Tips for choosing trees and shrubs

Plan before you plant

Trees and shrubs are the "bones" of any yard or garden. They beautify your outdoor space, provide habitat for birds and insects, improve curb appeal and even increase your property value. 

The old saying "select the right tree for the right space" really holds true. Every plant has its own basic needs for light, moisture, soil and space. When one or more of those needs are not met, the plant will not thrive. The plant becomes stressed and in turn, is more susceptible to insect and disease problems. 

Choosing a tree or shrub can feel daunting, especially if you are a new gardener. There are hundreds of choices, but only some will thrive in your backyard environment and suit your personal preferences. Trees and shrubs are an investment in the future and a little planning can avoid problems in the long run. Here are some tips to help you narrow down the list and choose wisely.

Safety

  • Dial before you dig - find out the location of underground utilities. Utility companies will mark the location of underground services such as gas lines upon request.
  • Look up! Are there overhead power lines above that will interfere with a tree when it is mature? What about clothes lines, overhanging eaves or other obstacles? Will a mature shrub block your view from a window. If any of these situation apply, either choose a smaller tree or find a better location.
Know your plant hardiness zone
  • Trees and shrubs are given a Canadian Plant Hardiness zone rating according to your location. For example, Saskatoon is in Zone 3b, so select trees and shrubs that are 3b or lower rating. Climate is changing, so hardiness zones will rise in the future. To find your plant hardiness zone see: Canadian Plant Hardiness Zone Map
  • You can select trees and shrubs with a higher plant hardiness zone rating (such as Zone 4) in a protected microclimate (see below), but there is still a risk that the plant will not survive in severe weather. 

Microclimates

A microclimate is an area in your yard whose climate is different from the area around it. A microclimate may be warmer or colder, wetter or drier, or more or less prone to frosts. Factors that influence microclimates:

  • Buildings, fences and/or shelterbelts can slow prevailing winds and hold more heat than open areas. 
  • The south side of buildings and the areas adjacent to paved areas absorb heat during the day and radiate it at night.
  • Open areas subject to strong prevailing winds on the prairies can desiccate some plants such as cedars. 
  • Low-lying areas tend to stay moist and can be "frost pockets" in early spring or fall. Some trees, like birches or willows thrive in moist conditions, while others, like most evergreens cannot tolerate constant moisture.
  • The top of a sloped area tends to drain water quickly and may be persistently dry. Choose plants that are more drought tolerant and apply mulch after you plant.

Soil

  • What kind of soil do you have? Clay soil holds on to moisture, while sandy soil drains quickly. Some plants have particular preferences when it comes to soil while others are fairly adaptable.

Sunlight

Sunlight is one of the most important factors in the health of a tree. There are only a handful of trees and shrubs that will perform in shady conditions. Most trees need a lot of sunlight and this is especially true of fruit trees. Observe the area and count the number of hours of sunlight it gets during the day.

  • How many hours of sun does the spot get per day?   

Space and placement

All plants grow to a genetically determined height and width. They also need space below ground to accommodate a healthy root system. Well chosen and properly spaced plants are much less prone to insect and disease problems caused by lack of air circulation, increased humidity, shading and competition from other plants.

