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Tree Roots & Houses plus Squirrels

Two different questions having to do with plant roots--can Dwarf Alberta Spruce be planted near a house foundation; and what to plant over and/or near a septic system; plus the Wollemi pine and what to do about squirrels!
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 7, 2009

Above, two shots of dwarf Alberta spruce in house foundation settings; and below, two shots of a young Garry oak and a close-up of the foliage; and the non-related silk tassel tree (Garrya elliptica); and two shots of the amazing Wollemi pine.
Author photos.

It seems I am still catching up on queries posed to Donna while she was away at Chelsea. Here is another from Karen, of unknown location: “Hi Donna, a friend of mine wants to plant a couple of Alberta spruce, but she wants to plant them next to her house. She has a basement and I would like to know if this is safe. I'm aware that tree roots can cause damage. If she can do this how far away should she plant them? Thank you.”

Alberta spruce, or dwarf Alberta spruce (Picea glauca ‘Conica’) are not large-growing trees and the roots should not be a danger for a foundation, as far as I am aware. However, it would be best to be sure that the tree(s) are planted out at least .5 metre (20”) from the wall. This gives the tree(s) a much better chance of success, and as well, it generally assures the plants will receive a reasonable amount of rain; i.e. always plant trees or shrubs out from foundations to be sure the plants will not be deprived of moisture by an overhanging roof.

The second question is from Mandy B. And she kindly told me where she lives. Here it is: “Hello, I live just north of Qualicum Beach, BC on Vancouver Island. Our property is half an acre and our septic field is pretty much smack in the middle of our lawn/yard. I dream of having a lush, colourful back yard full of various shrubs, trees and plants; what is safe to plant on/near a septic field and how far away should trees be planted? Is there anywhere on my property that I can plant a weeping willow?!?!”

Now, this is a more difficult ‘root’ problem! The best ‘ground cover’ for use on top of septic fields is grass or wild-flowers. Their roots generally will not interfere with the septic system. Many, perhaps I should say “most” shrubs and certainly all trees should be kept away from a septic field. The rule of thumb is to keep them a distance away from the closest section of the septic field by the equivalent to the ultimate height of the tree/shrub. Some trees with particularly aggressive root systems (weeping willows, poplars, many maples, beech, birch etc.) should be even further than that.

The reason for this is that the nutrients that are emitted from the septic field will be sought by actively growing tree roots which will then infiltrate the septic field causing it to fail, often in a short time. There are some trees which are generally considered to have less invasive root systems--including dogwoods, crabapples, ornamental cherries, pines, spruces and oaks (which have large root systems but are almost always much less invasive tap-rooted).

So, Mandy, I don’t know if you’ll be able to find a spot at least 45 metres (150 ft.) away from the septic field to plant your weeping willow! But just think how many nice oaks there are. You may even be able to grow a Garry oak (Quercus garryana) although that would be very unusual. Though they grow as far north on Vancouver Island as the Nanaimo area, I have not seen any north of Qualicum Beach, but I’m sure there are some. Nurseries do sell the trees, and you can even grow them from the acorns they produce.

The other nice aspect of having some Garry oaks is the associated ecosystems, particularly of wildflowers, that will be possible once you get a few Garry oaks established. Check out . Good Luck!

While writing about Garry oaks, I should also make mention of a completely unrelated species--the silk tassel tree (Garrya elliptica ‘James Roof’). While I have seen this growing in the Victoria area, I have not seen it up island al-though (again) I suspect it can be grown in the right conditions. It has male and female forms on separate plants, and the male forms have the longest and most elegant silk-like tassels in mid-winter and early spring!

The next question this week came from Henry Quon in Vancouver. He asks about the Wollemi pine: “I am interested in purchasing a specimen of this rare and very ancient plant. If I can't make it out to Parksville, is there any other way I can obtain one? I currently reside in Vancouver. About 2 years ago, I visited Drumheller, AB to see the Royal Tyrell dino museum because I have always had a life long interest and fascination with dinosaurs. This botanical find is probably the next best thing to finding a living dinosaur and is something that would make an excellent conversation piece.”

Depending on whether Henry has a car available to transport him, obtaining a Wollemi pine should not be difficult, particularly in Vancouver. Brian Minter’s Country Garden Store at 10015 Young Road North in Chilliwack has them at all times as far as I know. Other garden centres too handle them, and a phone call in advance of a visit is always appropriate!

Finally this week, Kathy Watson, of unknown location, wrote this: “Do you have any suggestions of how to get rid of squirrels that are digging up my new garden? I'd be grateful of some ideas.”

Since you haven’t told me from whence you write, I cannot be certain that any or all of the products that I would normally suggest for control of squirrels are available. The year-old pesticide law in Quebec and the recent new one in Ontario will likely mean that some of the products are no longer available. It will be worth your while to check various suppliers.

My favourite squirrel deterrent is the product Squirrel Away™ which is a powder designed to be mixed with bird seed. However, it can be used in other ways. My next recommendation would be a product called Ro-Pel followed by Havahart’s Critter Ridder. There are also ultrasonic electrical devices which I have used in the past (for raccoons)--they work by emitting a high-pitched ‘noise’ (usually unheard by the human ear) but I found they had to be used right at the start of the season, and then continually for the entire season.

You may encounter ‘flack’ about Squirrel Away, re it causing squirrels to harm themselves, but I am more than satisfied that that does not occur as documented by the manufacturer.

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