Trees and Shrubs
A tree you plant this year may still be standing when your grandchildren are grown. In Lethbridge it has to handle zone 4 winters, chinook swings, drying wind, dry summers and alkaline clay. Here’s how to choose trees and shrubs that will thrive, where to put them, how to plant them so they get a good start, and the provincial rules every elm owner needs to know.
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Choosing for Lethbridge
Four things kill more trees and shrubs here than anything else. A good choice handles all four.
Winter
We’re in Canadian zone 4. Choose plants rated zone 3 or colder for open, exposed spots; zone 4 plants for sheltered ones.
Wind
Brittle trees lose limbs, and broad-leaved evergreens dry out. Flexible, tough-wooded trees and small-leaved shrubs cope best.
Drought
About 375 mm of precipitation a year, with dry, windy summers. Once established, the best choices get by on occasional deep watering.
Alkaline clay
High-pH soil locks up iron, and some trees turn yellow between the leaf veins (iron chlorosis). Acid-lovers struggle; prairie natives don’t mind.
What it means for you: trees and shrubs native to the prairies and foothills, or bred on the prairies, already have all four covered. They’re the safest starting point, and they feed local birds and insects better than most imports.
Right tree, right place
Most tree problems in city yards start on planting day, when a cute little sapling goes into a spot that can’t hold the tree it’s going to become. Look at the tag for the mature height and spread, and picture that size in the spot.
- Overhead lines: under power lines, plant only shrubs or small trees that top out well below the wires. Large trees there end up hacked into odd shapes by line crews.
- Foundations: keep large trees at least 6 m from the house and smaller ones at least 3 m. Shrubs need a metre or more so air can move and the roof doesn’t drip on them.
- Sewer and water lines: poplars, willows and Manitoba maples have aggressive, thirsty roots that find leaky pipes. Keep them well away from service lines.
- Sun and snow: a big deciduous tree on the south or west side shades the house in summer and lets sun through in winter. Evergreens are best on the north and west, where they block winter wind without blocking winter sun.
- Neighbours and sidewalks: remember the spread. A tree on the property line will one day hang over both yards. Boulevard trees on City land belong to the City of Lethbridge; check with them before planting or pruning.
Click Before You Dig. In Alberta, every ground disturbance, even planting a single tree or driving a stake, needs a locate request first. Alberta’s locate service, formerly called Alberta One-Call, is now Utility Safety Partners. Request a free locate online through Click Before You Dig at utilitysafety.ca or by phone at 1-800-242-3447, at least three full business days before you dig. Utility companies then mark where their buried lines run. Hitting a gas line with a shovel is dangerous, and a cut cable can knock out service to your whole street.
What should I plant here?
Answer a few questions about your spot to see trees, shrubs and perennials that suit it.
