Some varied questions that came in over a decade ago
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

April 8, 2018

Above, In answer to the last question: two shots of Leyland cypress, potted and then recently planted. Below, Cherry laurel (Prunus laurocerasus) seen here growing in East York in southern Ontario where it is considered NOT to be hardy [though there are some interior green leaves!], although it is hardy in the milder areas of British Columbia.
Author photos.




Some varied and interesting questions this week. I’ll start with one from a new gardener, Hedda Knott of Tillsonburg Ontario. “I am new to gardening and surfing the web. Please direct me to someone that could help me with my Magnolia tree. I do believe it is a saucer magnolia. There are several branches that have split bark from 1 to 2 feet long. The bark seems to have lifted away from the (pulp?) and I think that the bark will eventually just peel away entirely besides leaving gaping rips into which insects and disease can enter. I would like to save the tree as it must be 12 or more years old. Thank you for your help. Love your radio program.”

Tree problems are often difficult to diagnose, and for that reason, I generally recommend that if the tree is important to your garden, and/or to you, that a certified ISA (International Society of Arboriculture) arborist be called. In Hedda’s case, the split or torn bark may just be some form of physical damage, and provided it is just a strip up and down each branch, it can easily be repaired. All loose bark should be removed with a sharp knife and the stripped area should be boat-shaped (pointed) at each end. This will encourage the bark to heal over the stripped area eventually. There is no need to coat the exposed sapwood (pulp as Hedda calls it) with a tree wound dressing as used to be the recommendation. If you wish to cover the exposed area, just use a white latex paint.

The only time when stripped bark becomes a major problem is when it is removed all around the entire circumference of the trunk, or any particular branch. That almost always spells doom for the tree (if it the trunk affected) or the particular branch so affected.

June White, of Goderich Ontario wrote with what she thought was some good advice, but which actually is not! Here is her note: “Two or three Saturdays ago the question arose as to how to eliminate worms in onions and carrots. I never had a problem with carrots, but indeed the onions and radishes seemed to be good fare for the worms. Someone told me to sprinkle salt (table salt) in the row before planting radishes or in small dents made in the ground before the onions went in. The result NO MORE WORMS. Have a good day.”

I am afraid I could not disagree more with this recommendation. Anytime salt (table or otherwise) is placed in a garden one is asking for trouble. Sodium chloride (NaCl) is a much stronger poison than any of the pesticides that have recently been banned from the Canadian marketplace.

You may know that most granular fertilizers (and most soluble as well) are actually salts; that is why the granular ones work well to melt ice from sidewalks and driveways in winter. Too much fertilizer on any plant causes a build-up of salt in the soil and will quickly kill the plant(s). When I get telephone calls about indoor plants, such as African violets that appear to be dying, I know the answer is either to repot the plant, or flush the soil heavily with water for an extended period of time to wash out the salts. Likewise, when someone calls and says they spilled fertilizer on their lawn, and the lawn turned brown in the entire area I know it is a case of too much salt. Again, it has to be flushed through and eventually ends up in underground aquifers. Not a good prospect. Sorry! And, thanks.

Paul Lokash of Toronto wrote recently: “I have bought a 10 acre property outside Toronto and inherited 3 lovely flower gardens, mostly different wild flowers. Unfortunately all have large, tall growths of grass in them. The only way I have been able to deal with it is to pull the grass out by hand, but it continues to grow back. Do you have suggestions?”

My suggestion here is short and simple to say, but will take Paul some time to carry out. I would advise him to buy a container of Roundup concentrate (not the Ready-to-spray and not the Ready-to-use forms), and mix it in a fairly large plastic container with a full-size opening at the top (peanut butter jar for example). I would also double the suggested mixing ratio (twice the amount of product to the amount of water) and then get an old paint brush and paint the solution on all parts of the grass, at the same time being extremely careful not to get any solution on the flowers he wishes to keep. If it happens that some of the product accidentally gets applied or splashed onto his plants, it is a simple matter to pull off the affected leaves.

The Roundup will kill only the plants whose leaves you coat, and the killing action will extend to the tip of the root. There are only a few plants on which Roundup is not effective: Horsetail (Equisetum), Goutweed (Aegopodium podagraria ‘Variegata’ and Canada thistle (Cirsium arvense).