  • Consider your property line when selecting a site for a tree or shrub. Trees that grow wide enough to overhang into your neighbours property can be a nuisance. 
  • Avoid planting shrubs too close to fences and foundations. The area under the eaves (usually .5 to 1 meter) is naturally very dry. Take advantage of this area as a 'catwalk'. It's actually very convenient have this empty space in order to walk behind foundation plantings to prune or do maintenance on the house or fence. Once the plantings are mature, you don't even notice the 'catwalk' space when looking at the house or fence from further away. New plantings look puny at first, especially if you start with a small shrub, but you'll be glad you allowed space when the plant fills in. Fill in around the shrub plantings with drought resistant perennial plants or ground covers, and remember to mulch. 
  • Similarly, if you are planting more than one tree or shrub in an area, ensure that they are spaced so that the plants do not touch each other when they reach their mature size.
  • Avoid planting trees close to the foundation of a house, near septic tanks and/or waterlines. As a rule of thumb, tree roots extend between 1.5 to 2 times beyond the width of the canopy of the tree, depending on the species. Always consider the mature size of a tree before you plant. So for example, if you were to plant a linden which has a mature canopy width of 14 meters wide, divide that by half which is 7 meters from the trunk to the dripline. Then multiply by 1.5, which gives you 10.5 meters. Plant the tree at least 10.5 meters away from the foundation.
  • Shrubs have root systems that extend beyond the mature width of the shrub, but are not as extensive as trees. Shrub root systems also tend to be fibrous and lack a deep taproot. Adding 20% to the width is a good rule of thumb. So if you were planting a ninebark as a foundation planting, take the mature width of 1.5 meters, add 20%, which gives you 1.8 meters, then add the eave area (.5m). The total is 2.3 meters. Plant the ninebark so that the base of the shrub is 2.3 meters away from the foundation. 
  • Lawn growing up to the base of a tree or shrub competes with it for moisture and nutrients. Plan on removing a generous circle of lawn and top it with a thick layer of mulch after you plant. Your plant will love you for it. 
  • What is the maximum height and maximum width of tree or shrub that will fit your space?

Your personal preferences

Once you know the soil type, soil moisture, sunlight, maximum height and maximum width of the space, list the characteristics you prefer in a tree or shrub. 

  • Do you want a flowering tree? If so, is scent an issue?
  • Fruit or no fruit?
  • Evergreen or deciduous?
  • Fall colour?
  • Bark can be an attractive feature in some trees and shrubs and provide winter interest. For example, there are dogwood shrubs with either bright red or yellow branches. Ninebarks have exfoliating bark. Amur maple has bronze-coloured papery bark.
  • Know that many trees and shrubs benefit from proper pruning, especially fruit bearing trees such as apples, cherries and plums. New trees do not need to be pruned until they are 3 or 4 years old. Most evergreens should never be pruned, unless there is damage to a branch.
  • Trees come in all kinds of shapes: vase, oval, pyramidal (evergreens), ball, columnar (tall and thin) etc.
  • Foliage comes in all kinds of sizes and textures such as the fine thin leaves on a willow versus the thick coarse leaves of a viburnum. Some trees such as lindens have a thick canopy of leaves which provides deep shade while others are naturally more open like a scots pine.

How to research trees and shrubs and narrow down the selection 

Now that you know your site conditions and and have narrowed down your personal preferences, it's time to find the right tree or shrub. Here are good resources to help you narrow down your list. Fill in the "Tree and shrub selection checklist" below and refer to it when you research and shop.

Selecting a tree
  • A locally grown tree will adapt better to your site than a tree shipped from another province or country, because it has already adapted to the local climate. 
  • A smaller shrub (less than .5 meters) or tree specimen (less than 1 - 2 meters) will adapt better than a larger specimen.
  • Larger specimens (over 3 meters) are available and can be installed by the supplier using a tree spade. Although the effect is instant, they tend not to fare as well as smaller specimens grown naturally on the site. 

Tree and shrub selection checklist

  • Underground utilities have been assessed.      Yes/No
  • Plant Hardiness Zone number _____________
  • Sunlight: 
    • full sun
    • part sun
    • shade
  • Soil:
    • loam
    • clay
    • sandy
  • Moisture levels on site:
    • tends to be wet
    • tends to be dry
    • neutral
  • Microclimate:
    • ________________
  •  Space:
    • Maximum width __________
    • Maximum height __________
  • My personal preferences: (list all that apply)
    • _____________________
    • _____________________
    • _____________________
    • _____________________
    • _____________________
    • _____________________
    • _____________________
    • _____________________