September Tree of the Month-Aspen
Anyone experiencing peak Aspen glow in the Rocky Mountains has thought about growing aspens once they get back home. Unfortunately, if “home” happens to be St. Louis, you are most likely going to be disappointed.
Believe it or not, aspens are actually native to Missouri. So why do they struggle here? Because the northern edge of Missouri, where they are native, is a full zone cooler than here in the Lou. Missed it by THAT much!
Drive up to Kirksville, Missouri, or Southern Iowa, and although we are just a few hours away, you will see outstanding specimens of Douglas fir, and yes, aspens where they can grow 20-50′ high. However, a few specimens are holding ground around the St. Louis area.
At the Missouri Botanical Garden, a small stand planted in 1979 was spared during the construction of the Children’s Garden and is still alive. A private residence in Sunset Hills has a 12-year-old specimen obtained from thriving aspens in Spanish Lake. And recently, the new Brentwood Park is giving aspens a try near the playground.
Part of the difficulty with aspens is that they form colonies…huge ones. Those aspen stands you see on a Rocky Mountain slope can all be connected underground into one large organism. The 106-acre Pando aspen grove in Utah is one of the largest living organisms on the planet. Because of this colonizing trait, transplanting is tricky…if not fatal for any severed specimen. Aspens don’t often produce viable seeds, and collecting them is difficult from the fluffy catkins. Another interesting fact about aspen stands is that they are dioecious, meaning separate male and female plants. That means every colony of aspens consists of either all male clones or all female clones-another reason why viable seeds are challenging to come by. Most growers propagate aspens from root cuttings, which is faster than seed, with uniform, identical results.
Despite aspens preferring full sun, I believe the key to growing aspens in St. Louis is some shade, especially from the blazing afternoon sun. Both the MBG and the Spanish Lake aspens are in shady locations. We’ll see if my theory is correct with the Brentwood Park aspens planted in full sun and surrounded by concrete. Moist, but well-drained soil is also preferred.
Aspens have flat petioles that catch even the slightest of breezes, making the leaf wave, or “quake.”
So, what about that common name, “quaking” aspen…well, a close examination of an aspen leaf will show that the petiole, that stem that attaches the leaf to the branch, is flat versus rounded like other leaves have. This shape can catch any breeze and therefore make the leaves wave, or “quake.” The closely related cottonwood trees also have flat petioles, which is why those leaves quake or wave in the slightest breeze. You can see those Colorado aspens waving “Hello” in this video sent by Lisa Neiley below!
What I love about this plant;
-It’s native!
-Stunning fall color.
-Interesting colonizing trait.
-Beautiful white bark.
What’s not so great;
-Will eventually form a colony with its suckers, which, in the wrong place, can be a problem. Place it accordingly to keep it a low-maintenance plant. The few living stands in the St. Louis area seem to be slower to sucker.
-Prone to multiple pests and diseases, especially when stressed. (Like by a St. Louis summer!) Please give it some shade, especially from late afternoon sun, and water regularly.
-Comments or questions? Email Garden-Lou at gardenloustl@gmail.com
Words and photos by Jo Batzer
© Jo Batzer, garden-lou.com-2025, All rights reserved.
-Comments or questions? Email Garden-Lou at gardenloustl@gmail.com
Words and photos by Jo Batzer
© Jo Batzer, garden-lou.com-2025, All rights reserved.
