- Written by Kevin R. Lee Kevin R. Lee
- Published: 12 January 2020 12 January 2020
Evergreen, what a great name, trees that are forever green. Evergreens are conifers; they retain their leaves, needles through periods of years. Cone bearing plants, their flowers, such as they are, are on separate parts of the tree. The male flowers produce pollen, the female flowers at first are beautiful miniature cones, often purple in color. And later are the mature cones with the seeds tucked down inside, tightly between the scales of the mature cone.
Evergreens are ancient plants, as old as 300 million years. They are simple in design, very tough and prefer more northern, cooler climates. The great taiga, a biome circling the planet below the North Polar region, is mostly evergreens.
In Calgary we are blessed with a good count of evergreens that thrive here. One ironic note is the fact of the lodgepole pine, native as close as Bragg Creek. It is the pine that fails more often than any of the introduced species. In the forest they always grow together in great communities, and the needles, dead trees and all other parts of natural forest floor duff seem to keep them strong. A single planting in a Calgary lawn is the opposite of that.
Calgary's Best Evergreen Trees:
⦁ Mugo pine
⦁ Scots pine
⦁ Bristlecone pine
⦁ Swiss stone pine
⦁ Eastern white pine
⦁ Ponderosa pine
⦁ Austrian pine
⦁ White spruce
⦁ Colorado blue spruce
⦁ Norway spruce
⦁ Colorado silver Fir
⦁ Balsam Fir
⦁ Sub-Alpine Fir
⦁ Douglas Fir
Two more conifers, but not evergreens:
⦁ Siberian Larch
This list is not exhaustive. I could list many more, but have focused on the best, the hardiest trees, the trees with the least problems. There are many smaller and dwarf cultivars that are available and these small evergreens can add amazing interest to a garden, but that, my friends, is another post.
Calgary Pine Trees:
⦁ Mugo pine, Pinus mugo, is a Swiss import, very hardy -- there are several different types. Some grow fast, some slow. If you want a slow growing compact form and you buy a fast grower you will not be happy. Needles in groups of 2, height from 2 feet to 50 feet.
⦁ Scots pine, Pinus sylvestris, is a prairie standard. very hardy and drought tolerant. Beautiful exfoliating orange bark. Needles in groups of 2. Can grow to a 50-foot tree.
⦁ Bristlecone pine, Pinus longaeva and Pinus aristata, is an import from the dry American S.W., slow growing, thick needle growth. Needles in groups of 5, a 25-footer is a big one.
⦁ Swiss stone pine, Pinus cembra, another Swiss import, beautiful tight smaller narrow tree. 25 feet of height is a big one. Needles in groups of 5. Bright pewter bark.
⦁ Eastern white pine, Pinus strobus; amazingly, this eastern forest giant does quite well here. Logged extensively in the east, these were the great masts of the Royal Navy. Smooth grey bark, needles in groups of 5. Graceful.
⦁ Ponderosa pine, Pinus ponderosa, a giant from the B.C. interior, is fully hardy here. I have never seen one taller than 30 feet. In maturity, large orange corky plates of bark, lovely. Long needles in groups of 3.
⦁ Austrian pine, Pinus nigra, another European, maybe the best pine for Calgary. A full wide crown, beautiful silver/pewter cork bark. A large one would get to 40 feet. Needles in groups of 2.
Calgary Spruce Trees:
The next major group of evergreens is the spruce, tall, pyramidal, tough and long lived. Spruce trees can live in the right conditions for hundreds of years. Spruce logged in Hidden Creek in southern Alberta were 500 years old. The oldest planted, still extant spruce are in our oldest neighborhoods. Mount Royal is a good start if you are hunting for giants. The oldest are at least 100 years old and some are close to 100 feet high.
These are not only words of awe and praise, they are also a warning. All non-dwarf spruce attain great size, even in 50 years. Many a house with a row planted along the south side soon became a house fully in the shade. To lose all your winter sun to an enthusiastic overplanting is not a good idea. That said, a single spruce well placed can be a joy to see year round.
⦁ White spruce, Picea glauca, the native tree, like all spruce has single needles They are never in groups, like the pines. As said above, these get big; if you have a good open location, then go ahead, they are tough, drought tolerant to some degree, and if watered occasionally, relatively pest free. They do have their problems and a weak tree infested with yellow-headed saw fly is in trouble.
⦁ Colorado blue spruce, Picea pungens, an import, thrives and is naturalized here. Available in a spectrum of colors from a flat green into the blues and even silvery blue. Inch-long stiff sharp needles and 3-4 inch long golden cones help identify the Colorado. Size and growth pattern are similar to the white spruce, usually a wider tree than the white. Very aggressive in the landscape, crowding space and light and hogging water resources. Choose your planting site very carefully.
⦁ Norway spruce, Picea abies,another import, is under-utilized and is a graceful beauty. Size and all other planting concerns mentioned above still apply. It is the shape of the Norway that is so attractive. The branches swoop up, they leave the trunk and arch upwards, creating a pleasing appearance. The Norway produces large unmistakable cones that can be 7-8 inches long with a 2 inch diameter.
Calgary Fir Trees:
The next group of evergreens is the firs. Firs are mountain and coastal trees, so here in Calgary the numbers are low. Of the true firs, only the Colorado silver fir, Abies concolor, has made a stand. In native Colorado they attain great height as most mature evergreens do; here I have never seen one taller than 45 feet. Bright silver bark with sap bubbles in the younger bark and nearly 2 inch long silver/blue needles give this tree a handsome look. This tree is severely underutilized in Calgary.
