Why Water Matters: The Hidden Life of Trees

Written By Zac Giammarrusco

At Wild Man’s Tree Service, we love trees not just for their beauty—but for their brilliance. Trees are living systems, and water is their lifeblood. But did you know that water is also the single most limiting ecological factor in a tree’s growth and survival?

Despite water covering 71% of Earth’s surface, only 3% is usable for growing crops and trees. That tiny fraction determines whether your tree thrives—or slowly declines.

How Trees Use Water

Trees rely on water for every major biological function: photosynthesis, respiration, and transpiration. But here’s the kicker—less than 5% of the water a tree absorbs actually stays in the plant to build wood, leaves, or roots.

The rest? It moves.

Water travels up from the soil through the roots and evaporates from the tiny pores on the undersides of leaves in a process called transpiration. This is how trees:

  • Cool their leaves (especially in summer)

  • Move nutrients upward

  • Exchange oxygen and carbon dioxide with the atmosphere

  • And yes—make oxygen for all of us

Different species move water at different speeds. For example:

  • Red oaks: 92 ft/hr

  • Basswood trees: 11 ft/hr

  • Pines: 6 ft/hr

Each day, a mature tree can use between 10 and 150 gallons of water!


Evapotranspiration: Nature’s Cooling System

Beyond transpiration, trees also help manage stormwater. During rainstorms, leaves, branches, and bark intercept water and allow some of it to evaporate before it even hits the ground. Together, these two processes—transpiration and evaporation—are known as evapotranspiration, and they’re crucial for:

  • Reducing stormwater runoff

  • Regulating temperature

  • Improving local air quality

Drought Stress Is Real

If your area has gone a week or more without at least an inch of rain, it’s time to help your trees out. Why?

Because without enough moisture in the soil, roots can't pull in water. This leads to:

  • Wilting

  • Early fall color

  • Leaf scorch

  • Long-term decline

A good rule of thumb? 10 to 20 gallons of water per tree, per week during dry spells.

A Final Word from Wild Man

It’s easy to overlook the role water plays in tree health. But as arborists, we see the signs of dehydration all the time, especially during hot Colorado summers. So take a moment. Look at your trees. Have we had enough rain? If not, grab a hose and give them a good soak. It’s one of the best investments you can make in your landscape. And if you're unsure whether your trees are stressed or need help with watering plans, deep root feeding, or long-term drought management, Wild Man’s Tree Service is here to help.

Let’s keep your trees healthy, hydrated, and happy.

Zac Giammarrusco
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