How to care for trees in the high desert

By Paige Slaughter

Dear Ms. Paige,
You gave me a wonderful birthday gift when I saw your article in October’s issue.
 Where I live, rocks and stones are normal and gardening is minimal. Three and half years ago, I planted an autumn blaze maple tree and a silver maple. A few weeks ago, I purchased two 1.5-cubic foot bags of NatureScapes and spread each tree with one bag. Then, when I read your article, I think I put too much around each tree. Do I take away some of the mulch? Do I turn it each year? My water bill said last year to water every three months. Usually, I water for 3-4 minutes. Is that enough?

Sincerely, Janet

Thanks for writing in, Janet! I’m glad I had the honor of giving you a birthday gift, one gardener to another. Tree care in the high desert has been an interesting topic to research, and your questions lead my curious mind in a few different directions. I hope you enjoy this article and find my response helpful! 

Maple trees

Commonly, maple trees aren’t native to Colorado, although the Bigtooth maple grows in western canyons and on stream banks and hillsides. The silver maple is a common landscape tree but performs poorly in the heavy alkaline (high pH) clay soils of the high desert, and is often plagued by iron chlorosis—yellowing of leaves caused by iron deficiency. Autumn Blaze maple, a hybrid between red and silver maples, suffers from some iron chlorosis, too.

Mulch

As with all nutrient imbalances, you can keep your maples healthy with the right fertilizer. A soil test will help you determine what you need, though if the maple’s leaves are yellowing, it’s a sign that either the soil is too compact (and so the tree is getting overwatered) or there’s a lack of soluble nutrients— probably iron. 

Mulching with organic matter (such as weed-free straw, bark chips or shredded bark) helps to build soil, protect the tree’s roots, regulate soil temperatures throughout winter and, over time, decomposes and provides nutrients. Compost is always a good idea. You can mix it into your mulch or add a layer of compost first with a layer of mulch on top of it.

Spread the mulch out at least two feet from the trunk to create a 2-4-inch layer—do not pile it up against the trunk. Mulch around trees and other perennials gradually decomposes and doesn’t need to be turned after plants are planted and established. Renew the mulch when the layer gets thin: gently rake the decomposing layer to make way for fresh air and water, check for signs of fungal disease and see how deep the layer is before adding a thin layer of fresh mulch. 

Water

How much you water depends largely on your soil. Clay soils tend to retain water, which is why compost and organic matter are so beneficial to our high desert garden ecosystems. 

Maple trees are dormant in winter and don’t need to be watered as frequently as during their growing season, if at all, depending on snow. 

The best way to water any tree is slow and deep. Ideally, apply a slow trickle at the tree’s base for several hours rather than a more frequent, heavy, short soaking. During the growing season, you can determine whether or not to water maple trees by digging down about four inches into the soil next to the tree. If the soil is wet at this depth, do not water; if the soil is dry, water.

You can also observe the leaves. Underwatering shows up in browning or drying of leaves while overwatering can cause leaf yellowing.

Let’s talk “native plants”

Landscaping and gardening in the high desert require us to make decisions about growing plants that are not drought-tolerant. Many gardeners and agriculturalists use the term “native plant,” and place value on using them in both landscaping and food production. However, there’s little consensus on the term’s definition, and there are some nuances that are both fascinating and important.

Perhaps the most common thread is the human factor. Definitions imply or state explicitly that native plants are those “not introduced by man” or that “occur naturally” without human intervention. Often, however, these definitions are Euro-centric, explicitly or indirectly defining “native” as prior to European contact.

The reality is, humans have coevolved with plants for millions of years. The first peoples who inhabited the Americas are thought to have migrated to and throughout the Americas 17,000 years ago. According to Crow Canyon Archeological Center in Cortez, from 6,000 to 500 BC people began experimenting with growing domesticated plants, and during the Basketmaker Period (500 BC to 750 AD), people became farmers.

To classify a plant “native” solely because it was here in the late 1500s when Europeans arrived in the Mesa Verde region—after 2,000-7,000 years of coevolution with indigenous Americans—disconnects us from the complex relationships between plants and people.

The fact is, people and plants have been evolving alongside each other (that is, interacting with and responding to each other) for a very long time. It’s helpful when thinking about so-called native plants to consider the larger and deeper pictures of environment and resiliency, garden and regional ecosystems. 

So many aspects of modern living and technology can be considered invasive. Our homes, jobs and food systems can make us incredibly disconnected from the land and natural systems.

However, we’re empowered to be aware of how our world changes (as it always has) over time. We can work with new technologies and cultural shifts just like we work with a maple tree or a tomato in the high desert: with intention, curiosity and compassion. 

When we embrace the idea that we are still coevolving with plants and that we’re still a part of nature, then we can interact with our gardens and world in more profound and intimate ways. 

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