⦁ A fir very rarely planted here is the Sub-Alpine fir, Abies lasiocarpa, from close by in our mountains.
⦁ Another is the Balsam fir, Abies balsamea, a northern forest tree.
⦁ The Douglas fir, Pseudotsuga menziesii, is a single species with no related tree family here. These are not true firs; scientists call them false firs. The two varieties here in western Canada are magnificent trees. The coastal giant is well known (have you visited Cathedral Grove?); most of those preserved giants are Douglas ir.
⦁ Here on the eastern slopes we are blessed with the rocky mountain Douglas fir. Calgary's Douglas fir trail is a great place to meet your elders. Many of the largest trees are at least 500 years old! Planted in the landscape the rules that apply to spruce trees would work here also. Very tough and trouble free tree. One feature of the cone can be used for 100% correct identification. Between the cone scales is an additional tissue called a bract. This forked snake's-tongue-shaped brown tissue is present only on Douglas fir.
Calgary Larch Trees:
⦁ Our last group of conifers is the larch. Larch do something no other conifer does. Each fall they drop their needles, but not before an amazing color change from a warm green to a canary yellow. Ever been to Larch valley? Something to see! The larch of the mountains, Larix lyallii, does not grow here but two of its cousins, one from Europe, thrive here.
⦁ The tamarack, Larix laricina, is native just north of here and as far east as Hudson's Bay. A classic conical evergreen form, the tamarack is a strong tree, able to deal with wet conditions. Its native setting is near boggy country. Tough and nearly problem free, it is greatly underused here. Excellent fall color.
⦁ The other larch is the ever popular Siberian larch, Larix sibirica, and if you know a larch it is probably this species. This conical shaped conifer has quite a wide base when the oldest lower branches are left alone. The branching habit is somewhat like the Norway spruce and they swoop, or lift up towards the branch tips. Very hardy and nearly problem free, the Siberian larch is a great choice, the big bonus being that they allow winter light through, so can work well as a summer, south side shade tree.
Most trees that get the water they need in order to have a strong immune system are trouble free; however, there are always exceptions.
Spruce trees, no mater how healthy, are preyed upon by a couple of insects. The first is the white pine weevil, a terminal [shoot] weevil that causes the die-back of the tree's leader. Invisible at the top of a spruce, they will not be seen until the leader starts to turn brown and dry up. This creates a problem for the tree because it will have to form a new leader. Usually a group of branches, the whorl just below the dead top, competes for the job as leader. It is best to choose the strongest, most central, of the new leaders for the job and remove the competitors. Both white spruce and Colorado spruce are affected.
The other insect is called the yellow-headed saw fly. The first you will see of them is at the larva stage, small green and black striped caterpillars with orangeish heads, near spruce branch tips. They are there to feed on the soft needles of the new growth. They chew the needles right down to the base. If enough of the saw flies are present they move from the new needles into the older parts of the tree, happily munching as they go. This normally doesn't happen until the second or third year of an infestation. At this advanced stage of lost leaf mass, the tree will soon die. Do not let the yellow-headed saw fly get established at your tree, as this is one insect that can outright kill a tree. Both white spruce and Colorado are attacked.
The next two common problems of spruce are usually seen only on drought stressed trees. In fact, the presence of spider mites and Cooley spruce gall adelgids can be used as a yardstick to measure the overall health of your tree. The presence of these insects means you need to water more.
Spider mites are tiny, and nearly too small to be seen. If lower branches on a spruce are discolored and have tiny webbing among the needles and stem, your tree has spider mites. The webbing is not the size of normal activity of spiders; these small webbings give a branch a cloudy, hazy look. They are very small. Place a sheet of white paper below the branch, tap the branch and the tiny mites will fall onto the paper where you can see them. The solution is to water more, increasing the tree's ability to fight its own battles. Both white and Colorado spruce are affected.
The Cooley spruce gall adelgid, a woolly aphid, is common in the west. The result of its activties is small deformed galls on the end of spruce shoots. These galls and the shoot tip die and form a dry spiney miniature pineapple-looking persistent gall. That is the extent of the damage and the tree carries on. The galls and especially their number on any tree are a strong indicator of drought stress. Well-watered trees never have very many.|
The last common problem is caused by a fungus, cytospora canker, or Leucostoma kunzei. Cytospora preys on drought-stressed spruce, especially the Colorado and the white spruce. First indication is a branch's color change, becoming dull looking. Later the needles will turn brown and fall off. Inside the tree near the trunk, the branch will be dripping sap. The sap stain around the canker site will turn a silvery white. This dripping sap from the canker can infect branches below. As soon as the presence is detected the affected branch should be removed. Water more. The drought-stressed tree is unable to defend itself; well-watered trees never get cytospora.
Pines, like most conifers, are mostly trouble free. Here are a couple of common problems to look out for.
Pine needle scale is a sap-sucking insect that adheres to the needles of pines, especially mugos. Look for white spots on the needles. Most vigorous plants never see this. Try changing your watering habits and if they persist, perhaps get it treated. June is usually the month when the young scale insects have hatched and are crawling to new feeding sites. Be careful with identification on bristlecones, which have naturally occurring deposits of sap on their needles. These sap granules have a wonderful peppery smell when handled.
Western gall rust of pines is most common on mugos, although it can also occur on ponderosa, Austrian and Scots pines. Look for round enlarged areas on the trunk and branches. These woody galls can persist for years. Each May spores are produced that easily reinfect other areas of the tree/shrub. The cure is to prune out the galls. If this is left unnoticed for years, the pruning could get disfiguring.