Plant picker
Shade trees that do well here
| Tree | Size (approx.) | Why grow it | Watch for |
|---|---|---|---|
| Bur oak (Quercus macrocarpa) | 12–15 m | Native to the eastern prairies, zone 2–3. Deep roots, very drought and wind tolerant, fine in alkaline soil, long-lived. | Slow to start. Plant young; it’s worth the wait. |
| Hackberry (Celtis occidentalis) | 10–15 m | Zone 2–3. Tough, drought-tolerant street tree; handles alkaline soil and wind. | Needs good drainage; can be slow early on. |
| ‘Dropmore’ linden (Tilia × flavescens) | 10–12 m | Bred by prairie plant pioneer Frank Skinner at Dropmore, Manitoba. Hardy, tidy, pyramid-shaped, with fragrant early-summer flowers that bees love. | Appreciates a deep drink in dry spells. |
| Ohio buckeye (Aesculus glabra) | 8–10 m | Zone 3. Rounded tree with early flowers and orange fall colour. | Leaves can scorch in hot, dry wind. The nuts are poisonous to people and pets. |
| Schubert chokecherry (Prunus virginiana ‘Schubert’) | 6–8 m | Very hardy. Green spring leaves turn deep purple-red. A good small tree for city yards. | Black knot, a fungus that makes hard black swellings on branches. Cut out every knot in late winter, 15 to 20 cm below it, and bag or burn it. Suckers from the roots. |
| Amur maple (Acer ginnala) | 4–6 m | Zone 2. Small multi-stemmed tree with brilliant red fall colour. | Prone to yellow leaves (iron chlorosis) in heavy alkaline soil. Seeds itself around. |
| Japanese tree lilac (Syringa reticulata) | 6–8 m | Zone 3. Creamy white flower clusters in late June, after other lilacs. Good under some wires. | Flowers have a strong, privet-like scent some people don’t love. |
| Green ash (Fraxinus pennsylvanica) | 12–15 m | Native, zone 2, extremely tough; one of the most common trees in prairie towns. | Emerald ash borer, which has killed ash trees across eastern Canada and Winnipeg. It has not been found in Alberta, but don’t make ash your only tree. See ash below. |
Think twice about: silver maple and birch (both struggle with our dry heat and alkaline soil), Siberian elm (weak-wooded and seeds everywhere), and poplars and willows in small yards (huge, thirsty roots). And don’t plant a monoculture: a street of one kind of tree can be wiped out by one pest. Mix it up.
Evergreens
- Colorado spruce (Picea pungens): zone 2–3, very drought and wind tolerant once established, in green and the familiar blue forms. Needs room: 10 to 15 m tall and 5 m or more wide.
- Scots pine (Pinus sylvestris): zone 2–3, fast-growing, handles dry, poor soil. Develops orange bark and an open, character-filled shape with age.
- Mugo pine: low, mounding forms for foundations and rock gardens.
- Junipers: about the toughest evergreens there are, from creeping groundcover types to upright forms. Rocky Mountain juniper and creeping juniper are native to Alberta.
Winter burn and fall watering
Evergreens keep losing water through their needles all winter. On a sunny, windy chinook day they lose a lot, but the roots are frozen and can’t replace it. The result shows up in March and April as brown, dry needles, usually on the south and west sides.
- Water deeply in October, before the ground freezes. Soak the whole area under the branches.
- Water again during a long winter chinook if the ground has thawed and the hose can be drained afterward.
- Mulch the root zone with wood chips to hold the moisture in.
- Screen young evergreens on the south and west sides with burlap on stakes, not wrapped tight around the plant.
- Be patient in spring. Brown needles won’t green up, but the buds behind them are often alive. Wait until June before pruning anything out.
Flowering and hedge shrubs
Lilac
The classic prairie shrub: common lilac, the compact ‘Miss Kim’, and late-blooming Preston lilacs bred in Canada. Drought-tough once established. Prune right after flowering.
Potentilla
Small, tough and in flower from June to frost, in yellow, white, orange or pink. Handles sun, wind and dry clay.
Nanking cherry
Zone 2. Covered in pale pink blossoms in early spring, then small edible red cherries. Makes a good informal hedge.
Hedge cotoneaster
The prairies’ classic clipped hedge: dense, glossy leaves, orange-red fall colour, and very hardy.
Caragana
Zone 2 and almost unkillable in drought and wind; the old farmstead windbreak shrub. It can spread from seed, so keep it trimmed.
Dogwood
Red osier dogwood is native, with bright red stems that glow against winter snow. Likes a little more water than most.
Spirea
Easy, compact shrubs with white or pink flowers. Bridal-wreath types bloom in spring; low, pink-flowered types in summer.
Hardy roses
Canada’s own roses were bred for exactly our winters (below).