Deborah Sheppard, also from Ontario wrote: “Love your show--very informative. If you get a chance to respond; I am a good gardener but my lawn looks scraggly. I have checked and there are no bugs. I try, I try--I fertilize as directed, I reseed, I water properly, I mow carefully at the right heights. I recently tried Scotts Turf Builder with the spreader as directed and my lawn is burned in several large patches--it's not supposed to do that. Suggestions? Thanks!”

Well Deborah, it’s hard to believe that any modern fertilizer would burn in the spring season, unless it was piled on the lawn and the granules smothered the turf! The ‘burning’ is more likely from another cause--chinch bugs or other soil pests/grubs, or a salt build-up such as I’ve just described above. It could also be that you have a mixture of non-compatible grasses in your lawn, which may include one of the bentgrasses. Since the cutting height for most grasses is not suitable for bentgrass, it tends to grow “sideways” and takes on a yellow colour. If that is the problem, you’ll have to kill off the bent using three or four applications (once a week at least) of a 2,4-D/Mecoprop/Dicamba product (such as Killex or WeedOut).

Or you can use spot treatments of Roundup, and a few days later, re-seed the dead spots; but I wouldn’t try that until late August.

Sheila Lenes of Calgary wrote a couple of weeks ago with an unusual problem: “Art, We have an industrial strength composting toilet and currently have a fly infestation. The company, Phoenix Composting Toilets, has recommended that we use an organic pesticide--Pyrethrum. Does Doktor Doom--Residual Insecticidal Spray have this compound and is it going to work? Thanks.”

Doktor Doom’s Residual Insecticidal Spray is the product I would use because its effectiveness will last at least two months. It is a Permethrin product which is actually a chemical copy of the naturally-occurring Pyrethrum. It is quite safe, and does not bare a poison symbol on the aerosol spray cans; but if you wish to stick to the organic Pyrethrum, Doktor Doom has that as well, under the name Botanics.

William Bissett, in Dundas Ontario wrote with a familiar question: “I have a very tall (approx 40') Walnut tree in my yard. It is so tall the underneath of the tree is quite sunny, and I would like to plant some kind of flower garden underneath the tree, but understand that Walnuts release a toxin that can be deadly to some (all) flow-ers/shrubs within the drip circle. Every couple of years, the lawn underneath the tree is killed off and I'd like to put something (a flower/perennial garden) in that area that is more tolerant of the Walnut tree. Any suggestions? I Listen to your show on AM 740, and find it very interesting and informative.”

First, what you have heard is generally correct. However, most of our common grasses (bluegrass for instance) is tolerant of the juglone toxin, so a lawn should do well if it has reasonable sun. As to flowers, there is quite a long list of perennials that tolerate juglone as well. For example, in perennials you could choose from daffodils, dog tooth violets and primulas (the latter will prefer some shade) for spring effect; and hostas (they should do well in that location), heucheras, Iris and lilies for spring, summer and fall. Periwinkle (Vinca minor) will grow well if you want an alternate groundcover, and shrubs such as Forsythia, lilacs, dwarf burning bush (Euonymus alatus), honeysuckles, mock-orange and Viburnum perform well. I trust that is a sufficient list.

The D. J. Vanderkooi family, from somewhere in British Columbia wrote as follows: “We have recently built a house on acreage that is often frequented by deer. Our house faces a fairly busy road and for privacy we would like to plant a fast growing, deer resistant hedge. We've heard that deer don't like Western Red cedars. Is this true? What would you recommend? Thank you.”

My response was as follows: “You didn’t say in what area you are living/gardening, but I assume it is the lower mainland or on Vancouver Island.

“You are correct that deer generally do NOT attack (eat) western red cedar (Thuja plicata); however, unless you have a great space, they generally should not be planted as a hedge. They can be pruned annually to keep them in bounds, but given a couple of years with no pruning they will take off for the sky. The ultimate height can easily be 60 metres or 180 feet!

v“If you have the space, they may be your answer.

“Another possibility is the Leyland cypress (Cupressocyparis leylandii) which grows even faster than the western red cedar, but not nearly as tall. Its maximum height is usually considered to be 16 – 20 metres (50 – 60 feet). It can easily achieve a metre of growth in the second and subsequent years. Some people do not like these because they are subject to a couple of diseases, particularly Coryneum canker which is more prevalent in severely trimmed trees (i.e. hedges).

v“A couple of the plants I would consider are cherry laurel (Prunus laurocerasus) which many people detest as a hedge because of its “rampant’ growth, and Portugal laurel (Prunus lusitanica) which is slower growing and tidier. I personally like the cherry laurel for a tall hedge, so do consider it. 


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