Posted by shane - July 25, 2010 - A-Z Plant Maintenance, Shrubs, Trees - No Comments

River Alder at Sylvan Lake

Alder is one of my favourite trees, mainly because red alder (Alnus rubra) was the first species on which I attempted to prune.  Before I became an arborist, I worked in the logging industry on the coast of BC, flying in and out of remote locations to assess the quality of logs for various forest companies.  I was stationed in the Prince Rupert region one summer, and during some time-off, I took a hike onto an old clear-cut that had been logged 5 years earlier.  To my amazement, the compacted logging roads within the clear-cut were absolutely thick with red alder saplings.  I decided to try an experiment where I would selectively thin out a 40 foot length of roadway, and prune the remaining trees.  I wanted to see if spacing the trees would benefit their growth and development, compared to the rest of the road that I left untouched.

I definitely made a lot of pruning errors during that experiment.  I returned to that logging road for the next three years and continually spaced and pruned “my” trees.  Despite my mistakes, the results were amazing.  My alders were about three times the diameter of the surrounding trees, vigorously growing, tall, and healthy looking.  The surrounding alders were crowded, thin, and the “forest” looked sickly.  It was the first time I saw first hand how regular maintenance can have a tremendous impact on the trees’ health.  That experiment inspired me to return to college and become an arborist.

Prairie Species

Alnus tenuifolia (River Alder)

River alder is sometimes seen in Prairie gardens.  I planted two in my yard to remind me how I got started in the business.  I also think they’re very nice bushy shrubs.

Alnus hirsuta ‘Harbin’ (Manchurian alder)

This is a nice tree that tolerates wet sites and partial shade.  The mature form is 30′ high by 20′ wide.

Pruning Time

Dormancy or after full leaf emergence in the summer. Alders generally do not require heavy pruning to maintain a very nice branch structure.  As a result, the time of pruning is not critical.


Annually, remove dead and damaged wood, crossing, rubbing, and inward growing branches each year to ensure a healthy structure.

Irrigation & Fertilization

Alders prefer moist, well-drained soils.  They are nitrogen fixers and fertilization is unnecessary unless specific nutrient deficiencies appear.

(c) 2010 Shane LePage, Wild Rose Garden & Tree Service Inc., Red Deer, AB