Included are native plants and introduced plants from other places that thrive here. Woody plants are becoming a challenge to Calgarians. As the higher summer temperatures coincide with longer periods with no rain, drought hardiness is becoming more important in our planting ideas. One of the most important factors in this is soil depth and composition. Where many landscape plants do poorly, the natives are fine. The difference between many suburban soils and native undisturbed soils that still sustain a living plant community is tremendous. Whether it is a grassland, riparian plant community, aspen groves, or northside groves of spruce and douglas firs, they all do better than most of their suburban counterparts. I have explained this in great detail with a recent series of essays on my website, krltreeservice.com. The essays are called What every tree owner needs to know to have happy trees.
Native trees
This is a very short list: White spruce, Douglas fir and Quaking aspen. The fourth native tree, the Balsam poplar, the big cottonwood of the river valley, is not recommended for residential property. A small tree, the Pin cherry, also thrives near here. Another small tree, the Canada plum also deserves mention.
Native shrubs
These all thrive here; in fact, they are so tough that many times they quickly outgrow their space allocated in a garden. Serious control may be required.
Tall native shrubs over 10 feet in maturity: Saskatoons, chokecherries, alder, river birch or black birch.
Medium size, could approach 10 feet in maturity: dogwoods, silver buffaloberry, wolf willow.
Short native shrubs grow to about 4 feet: prickly rose, prairie rose (about one foot), buffaloberry, snowberry, potentilla.
Introduced tree species
These are all large trees, so appropriate space is needed: green ash, American elm, Siberian elm, Manitoba maple; all can grow to over 50 feet in height. They have all proven themselves for decades as part of prairie shelterbelt plantings. We have yet to see mature heights from the Brandon elm; a smaller, tight vase shaped elm, it is recommended.
Medium-size introduced trees grow to about 30 feet high: Siberian crab (the old tree, not the fireblight-riddled new cultivars, especially the columnar selections); Urasian pear; Russian olive, from Europe and Asia, which is used extensively in the dry American west; native hawthorns, not the snowbird or Toba, which have a big problem with juniper/hawthorn rust; Amur and Tartarian maples, burr oak and Ohio buckeye.
Introduced shrubs
Taller introduced shrubs, all of which can grow above 10 feet: Tartarian honeysuckle; mock orange; the cranberry group, including the high bush, nannyberry, arrowwood and wayfaring tree; elders; forthysia; French lilacs; Japanese or ivory silk lilac; caraganas, except the variety called Sutherland because of trunk splitting; Nanking cherry, Double flowering plum.
Medium-sized introduced shrubs that grow to 5-6 feet: Spireas, some are short; also the false spirea, which is not a spirea; burning bush; principia; Russian almond; currants; ninebarks; Littleleaf or Korean lilacs.
Evergreens, Conifers
All of the following evergreen shrubs and trees are highly recommended. Conifers have small, thin needle-like leaves, which have a thick layer of wax on them to help retain water. This, combined with the economical use of water in their trunks, makes almost all conifer shrubs and trees excellent choices as the world warms up. Conifers evolved in rugged northern country, many times in or near mountain environments, with lots of snow in winter, wet springs, and hot, dry, intense summers. They are more water efficient/drought capable than their deciduous leafy cousins.
Conifer shrubs come in three sizes: ground-hugging or horizontal growth, globular, and upright or columnar growth patterns. The first never grow above a foot, the next have a 4-5 foot max, and the third, the columns or tear drop shapes, can go to 15-20 feet. Almost all of the “carpet” types of junipers are good, as are the mid-size juniper shrubs and all of the columnar juniper varieties. There are many, many varieties commercially available.
Large evergreen trees: Given time—decades or 100 years—these can attain great height, for the prairies, of approximately 100 feet. They are listed in descending order of mature height: white spruce, Douglas fir, Colorado spruce; then we drop down to the next size, 70-80 feet: Norway spruce, Colorado silver fir, and potentially Siberian larch could do this, though I haven’t seen it. The next level would be the 50-footers, with the Tamarack larch, Ponderosa pines, Eastern white pine, Scots pine, (another common shelterbelt tree). Below that we have the Austrian pine, perhaps the best pine for Calgary, at about 40 feet in maturity, followed by shorter trees, usually below 30 feet in mature height. Many of these I have listed are not native here; also, many have not been here for a long time, so mature height ideas can fluctuate. What they might attain in their native country could be very different here in the tree-stressful West. The rest of the hardy evergreen trees are: mountain pine, subalpine fir, balsam fir, Swiss stone pine, bristlecone pine. Whitebark pine and limber pine are close natives and, if you can find nursery stock, make beautiful natural formed “bonsai”-like trees.