Roses that come back
Tender hybrid tea roses usually die in a Lethbridge winter. Canadian-bred shrub roses don’t. Agriculture Canada’s Explorer series, named after explorers, includes ‘John Cabot’, ‘William Baffin’ (a climber), ‘Henry Kelsey’ and ‘J.P. Connell’. The Parkland series, bred at Morden, Manitoba, includes ‘Adelaide Hoodless’, ‘Morden Blush’, ‘Winnipeg Parks’ and ‘Hope for Humanity’. Most are rated zone 2 or 3, grow on their own roots, and recover from the ground if a hard winter knocks them back. Alberta’s own floral emblem, the wild rose, is about as tough as a shrub gets.
Shelterbelts and windbreaks
Farmers across southern Alberta have planted shelterbelts for over a century, and the same idea works on a city lot. A windbreak doesn’t need to be solid. In fact, a partly open barrier works better: it slows the wind gently over a long distance, while a solid wall makes swirling eddies right behind it.
- How far it reaches: a windbreak slows the wind for a distance of up to about ten times its own height on the downwind side. A 3 m hedge shelters a strip of up to about 30 m.
- Where to put it: on the side facing the prevailing west and southwest wind, and on the north side against winter storms.
- Layers: on acreages, the classic design is a row of shrubs on the outside, then deciduous trees, then evergreens. In a yard, a mixed hedge of caragana, lilac or cotoneaster with a spruce or two behind it works on a small scale.
- Snow: windbreaks also catch snow. Snow piles up just downwind of them, which is good for a perennial bed and bad for a driveway. Plan where you want the drifts.
Lethbridge averages 116 days a year with gusts of 40 km/h or more. Check the live wind speed and direction on the forecast page, and read more on our growing conditions.
Planting a tree the right way
Spring (May to early June) and early fall (late August to September) are the best times. Here’s the method that gives roots the best start.
- Request a locate first, and wait for the marks.
- Find the root flare. That’s where the trunk widens out into the roots. Nursery trees are often buried too deep in their pots; scrape away soil until you find it.
- Dig wide and shallow. Make the hole two to three times as wide as the root ball, but only as deep as the root ball, so the root flare ends up level with the ground or slightly above. Roughen the sides of the hole in clay so roots can push out.
- Free the roots. Take off the pot. Tease out circling roots or cut through them. For burlap-wrapped trees, remove any wire basket and cut away as much burlap and twine as you can once the tree is in the hole.
- Backfill with the soil you dug out. Mixing in lots of rich amendment can make roots stay in the hole instead of spreading out. Break up clods and firm gently.
- Water deeply as you fill, to settle the soil and remove air pockets, then build a low ring of soil around the edge of the hole to hold water.
- Mulch 5 to 10 cm deep in a wide circle, keeping it a hand’s width away from the trunk. No “mulch volcanoes.”
- Stake only if needed, for a tall tree in an exposed spot. Use two stakes and wide, soft straps, tied loosely so the trunk can still sway. A little movement builds a stronger trunk. Remove the stakes after one year.
Watering, wraps and pruning
Watering young trees
A newly planted tree needs about two to three years to grow the roots it needs to look after itself. Until then:
- Growing season: a slow, deep soaking once a week (twice in hot, windy spells). A hose left trickling for 30 to 60 minutes beats a quick spray.
- Fall: one more deep soaking in October before freeze-up.
- Dry winters: Lethbridge winters can be nearly snowless, and chinooks dry the soil further. On a mild day when the ground isn’t frozen, give young trees and evergreens a drink. Water at midday so it soaks in before night, and drain the hose afterward.
Sunscald wraps
Thin-barked young trees (maples, lindens, fruit trees, mountain ash) can split on the southwest side when bright winter sun warms the bark by day and it freezes hard at night. Wrap the trunk with a light-coloured spiral tree guard from late fall to spring for the first few years, and take it off in spring.
Pruning basics
- Start with the three Ds: remove dead, damaged and diseased wood any time (except elms; see below).
- Most trees: late winter (February to March) while dormant, when you can see the branch structure. Maples and birches “bleed” sap in spring; the bleeding doesn’t harm them, but many people prefer to prune them in early summer after the leaves are out.
