Are You Overwatering Your Mature Tree? Smart Watering Tips for Established Trees

Most homeowners assume that trees need lots of water to stay healthy. While that may be true for trees during drought periods, or young and newly planted trees, established trees getting normal rainfall are a different case.

Mature trees have extensive root systems that tap into water stored deeply in the soil. Too much water can lead to root rot, disease, and shallow root growth near the surface of the soil.

Knowing how to spot signs of overwatering trees, and how to water established trees properly will help lengthen the life of the green giant in your yard while developing its resilience.

Signs You Might Be Overwatering a Mature Tree

Overwatering and drought stress symptoms can look similar. Make sure to do a moisture test on your soil before adjusting your watering technique. Here are some signs of overwatering mature trees:

• Yellowing leaves during the spring and summer
• Fungal growth at the base of the tree or  above the roots
• Consistently soggy soil or standing water around the trees
• Algae growing on the soil or root surfaces
• Foliage wilting or curling despite regular watering
• Leaf drop during wet periods

If you’re spotting these symptoms despite regular watering, there’s a good chance you’re actually overwatering your trees. Saturating soil in the root zone with water for extended periods suffocates roots due to lack of oxygen while inviting root diseases.

How Mature Tree Watering Should Work

Mature trees only need watering during extended dry periods. Water should reach the deep roots, not just the surface. It takes the equivalent of at least 2” of rain, or 1.25 gallons of water per square foot to begin to wet the entire depth of the root zone.

To make sure you’re not making any tree watering mistakes, allow the soil to drain well and dry somewhat between deep waterings, and use a slow soaking method instead of frequent, shallow watering. You want all of the standing water to have drained completely from the soil, but you do not want the soil to get to the point where it is dusty dry. 

Watering also depends on several variables, including the species and soil type in your yard, as well as the region in which you live.

• Clay – Clay soils retain the most water, but infiltrate and drain water, and dry out slowly. Water these with the most water, but much less frequently. Example: 3” once per month. 
• Sand – Sand soils retain the least water, and drain and dry out quickly. Water these with the least water volume, but more frequently. Example: 1” once per week.
• Silt and Loam – Silt and loam soils have intermediate properties and can be watered with intermediate volumes and intensities. Example: 2” once every 2 weeks.  
• West – Focus on drought-resistant practices and species. Tree basins and swales can help capture water, reduce runoff, and ensure deep, efficient irrigation.
• South – Ensure adequate site drainage and avoid over-irrigation from turf systems. Try using smart irrigation practices, such as consistent soil moisture testing. Allow for soils to dry between summer rains by turning off irrigation when possible. 
• Midwest/Northeast – Beware of overwatering during wet springs. Most healthy mature trees will receive enough water from rainfall.

Tools & Techniques to Prevent Overwatering

The best way to water large trees isn’t just how often you’re watering and how much water you’re using. There are several ways to ensure your tree is properly watered.

• Mulch helps retain the right moisture levels. Be sure to avoid volcano mulching when applying it! 2-3 inches thick of wood-based mulch  are ideal. 
• Slow-drip irrigation works best for long soaks when needed. Design a system with at least one drip point per square foot under the canopy of the tree. 
• Adjust your irrigation systems. Trees aren’t usually on the same watering schedule as lawns, needing more water per dose, but needing it much less frequently. Separate their irrigation zones and program them accordingly.
• Vertical Mulching Backfilling deep, vertical holes with biochar can improve drainage and allow for deeper rooting, giving you more flexibility with watering and more tree resilience. 
• Perforated Pipe / Sight Tube allows you to see when there is standing water in the soil and no need for more watering, and to pump-out excess water when needed. 

Why You Should Hire a Professional Arborist

Professional arborists are experts in proper tree care. If you notice signs of decline despite watering, you are unsure if there’s enough drainage, your mature tree is planted in a compacted or urban site, or you suspect root rot, contact your local certified arborist.

LEARN MORE ABOUT MATURE TREE CARE