Stands of bright gold aspen (Populus tremuloides) shimmering in the sunlight are a spectacular sight, so it is no surprise that many people plant aspen in their home landscapes. Aspen are fast growing and relatively short-lived relatives of cottonwoods and poplars. Ranging from 40 – 65 feet tall, they have a smooth white trunk and bright green, heart-shaped leaves. Female trees produce 2-inch catkins that develop into tiny long, narrow cones.
While aspens are best situated in full sun in moist, fertile loam with plenty of calcium, they tolerate poor soil and can withstand temporary drought. Stressed trees are particularly subject to a myriad of pests and diseases. Fall clean-up of fallen leaves is critical to reduce the spread of fungal leaf spots. Plants offered for sale may be nursery-grown or collected from the wild.
Sadly, aspen is probably not the best choice for local gardens. The same qualities that make aspens perfectly suited for colonizing mountainsides denuded by fire, rock slides and avalanches create problems in more constrained spaces. They spread aggressively by surface roots and suckers that pop up everywhere and crowd out other plants.
If you have lots of space and live above about 7,500 ft., you can try aspens in a natural setting. Understory plants might include shade-tolerant natives such as snowberry, wild roses, or Boulder raspberry. For more ideas, see Colorado University Extension’s fact sheet on Native Shrubs for Colorado Landscapes.
Article and photos by Leslie Holzmann, Colorado Master Gardener.