How Colorado homeowners can protect trees during dry conditions

The rain and snow Colorado picked up this week may have helped chip away at drought conditions, but tree experts say one wet stretch does not mean trees are in the clear heading into summer.

Trees across Colorado are still dealing with the effects of long-term dry conditions, and according to researchers, drought stress can create problems that go far beyond brown leaves or dry soil.

Jon Martin, a research scientist at the Urban & Community Forestry Hub at CSU Spur, studies how trees respond to urban conditions and changing climate pressures. His work includes monitoring water use in CSU Spur's research grove and identifying which species are best equipped for Colorado's future.

"When conditions are dry, trees become more susceptible to pests and diseases," Martin said. "That's something that could challenge trees in the state."

One of Colorado's most recognizable examples is the mountain pine beetle.

"Pines are trying to pitch out those pine beetles that are infesting them," Martin said. "If water is in short supply and the trees are stressed, they are less capable of doing so, and pine beetles tend to proliferate in a more pronounced way."

While homeowners may be tempted to react by adding extra water, Martin says successful tree care is not simply about watering more — it is about watering wisely.

With recent moisture falling across parts of Colorado, he says irrigation may not be necessary right now.

"It's important to irrigate when it's most appropriate," Martin said. "Right now we are getting a lot of moisture, so irrigation could be ceased or paused."

He recommends checking the soil before turning on sprinklers.

One simple method involves pushing a screwdriver or even your fingers into the soil around the tree.

"If you plunge it down and it comes out dry, you need to water," Martin said. "If it comes out pretty muddy, you know there is quite a bit of moisture down there and you can hold off."

He added that trees generally benefit from deeper, less frequent watering instead of constant watering.

Where that water goes also matters.

Many people assume the base of the trunk is where water should be concentrated, but Martin says that's a common misconception.

"The drip line is where irrigation is very helpful," he explained. "Below the tips of the branches you're going to find more absorptive roots."

Those outer roots are doing much of the work in collecting moisture and nutrients.

Mulch can also play a major role, especially during drought conditions. Martin says it helps keep moisture in the soil, lowers soil temperatures and even insulates roots during winter.

"It also provides nutrients to the soil," Martin said.

Some Colorado communities including Denver, Boulder and Littleton periodically offer free mulch programs for residents.

For homeowners planting new trees this year, Martin says drought should not necessarily stop those plans.

"I think it's still okay to plant with the current dry conditions," he said.

Young trees do need extra attention because their root systems have not fully developed.

"Thoughtful irrigation is probably the number one for success in establishing a young tree," Martin said.

As homeowners think about what to plant, Martin cautions against searching for a single "perfect" tree species.

"I think that's a pitfall — trying to identify the best tree, the number one top-performing tree," he said.

Martin says relying too heavily on one species can create a more uniform urban forest, potentially making neighborhoods more vulnerable to future pests and diseases.

Still, Martin says drought-tolerant species can play an important role. One example he pointed to is the Kentucky coffeetree, though he notes there are many suitable options you can check out on The Front Range Tree Recommendation List. 

As Colorado moves toward hotter summer months, Martin says homeowners should start with something simple: paying attention.

"I would say appreciate your trees," he said. "Notice them, watch them and appreciate what they are doing for you, your neighborhood or your community."

Because sometimes the first sign a tree needs help is simply noticing that something has changed.