Growing Aspens in Colorado

Aspen Trees

Aspen Trees

High in the Rocky Mountains of Colorado one can find an abundance of Quacking Aspen trees. With their brilliant white bark and green leaves in the spring turning to golden yellow in the Autumn, their beauty is a magnet for visitors from allow around the world.

So if you’re a homeowner in Colorado and want the same beauty to gaze upon from the comforts of your home, there are a few things to keep in mind. Many homeowners hate them for the few reasons listed below. Here are some thing to keep in mind:

The cons:

    • Expansive root system that will grow everywhere, and fast.
    • Roots will spread a hundred feet from the main tree invading lawns, driveways, landscaping, etc.
    • New trees will sprout from the spreading roots. If left alone, you’ll have a grove of Aspens.
    • Susceptible to disease and fungus. Oystershell scale and Marssonina fungus are common.
    • Doesn’t like a lot of heat. Better at high altitudes, but will work lower.

The Pros:

    • Fast growing tree that can offer a good amount of shade.
    • Beautiful spring a fall colors.
    • Does extremely well at high altitudes, those above 7,000 feet.
    • Not too difficult to care for.
    • Moderately tolerant of droughts, though more susceptible to disease and fungus if open bark wounds.

Ok, so if you’re still interested in growing Aspens in your yard, here’s what you need to to:

Planting

Aspens do best in well-drained and non-compact soils, but can tolerate other soil types as well (just not clay or sand). Plant your Aspen in the Spring. This will give the roots plenty of time to establish themselves. Dig the hole twice as wide as the root ball and back fill with 50/50 native soil and some sort of soil amendment. This will help retain moisture and promote good root growth. They like full sun, so make sure you put them someplace that gets 6+ hours of direct sunlight per day.

Watering

Keep the soil moist for the first 6 months. On really hot days, you might want to water a couple times a day to prevent the roots from drying out. When Autumn comes around, water less frequently, especially after the leaves have fallen. Let the first couple inches of soil dry out. It the winter, water once a month on days over 45°F. After the first year, you can water every other day in the summer. After about 3 years, they can handle longer stretches without water, but are more prone to disease. They do not like prolonged exposure to heat, which is why they do best at high altitudes where the temperatures are on the cooler side.

Pruning

After about 4 years, you’ll want to start shaping the tree. In the winter, cut back the lower branches all the way to the trunk. this will make the tree grow taller. Remove any diseased branches and don’t let it sit on the ground. If two large branches are rubbing against each other, remove one to prevent damage to the tree bark. Aspens are fairly hardy, but if neglected, they can get into trouble pretty quick.

Disease and Fungus

Oystershell Scale

Oystershell Scale

I’ve had problems with oystershell scale several times. This insect leaves behind a bumpy shell that’s about 5mm in size. If left untreated, this can kill the tree. There is a treatment you can mix with water and pour around the trunk base. The roots will absorb the treatment, and when the insect feeds on the tree it will die. You might need to gently brush off the scale the following year. There’s also an oil based spray for both dormant and active insect periods, but it’s a tough to apply on tall trees.

There is also a spray for the Marssonina fungus. Although the fungus won’t kill the tree, it does make the leaves look ugly. It’ll also cause them to drop early. The toughest part about the fungus is, you need to remove the dead leaves from the area, otherwise the fungus will come back the following year. However, if the tree has the right amount of water, this shouldn’t be a problem as it will naturally fight off the fungus.

Fertilizer

If you want, you can apply slow-release all-purpose fertilizer granules once in the spring time, but it’s not necessary.