Q: I was camping in Utah last year when the aspen trees were just turning colors. Some groups of trees were yellow and others were still green, and it was a beautiful sight. I want to grow some aspens in my yard but I cannot find any in local nurseries. If I bring potted aspens back from Utah, will they grow in Thousand Oaks?

A: I too have vacationed in Utah and Colorado in the fall, and I share your affection for these beautiful trees. If there were any way they could be successfully grown in Thousand Oaks, I would love to create a grove of these trees in my yard.

Quaking aspen trees get their name because of how their leaves “quake” or flutter in the slightest breeze. The leaves are attached to their branches by very thin stems that allow them to move independently of the branch, giving the tree the appearance that the entire plant is just shaking.

These trees are usually found in the higher elevations throughout the western mountains where the soil is moist, welldrained and full of nutrients. They thrive in a climate where the nights are cool and the winters are cold. They don’t mind heat during the day, but they want to cool down at night. That’s putting it simply, but the fact is they just don’t do well in the mild climate that we have in the Southern California coastal areas.

The really interesting fact about this species of tree is that it propagates by cloning. As the roots of the tree spread out, suckers sprout off the roots and make new stems, or trunks, in what appear to be new trees. These new stems that sprout off a common root system are really not individual trees at all but actually new members of a colony. Each new stem of the colony continues to send out roots, so more and more stems are created. Each stem looks like a new individual tree, but in fact it is an identical clone of the same sex as all the other trees in the colony.

There is a quaking aspen colony in the Fishlake National Forest in Utah that has more than 45,000 stems all thought to be sharing the same massive root system. Many scientists believe this single colony, which they’ve named Pando, may be the oldest living organism in the world, with a continuous root age of 80,000 years old. Although each stem of the colony lives for only about 100 years and dies off, it is replaced by a new stem that sprouts from the gigantic root structure that continues the life of the colony.

Each stem in a colony begins to change leaf color at the same time and each colony according to its own timing. But all colonies of aspens will begin to change leaf color in the last two weeks in September through early October. It is because of this colonial system that you can look at a mountainside in late September and see large groups of aspen trees, each group in different stages of leaf coloration. Understanding how and why this all takes place can add that much more to the experience of being in the high mountains in early fall.

I agree with you: I wish quaking aspens would flourish in Thousand Oaks because they are just cool trees.

David D. Mortimer is a certified arborist with more than 30 years’ experience in the tree care industry. E-mail questions to dmortimer@theacorn.com.