The quaking aspen (Populus tremuloides), a name that refers to how its leaves tremble at the slightest breeze, is a tree in the Willow family. Other common names refer to such features as its fall color (golden aspen), bark color (white aspen), or to a favorite habitat (mountain aspen). It's easily identified by its smooth, light-colored bark, interrupted at intervals by darker knots and horizontal scars. An even better identifying feature is its flattened leafstalks, which cause the leaves to "quake" when the wind blows. The leaves are rounded to slightly triangular, 3 inches across, and finely toothed. The flower/seedhead is a catkin. Quaking aspen isn't the best tree for every landscape, but, if you wish to grow it, the best time to plant one is spring, after the last frost date in your area.
|Common Names||Quaking aspen, trembling aspen, American aspen, golden aspen, mountain aspen, trembling poplar, white poplar|
|Botanical Name||Populus tremuloides|
|Plant Type||Deciduous tree|
|Mature Size||20 to 50 feet tall|
|Sun Exposure||Full sun|
|Soil Type||Well-drained, fertile|
|Soil pH||5.5 to 8.0|
|Hardiness Zones||1 to 6, USDA|
|Native Area||North America|
Quaking Aspen Tree Care
An iconic tree of the Rocky Mountain states, quaking aspen is a high-maintenance plant, due to its ability to spread, unless it is a large stand of quaking aspen that you desire (over time). Such a stand (colony) could be suitable for an isolated area of your property. But to grow a single quaking aspen as a specimen plant or shade tree, you must continually remove any new plants that pop up from the root system to avoid growing unwanted trees and to protect foundations and septic systems. It's not technically invasive, but it is referred to as a colonizer, sending out many genetically identical trees in the immediate vicinity.
Grow quaking aspen tree in full sun for best results, although it does tolerate some shade.
Provide quaking aspen with good drainage. An average garden loam is sufficient.
For best results, keep its soil evenly moist.
Temperature and Humidity
Quaking aspen does not handle heat and humidity well. It is not suited to regions such as the American Southeast.
Quaking aspen performs best in moderately rich soil. Fertilize it with a complete fertilizer in early spring for an extra boost. Follow instructions on the fertilizer package precisely. The instructions will spell out exactly how much fertilizer to use, an amount that varies according to tree size. Over-fertilizing can burn your plant.
Types of Aspen (Poplar) Trees
There are a number of trees in the Populus genus. They are commonly referred to sometimes as "poplars," sometimes as "aspens." Examples include:
- Japanese poplar (Populus maximowiczii): A columnar tree with the virtue that it does not produce suckers, thereby reducing maintenance
- Lombardy poplar (Populus nigra): A columnar tree often planted along property borders, but it does produce suckers
- White poplar (Populus alba): Although Populus tremuloides is also sometimes called "white poplar," Populus alba is a distinct species. It is valued for its silvery leaves, but its downside is that it's invasive.
The best time to prune quaking aspen is winter because this is when the tree is dormant, meaning the tree will tolerate cuts better. Quaking aspen will need to be pruned after limbs have been damaged by heavy winter snowfalls. The damaged limbs should be pruned back to the collar. Dead or diseased branches should be pruned off whenever you spot them.
The only need for discretionary pruning is generally when you are growing the tree in an area where you will be walking regularly. You may wish to remove low-lying limbs there (rather than having to duck under them when walking). Again, prune such branches back to the collar.
Propagating Quaking Aspen Trees
Quaking aspen spreads naturally through its root system, developing into large stands over time. In such a stand, one tree is a clone of the next. The trees are also dioecious, so there are distinct male and female colonies. Because quaking aspen trees do propagate themselves so readily through their root systems, you can take advantage of this fact to acquire new trees. Simply dig up offshoots from the original tree and transplant them to a suitable location in your landscape. This is by far the easiest way to propagate quaking aspen.
How to Grow Quaking Aspen Tree From Seed
You can also grow it from seed, but it's a bit more trouble. If you go this route, at least simplify matters by buying the seed rather than trying to harvest it from the wild. The latter is difficult for beginners because the pollinating male plants don't look that much different from the seed-bearing female ones (both produce catkins).
Once your seeds arrive, fill a planting container with seed-starting medium and moisten it. Sow the seeds right on top of the seed-starting medium; don't cover them with soil. Keep the medium moist; placing the container in a plastic bag will help trap moisture. Seed will germinate in 24 hours. Place the container in a window for light. Plant outdoors after all danger of frost has passed.
Quaking aspen is cold-hardy all the way to zone 1, so no extra care is required to overwinter it.
Common Problems With Quaking Aspen Tree
Quaking aspen is prone to attacks from insects and diseases.
Quaking aspen is susceptible to infestations of poplar borers. It is the larvae that do the boring, and their holes invite damaging fungi into the tree. But these beetles typically attack trees that are in poor health. Thus the best control measure is to keep your tree in good health by making sure its light levels, irrigation, drainage, etc. are adequate.
Powdery Mildew Disease
Quaking aspen can be attacked by powdery mildew disease. Quaking aspen likes evenly moist soil, but you have to strike the right balance between dry soil and soggy soil. Soggy soil invites fungal diseases. Likewise, don't get the leaves wet when watering. Also water early in the day, so that excess water evaporates before nightfall. Practicing good garden hygiene can also help prevent this fungal disease. Remove and dispose of any diseased leaves or branches.
Does quaking aspen have aggressive roots?
Does quaking aspen tree have nice fall foliage?
Yes. It turns a brilliant golden-yellow color in fall.