How to Grow and Care for Quaking Aspen Tree

The quaking aspen is a tree named so because its flattened leafstalks tremble at the slightest breeze. Its 3-inch-wide leaves are finely toothed and they turn a brilliant golden-yellow color in the fall. The tree is also easily identified by its smooth, light-colored bark, interrupted at intervals by darker knots and horizontal scars. Quaking aspen grows best in full sun, and average soil, and thrives in cooler regions.

Quaking Aspen Tree Care

Here are the basic requirements to successfully grow the high-maintenance quaking aspen tree.

• Grow a single quaking aspen as a specimen plant or shade tree in a large, isolated part of your property away from foundations and septic systems.
  
• Plant in average to rich soil.
• Prune this tree in the winter.

Light

Grow quaking aspen tree in full sun for best results, although it does tolerate some shade.

Soil

Provide quaking aspen with good drainage. An average garden loam is sufficient.

Water

For best results, keep the soil evenly moist. A quaking aspen should get a deep watering every two to four weeks. During hot summers, it should have water at least every other week. In winter, the tree needs water at least once a month if snow isn't already on the ground.

Temperature and Humidity

Quaking aspen is cold-hardy all the way to zone 1. The tree will not handle heat and humidity well. It is not suited to regions such as the American Southeast.

Fertilizer

Quaking aspen performs best in moderately rich soil. Fertilize it with a complete fertilizer in early spring for an extra boost. Follow the instructions on the fertilizer package precisely. The instructions will spell out how much fertilizer to use, which varies according to tree size. Over-fertilizing can burn your plant.

Types of Aspen (Poplar) Trees

There are several trees in the Populus genus. They are commonly referred to 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): This columnar tree is often planted along property borders, but it does produce suckers.
• White poplar (Populus alba): Although Populus tremuloides is 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.
  

Pruning

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 must be pruned after heavy winter snowfalls have damaged limbs. 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 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, with distinct male and female colonies. Because quaking aspen trees propagate readily through their root systems, you can take advantage of this fact to acquire new trees. This is by far the easiest way to propagate quaking aspen. Take these easy steps:

1. Simply dig up offshoots from the original tree.
2. Transplant them to a suitable location in your landscape.
3. Water regularly until established.

How to Grow Quaking Aspen Tree From Seed

You can also grow it from seed, but it's more troublesome. 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 much different from the seed-bearing female ones (both produce catkins).

Once your seeds arrive, take these steps:

1. Fill a planting container with moistened seed-starting medium.
2. Sow the seeds right on top of the seed-starting medium; don't cover them with soil.
3. Keep the medium moist; placing the container in a plastic bag will help trap moisture. Seeds will germinate in 24 hours.
4. Place the container in a window for light.
5. Plant outdoors after all danger of frost has passed.

Common Pests & Plant Diseases

Quaking aspen is susceptible to infestations of poplar borers. The larvae 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 ensuring its light levels, irrigation, and drainage, are adequate.

Quaking aspen can be attacked by powdery mildew disease. Quaking aspen likes evenly moist soil, but you must strike the right balance between dry and soggy soil. Soggy soil invites fungal infections. Likewise, don't get the leaves wet when watering. 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.

Common Problems With Quaking Aspen Tree

Quaking aspen is a very high-maintenance tree. Stay aware of these signs that indicate the tree may be in trouble.

Browsing Animals

Quaking aspens are a favorite food source for deer and elk. The animals seriously damage aspen trees by eating the shoots of young suckering trees and they eat the bark. Deer and elk also rub their antlers against the bark causing deep gashes that can kill the tree. The most significant damage occurs during mating season (September to November).

To reduce tree damage, use strong barrier fencing to keep animals out. You can also wrap bark in rigid plastic, reducing damage, although a large elk can still damage or destroy a wrapped tree. Remove all wraps in the spring.

Leaves a Mess

Quaking aspens are among the prettiest trees but are also messy in terms of their maintenance. You must continuously remove the suckers or new shoots from their spreading root system.

Bark Discolored or Falling Off

Sunscald can cause a quaking aspen's bark to become discolored, crack, fall off, or sink into the trunk. This condition occurs during winters with freezing weather dotted with unseasonably warm days. The warmth might confuse the tree, thinking it should come out of dormancy and prepare for spring growth. However, when the cold returns in full force in a few days, the tree isn't dormant and prepared to handle the cold properly.

If your area experiences winters with frequent unseasonable warm snaps, consider painting the trunk with white latex paint to deflect sun rays. Also, make sure your aspens are receiving ample water. Drought-stressed trees are more likely to suffer from sunscald. If your tree has already been damaged from sunscald, do not paint the damaged bark sections. Allow it to heal.

Browning of Leaves

Browning leaves can be a sign of aspen leaf scorch, caused by aspens not getting enough water during hot and dry periods. There's no quick fix or cure. Maintaining a watering schedule is the best way to bring your tree back to health. During the growing season, these trees need infrequent but deep watering. In the winter, ensure these trees get a deep soaking at least once a month (if no snow is on the ground).

Pale Yellow or Light Green Leaves

Your soil might have an iron deficiency if green leaves start turning pale green or yellow unseasonably soon, like in the summer. This condition is called chlorosis. You might notice the yellowing beginning at the edge of the leaves and then moving to the center. The leaf edges may turn brown, start curling, or fall off. If it's an iron deficiency, the tree could benefit from chelated iron deep root injections into the soil around the tree. In extreme cases, injections into the tree might be needed.