- Spring-flowering shrubs (lilac, Nanking cherry, forsythia): prune right after they bloom, or you cut off next year’s flowers.
- Summer-flowering shrubs (potentilla, summer spirea): prune in early spring.
- Cut just outside the branch collar, the slightly swollen ring where a branch joins the trunk. Don’t leave stubs and don’t paint wounds; the tree seals them itself.
- Never top a tree. Cutting off the main leader leads to weak, crowded sprouts and a hazard later.
Stay safe when pruning. Work from the ground with hand pruners, loppers or a pole pruner wherever you can. If you must use a ladder, set it on firm, level ground, have someone hold it, and never stand on the top two steps or lean out to reach. Never prune a tree that touches or is close to a power line; call the City of Lethbridge at 311 first. For large trees, hire a certified arborist.
Elms, ash and firewood: the rules
Dutch elm disease and the pruning ban
Dutch elm disease has killed millions of elms across North America, including much of Saskatchewan and Manitoba. It’s a fungus carried by elm bark beetles, which are attracted to fresh cuts and breed in dead and dying elm wood. Alberta has worked for decades to keep it out, and the province says it has the largest disease-free stand of American elm in the world. The province’s rules apply to every elm owner:
- No storing elm firewood. Storing elm wood is prohibited at any time of year unless it has been treated (bark removed and the wood kiln-dried or heat-treated).
- Dispose of elm wood right away, by taking it to your municipality’s designated elm disposal site. It may only be moved to go there.
- Don’t bring elm into Alberta. Bringing elm wood in from provinces with the disease, such as Saskatchewan, is illegal.
- Report suspect elms (leaves wilting and turning yellow-brown on one branch in mid-summer) to the provincial STOPDED hotline at 1-877-837-ELMS (3567).
Emerald ash borer
Emerald ash borer is a small metallic-green beetle whose larvae tunnel under ash bark and kill the tree within a few years. It has killed millions of ash trees in eastern Canada and has been in Winnipeg since 2017. As of this writing it has not been found in Alberta, and in 2025 the province added it to Alberta’s Agricultural Pests Act. The beetle mostly travels long distances in firewood.
What it means for you: buy firewood where you’ll burn it, and never bring firewood home from other provinces or from camping trips. If you’re choosing a new shade tree, pick something other than ash so the neighbourhood isn’t depending on one species. If you already have a healthy ash, there’s no reason to remove it.
A tree is an apartment building. Birds nest in the branches, squirrels live in the holes, insects hide under the bark, and fungi and worms work away among the roots. One big old tree can be home to hundreds of different living things.
Wonder: a tree grows one ring every year, a light band in spring and a dark band later in summer. What do you think a very thin ring means about that year’s weather?
Try this: find a tree stump or a cut log and count the rings from the middle out to find out how old the tree was. Look for skinny rings (dry years) and fat ones (good growing years). Then go and give a young tree a big drink of water.
Sources
- Government of Alberta, Dutch elm disease (overview).
- Government of Alberta, Dutch elm disease prevention: what you can do (pruning ban, elm wood storage, transport and disposal; STOPDED hotline).
- Government of Alberta, Agri-News, “Elm pruning ban starts April 1”.
- Utility Safety Partners, Damage Prevention Process: Homeowners Edition; Alberta One-Call Corporation is now Utility Safety Partners (news release, 2021).
- City of Calgary, Emerald ash borer; Parkland County, Emerald ash borer added to the Alberta Agricultural Pests Act (2025).
- City of Winnipeg, emerald ash borer tree removal news (2026).
- University of Saskatchewan, Patterson Garden Arboretum, Cultivars Developed by Prairie Pioneer Plant Breeders.
- North Dakota State University Extension, Ohio buckeye and tree handbook fact sheets.
- Natural Resources Canada, Plant Hardiness of Canada.