Prairie Tested Trees

The Western Nursery Growers Group has developed a recommended tree list that was based on the results of the WNGG tree trial that ran for eight years (2008-2016) and/or from WNGG member’s personal experiences when growing these trees. The trees are classified into four categories: Recommended, Marginal, Not Recommended and trees that Need More Information. A detailed description of each of these categories is provided below the chart in the Legend section.

The trees in the WNGG tree trial were tested at four main sites: Strathmore, AB (Alberta South), Edmonton, AB (Alberta North), Portage la Prairie, MB (Manitoba South) and Saskatoon, SK (Saskatchewan & Central Manitoba). All these trees were grown in a cultivated field, located at a commercial tree nursery and were maintained the same way the rest of the other non-trial trees were grown.

The chart below should be viewed as a guideline rather than a guaranteed fact of the performance of each tree growing in a specific region. There are so many factors effecting tree performance that no guarantee can be expected when using the WNGG recommended tree chart.

Legend for the WNGG Tree Trial summary chart.

Recommend (R) – trees that performed best and sustained no more than 10% winter kill during the trial period. These trees must have a high to complete resistance to disease and insects, well adapted to prairie soils, display a dominate ornamental value and be commercially available.

Marginal (M) – trees that sustained between 10 – 50% winter kill during the trial period. These trees need regular pruning to take the dead wood out.

Not Recommended (NR) – trees that sustained more than 50% winter kill during the trial period and/or are very susceptible to insects and disease. These trees are not recommended to be planted in the prairie region.

Need More Information (blank cell) – trees that need to be retested or put in the trial for the first time.

1. Anthracnose is a fungal disease that infects the leaf veins and surrounding areas on leaves and seeds of shade trees. This disease does not cause death but looks unsightly. More prevalent in years when the springtime is cool and moist.
2. Ash Flower Gall Mite stimulates a great proliferation of flower buds on male trees. This creates groups of deformed flower buds that remain on the tree after leaf fall and for many years.
3. Black Knot is a fungal disease on cherry trees such as Schubert chokecherry and wild chokecherries. The first sign of the disease appears as a green swelling on the branch that eventually increases in size and matures as a dark elongated gall like structure. It appears in fast growing cultivars such as Bailey Select that are many times more susceptible than the slower cultivars such as Spur and the Classic Schubert cherries.
4. Bronze Leaf Disease (BLD) is a fungal disease that over many years will cause death to many aspen cultivars. Swedish Columnar (P. tremula erecta) and Tower aspen (P. x canescens ‘Tower’) are two cultivarsalong with its hybrids are very susceptible to BLD. The most tolerant aspens are the pure species of trembling aspen (Populus tremuloides), largetooth aspen (P. grandidentata) and silver aspen (P. alba). The first sign of BLD are bronzing of the green leaves in August and those bronzed leaves curl up and remain on the tree during the winter and the next season.
5. Cholorosis affects the performance of the tree in growth and vigour. The sign tha your plant is suffering from iron chlorosis is when the leaf turns yellow while the veins still retain the normal green colour. Iron chlorosis develops when the tree is unable to absorb enough iron even though there may be enough iron present in the soil. Application of iron chelates makes the iron more available to the roots.
6. Cottony Psyllid is an invasive insect that attacks black and Manchurian ash trees during the late spring to early summer months. The nymph stage of this insect will suck the goodness of the leaves resulting in trees with curled up green leaves. The vigour of the tree is severely compromised and the tree will eventually die from repeated attacks each year and/or the attacks from a secondary killer, the ash borer.
7. Fireblight is a bacterial disease that will eventually kill the tree. The early signs of fireblight look like a branch has been torched by a flame and black leaves and stem remains in a curled state.
8. Leaf Scab is a fungal disease that attacks trees in the apple, crabapple and pear family. Leaf scab appears as dark blemishes on the leaf and fruit in mid-spring. This disease will severely reduce the growth of the tree since many leaves and fruit drop before autumn. The infected fruit are not good to eat. Many new varieties of apples, crabapples and pears are highly tolerant or are totally resistant to leaf scab.
9. Slow Annual Growth.
10. Stem Canker is a fungal disease that is first detected when the bark on poplars turn yellow, brown or black. The wood around the canker then begins to deteriorate and the stem is either girdled or weakened and the tree eventually breaks.
11. Sunscald and Frost Cracking are caused when the late winter sun warms up the south or west side of the trunk and the tree’s trunk inner and outer wood expand at different rates. When the severe cold winterwinter temperatures returns there is too much difference in expansion rates and a major stress occurs resulting in cracks and splits in the bark.