Tuesday, February 27, 2018

Best Trees For Calgary; Burr Oak

     Few trees live up to the Burr Oak's, Quercus macrocarpa, hardiness, beauty and longevity. Although quite common in Calgary these trees are quite interesting and as Wikipedia states "...withstands chinook conditions in Calgary, Alberta." These trees are named for the burr-like quality of the acorn casing, also called Mossycup Oak, as seen above.

     Burr Oaks are native to North America from South Eastern Saskatchewan south to the Gulf Coast of Texas North East to Southern Ontario and scattered populations East to New Brunswick, that said these trees are adapted to a wide range of climates and soil types. They are the hardiest of the White Oaks (White Oaks have rounded leaf lobes, Red Oaks have pointy lobes) and adapted well to the prairies because of extremely long tap roots and resistance to grass fires. 

     There is a wide variety of leaf shapes with this Oak, some of my relatives in Saskatchewan believe there are different species of Oak there but this is not true. There are two "clinal variants" or geographic variability such as the smaller leaf of the Burr Oaks of the Northern Plains as well as easy hybridizing with White Oak and eight other Oak species in overlapping ranges. Above, I collected leaves of Oaks as I passed down a street in my nighbourhood, as we can see there is a tremendous amount of variability! I'm going to guess that any native oaks in Saskatchewan would have the small leaves while the ones purchased at a greenhouse are probably from a different gene pool with larger leaves.

     I don't know when the first Burr Oaks were grown in Calgary but there are a few old specimens around in Elbow Park, Mount Royal and Crescent Heights, in recent times these trees have become common boulevard plantings all over the city.

These two Burr Oaks are in Crescent Heights, a neighbourhood that is just over 100 years old now, they are some of the oldest trees I've seen here and probably around 40 feet tall (12 m). You can also see the variance in fall leaf colour and change time, one is completely brown and ready to drop and the other is still green with a little yellow and they are side by side.

     I found an old photo of my dad, our dog Misty and the Burr Oak I wanted so badly, planted in this picture circa 1982. 35 or so years later...

I have turned grey, have a new dog and the tree is around 25 feet tall!

     Here are some young Burr Oaks in a public park in the late summer. These trees are very easy to grow in Calgary as they are adapted to growing on the Northern Plains, avoid planting in a wet area. Growth rates are slow to moderate but once established need little care, withstanding drought and needing little pruning. Oaks do not have flowers but male and female catkins that appear with the first leaves in spring, they are fairly late in leafing out in our area, late May, but provide nice shade through the summer. Fall leaf colour varies from yellow to brown and timing can vary from early fall to staying green until a hard frost. The undersides of the leaves are a pleasant silver-white adding some interest in the summer. These trees are virtually pest free and if you live in an area with squirrels or Blue Jays the acorns will be gone before you'd ever have to rake them up!

The bark is dark and deeply furrowed adding winter interest as well.

The winter profile of the Burr Oak, these trees have a fairly consistent oval to rounded form ideal for yards parks and boulevards.

     If you want more Oaks! Harvest acorns as soon as they are ready to drop off the tree or just as they have dropped on the ground, the acorns lose viability quickly so plant immediately! I used a deep seed tray here and some good potting soil. Poke the acorns about a 1/2 inch below the soil and water lightly. Find an out of the way spot in your yard that will get good snowcover and will not get trampled by dogs or people also cover with wire mesh or a cage to prevent squirrels they LOVE these nuts! This process is called "stratification" and most of our tree seeds need this process of several days of freezing weather to germinate. Keep moderately moist thru the fall and wait till spring...

Around the end of May or so the little trees should start sprouting and viola new oaks!


     If you're looking for a legacy tree that your grandchildren's grandchildren can enjoy this is it, these trees can live 300 to 400 years! It's a nice idea that something you plant today can be enjoyed by so many generations in the future, giving oxygen, shade on summer days and acorns for wildlife. Except for leaves to rake up these trees are practically maintenance free. So if you're looking for a shade tree or just a dependable tree that needs little from you this is for you. 

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