You see them everywhere. They hit the popularity charts about 10 or so years ago as homeowners set their sights on tall narrow trees for screening in the residential garden. The Swedish Columnar Aspen is an excellent screening tree for privacy or as a sole specimen because they are so tall and narrow, taking little room in the garden visually while providing for the homeowners or commercial management's desires for treescaping. (think of the Cypress in Italy to visualize the form)
Here are a few particulars about this columnar aspen:
Name: Populus tremula (Swedish Columnar Aspen)
Zone rating: 2 (Canada)
Height: 30-45 feet at maturity (9.1--14 m tall)
Width: 5-8 feet wide (1.5--2.4 m)
Fast growing: interpret as more than 1 foot per year
Description: A nice columnar tree with a dense canopy. Excellent wind break or screen for privacy. Leaves are green on both sides and have somewhat wavy edges. Tend to branch near to the ground. All trees sold are male so they will not produce the fluff to which so many are allergic. Note: Lois Hole's book, Favorite Trees and Shrubs, states it "can be planted next to a house as its smaller shallow roots are not invasive." (page 85)
That was the love part...
now for the hate.....
A few years ago my next door neighbour planted Swedish Columnar Aspen (populus tremula) near his fence, between our properties and that of his and his other neighbour's yards. These saplings were maybe 5-6 feet tall and you could only see the tips over the fence. At that time I was working at the garden centre and the staff were in discussions with horticulturists to determine just how suitable the Swedish Columnar Aspens were for foundation plantings. One or more horticulturists had the idea that these are fine to plant, even next to a house, because their roots are supposedly non-invasive. The Alberta Tree Nursery (a government funded agriculture and tree research site), however, disagreed citing 'they are members of the poplar family'. They would not recommend planting them anywhere near buildings. All of us in the nursery/greenhouse business have heard of the damage poplars can cause to sewers and foundations. But these were different, or so we thought. So, it was unclear then....................
Now, perhaps 8 years later, these same trees have nearly reached their mature height of 30 feet (maturity can range between 30-45 feet) and I must admit I like the appearance of them. They are tall and narrow and the sound of their leaves rustling in the slightest breeze is soothing to hear.
PROBLEM......Those roots are not non-invasive! They have meandered over to our property, with shoots sprouting up in the lawn and next to the foundation of our house (some 15 feet away). Needless to say, I am not terribly impressed. Now, logically it makes sense that the roots would spread outward as they must anchor the tree in place. The Swedish Columnar Aspen does not have tap roots, therefore, lateral roots are necessary to retrieve nutrients and to act as anchors.
If you were to look over the neighbour's fence, you could see several more shoots coming up in their
poorly maintained lawn. So, one tends to rethink the non-invasive label -- does one classify the roots as non-invasive only if they don't enter the sewer lines? All the lines are in the front of the houses in our subdivision so that is not a concern. The foundation is a major concern, though. Based on the evidence I have witnessed first hand, I would not consider these non-invasive!
Has anyone else had experiences like this with Swedish Columnar Aspen? Would you still plant Swedish Columnar Aspen in your garden, or as a foundation plant, after seeing this? I suggest the ideal location to plant this tree would be on the back perimeter of the property where roots cannot interfere with foundations or lines. Yes, I would. It's the whole love/hate thing.
If a Swedish Columnar Aspen is planted in a parking lot, surrounded by concrete, is it then non-invasive? I'm just asking..... (tongue in cheek)