaves on it in the summer months, and this spring I lost more then half of the branches because they were dead after the winter we had. I trimmed back the branches that were dead, it does not look too good but could I save this tree and what should I be doing to make it come back. I forgot to mention that I have another Japanese maple at about 30 feet away from this one and it is doing great. Will it get this disease that this one has? I love my garden and those Japanese maples. Could you please advise me on what to do with this situation? Thank you so much.”

To begin Johanne, I am not certain, from your description, that your tree has a disease. I have discussed diseases of Japanese maples (Acer palmatum) on numerous occasions on, likely the most recent being October 29/06 ( ). I have myself experienced Verticillium wilt (Verticillium alboatrum) both in Toronto, and here in my present garden in Parksville, B.C. That tell-tale olive-coloured ring just below the bark makes it relatively easy to see if that is what is causing the problem. Diagnosing the Cristulariella depraedens is not nearly as easily accomplished.

However, I believe your problem may just be the leaf scorch which precedes leaves on many branches drying up. The hot summers of late have made this a common occurrence. One of the answers to this, again, is the application of a soluble (liquid) fertilizer to the entire tree on a regular basis (every two or three weeks), using, likely, a hose-end sprayer. The other important point is to keep the soil (turf or otherwise) around the base of the tree from drying out during the summer months. As to the fact that the other tree is not affected, that could simply be that it has a better established root system, and/or is slightly more shaded (the tree and the surrounding soil).

Robert Ireland, a retired radio/TV personality wrote on May 17th, “I just realized from "ICanGarden" that you have moved from Ontario to Vancouver Island. I too lived in Victoria for a year back in the early sixties when I worked for the local TV station there. I catch you occasionally on AM 740.

“My question is I have a flower bed that gets morning sun and is shaded by a big maple tree on my neighbor's prop-erty. As you can probably guess, the soil is hard to till as there are all sorts of root branches from the tree. Consequently many flowers do not do well in that location. Can you tell me what sort of plants with shallow root systems can be put there? Or should I just sod it over and forget it.”

The answer to Bob’s question could go in one of two directions. The first would be to plant shade-loving annuals such as Begonia, Browallia, Sweet Alyssum, Coleus, Impatiens, Monkey flower, Spider plant and German ivy. Second, if the mass of roots is the main problem (which it will be if the tree is a Norway maple [Acer platanoides]) then you may be better off to remove the grass, and put in some gravel, on which you can then place some fairly large, heavy containers in which you plant these and other shade-loving annuals.

Finally this week, Ruby McDonnell from somewhere in southern Ontario wrote on May 22nd, “I tried to get through to your radio show on AM740 last Saturday but unfortunately was not successful! I would appreciate your advice on a Skyline Honeylocust which was planted on July 29, 2005. It is a very young tree even though it is approx. 12' tall. The circumference of the trunk is approx. 4 inches and it curves in and out in a couple of places. When we planted it, we staked the tree and pulled the trunk to try and straighten it. We have taken the stakes away now as we think they should only be used for two years but the trunk is still not straight. My question is – should we stake it up for another year or do you think the trunk will straighten by itself over the next few years? I have attached a photograph of the tree. A response would be very much appreciated and I thank you in advance.”

Ruby, generally trees are not staked to try and straighten their trunk; and in fact that is very difficult to do. I would neither stake the tree again, nor worry about it not being straight in stature. My old friend the late Tommy Thompson, when he was Commissioner of the Metro Toronto Parks Department, used to spend about a day a year going around the nursery where I worked and he was not only looking to see the size and variety we had (and hence what was suited to his parks), but he was also searching out trees that had “character”. Your tree would definitely have been chosen by Tommy because it has character.

Don’t worry about it, your tree should develop well, and you’ll come to love its character!


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