Trembling Aspen (Populus tremuloides)

A tree that is often clonal in its reproductive nature can challenge our concept of a tree and make us fall further in love with the beauty of our kin, the river valley’s Trembling Aspen. What do we mean by “clonal”? Think of a tree that doesn’t make “babies” through pollinated (fertilized) seeds but rather by sending up new shoots off an existing root system. Gardeners might call this form of reproduction “suckering”.

Look at the picture below. Do you see a tree or a whole bunch of trees?

The people that named it saw all of the vertical trunks as one large tree. It’s a stand of trees sharing the exact same DNA: clones of one old Trembling Aspen. The tree stand was genetically tested and proved to be exact copies of one DNA type that spread out across the land to form 106 acres of an aspen “tree”. It is thought that some of the root system dies and is renewed under the ground. The above-ground shoots or “trees” also get “born” and die. The clonal trunks then end up being of different ages and sizes and not as old as the original root system — but they all still share the original genes. This is why the locals saw this stand of clonal aspen as one “tree” and named it Pando. They understood the trembling aspen was not only a beautiful tree that dances in the wind, but a tree that can often be very old, very large and most likely, very wise.

Regardless, if you see one tree or many trees, we hope you can start identifying similar stands of trembling aspen in our river valley. ERVCC wants trembling aspen to be better seen, loved, and honoured. 

Trembling Aspen, it is a deciduous tree, native to our cool, Edmonton climate. The tree is also dioecious meaning only female reproductive parts exist on female trees with only male parts on male trees. You will have to look to another river valley tree, the Larch, to find an example of a tree that has both sexes on the same tree. Larch trees and other trees with both sexes found within the same tree are called monoecious.

The Trembling Aspen tree, as stated, has reproductive parts from just one sex or the other. But, rather than reproduce sexually with the help of the wind and other pollinators, aspen most typically reproduce by budding off the root system to form a new tree. It is in this manner that it can produce a large stand of shoots all sharing the same genes often with a shared root system to create clonal stands like Pando.

First Nations of amiskwaciy-wâskahikan have a long relationship with aspen. The tree was and continues to be used for ceremony, food, medicine, and wood. Settler Glady’s Reeves picked the aspen as one of the first trees to transplant onto Edmonton’s boulevards as part of a 1923 beautification movement. It is of interest that the “Populus” in Populus tremuloides comes from the fact that many cities planted the tree in central city squares. Tremuloides may not rule on boulevards any more but they stand proudly and predominantly in our river valley.

With Pando, it is thought the root system is as old as the oldest stem(tree) because the root system below the ground gets as much renewal as the above-ground growth. The individual genotype of Pando, however, has likely been around since the last glaciation. So Pando is not strictly a single organism but has reproduced and renewed asexually from the same genetic origins. Regardless, aspens really challenge our concept of what we mean when we say “tree.”

ERVCC and Shrubscriber are interested in having river valley enthusiasts report on aspen that they think could be clonal stands. We will then work to secure funds for genetic testing to be done to discern which stands are clones. In other words, stands in which each trunk in the stand has the same genotype.

We are setting our intentions and will ask an Elder to consider what might be an appropriate ceremony for the aspen in our valley. Perhaps a naming ceremony for a stand of clonal Aspen? In the meantime, The Long Tree Society is asking how we can develop a culture prepared to steward trees that can live to be over 1000 years old. ERVCC believes this is the kind of cultural work is needed to properly honour, steward, and learn from our river valley and our river valley kin.

So, the next time you walk by a group of aspen trees in the spring and you see they are all the same sex, they might be clonal. If you believe you have spotted a clonal stand, please let us know.

Below are some tips for spotting a clone:

• They leaf out at the same time

• They are all the same sex

• They turn colours at the same time in fall

For identification help on how to discern if a Populus tremuloides is a girl or a boy please go to the website of Plant Watch run by ERVCC member Elisabeth Beaubien. Be forewarned, just to show you how tricky and awesome the trembling aspen can be, we also note that in very rare conditions the tree will have both male and female parts, proving once again, sex is not binary. Let us know if you find such a tree.

It is going to take a bit of observation, research and even DNA testing to know exactly what we are seeing in Edmonton’s river valley when it comes to witnessing stands of beautiful aspen. Tree researchers theorize the stands of aspen in the valley are more mixed than the Pando clone. Instead of having one clonal stand of aspen there might be a few clones of family members standing side by side. Only DNA testing can help us confirm if a large stand is all one clone or not. Lets find out!