By Jim Hole
The trend towards smaller yards, quite literally, narrows the choice of trees that perform well in small spaces. And if you have a skinny house, ipso facto, you will also have a skinny yard. So if you want to grow a tree or two, that means you shouldn’t transplant trees that will become sprawling giants.
The good news is that bigger doesn’t mean better when it comes to trees, and some of the very best varieties have a smaller stature without sacrificing any beauty.
A bit of science
So, why are some trees much smaller compared to their much larger cousins? Harsh environments are one reason. Hike to the higher elevations in Jasper or Banff and you’ll see dwarf evergreens that are a fraction of the size of the same species growing at lower altitudes thanks to the short growing season, poor soil, and cool temperatures.
But there are also many variants of otherwise large tree species that are naturally dwarf and will not grow too tall or too wide, even in an optimum growing environment. The reason these plants are dwarf is primarily due to a deficiency of specific plant hormones. A group of plant hormones called gibberellins are responsible for elongation of shoots and branches in most plants, but trees are often deficient in gibberellins so they remain relatively small compared to their larger cousins.
Plant breeders are constantly on the lookout for dwarf trees to select and use in their breeding programs. And given the increasing number of ‘postage stamp’ yards that we see today, there is an increasing demand for smaller trees and shrubs
What should you do?
The first thing to do is transplant trees that you like! This sounds simple, but I can’t believe how many times people tell me that they transplanted trees into their yards that they really don’t like. Spend some time doing a bit of research and consult with garden centre professionals before buying any tree.
Keep in mind that dwarf trees still grow. Even though they are classified as dwarf, they still require space to reach their full potential. Therefore, it’s important that you always choose dwarf tree and shrub varieties that fit nicely into your yard and that won’t outgrow their allotted space at maturity.
Also ensure that the dwarf plants are hardy. For example, I commonly see a dwarf spruce called ‘Dwarf Alberta Spruce’ being planted in our region. It’s a beautiful spruce, but ironically it is not hardy in Alberta. It suffers tremendously from winter drying and needle drop, and typically struggles for a few years before dying outright.
If want to plant some dwarfs, here is a shortlist of some great performers for our region:
‘Dakota Pinnacle’ Birch: A columnar birch that is tough and grows quickly and provides a nice privacy screen. It tends to maintain its leaves over winter, adding some additional privacy outside of the growing season
‘Purple Spire’ Flowering Crabapple: Grows to about five metres tall and just over a metre wide. Purple leaves and pink flowers really enhance this crabapple’s ornamental value.
‘Regal Prince’ Oak: This columnar oak grows about eight metres tall but is only about two-and-a-half metres wide. It produces leaves that are rich green on top and silver on the bottom.
Finally, never transplant a “cute” tree in your yard without understanding its true personality. An innocent-looking white spruce seedling will eventually grow into a 20-metre-tall, wide-spreading giant. There will be a dwarfing effect, but it will be due to the illusion that your yard is gradually shrinking as the spruce continues to grow.
Originally published by the Edmonton Journal, May 30, 2019