Colorado is largely semi-arid, with low humidity, high evaporation rates, and large daily temperature swings. Elevation varies widely across the state, which affects how quickly soils dry and how trees respond to heat and drought. Many urban and suburban landscapes in Colorado have shallow, compacted soils that do not hold water well. That combination makes intentional, efficient watering essential during drought.
Trees are not small lawns. They need infrequent, deep water to keep roots alive and to maintain structural and long-term health. During drought, a tree’s tolerance depends on species, age, root health, and soil type. Knowing the basics of how much, how often, and where to water will help you protect valuable trees while conserving limited water supplies.
Water deeply, infrequently, and slowly.
Apply water so it soaks 12 to 24 inches deep for most trees. Feeder roots live primarily in the top 12 to 18 inches of soil, but roots often extend beyond the canopy. Frequent shallow watering encourages surface roots and weak drought tolerance.
Target the root zone, not the trunk. Water should reach the area at and beyond the dripline — the outer edge of the canopy — and out toward the root tips. Avoid mounding water around the trunk flare.
Reduce evaporation loss. Water early in the morning when winds are low and temperatures are cooler. That improves infiltration and reduces waste.
Monitor soil moisture. Use a long screwdriver, soil probe, or moisture meter to check moisture at several depths and distances from the trunk. Visual signs of drought stress are lagging indicators; proactive soil checks are better.
A practical rule of thumb to start with is 5 to 15 gallons of water per inch of trunk diameter per watering session for established trees. For example, a 6-inch diameter tree might receive 30 to 90 gallons per deep watering. Frequency depends on tree size, species, soil texture, and weather, but deep water every 7 to 14 days is common during hot, dry periods.
Adjust the amount for soil type:
Note: young trees use proportionally more water relative to size because they need to establish roots. Newly planted trees often require multiple waterings per week during the first growing season.
Soaker hoses and drip irrigation are the best choices for conserving water while delivering it to the root zone. They apply water slowly and can be configured to reach the entire root spread.
For drip lines:
For soaker hoses:
For new installations, test run the system and then dig a small test hole to measure the depth of wetting after a cycle. Adjust runtime to achieve the target 12-18 inch depth for most trees.
Hand-watering is possible but inefficient for large trees. Use a hose with a flow control or a slow-fill soaker bucket to reduce runoff. For small or newly planted trees, a slow trickle for 20 to 45 minutes can be sufficient.
Water early in the morning when temperatures are lower and winds are calmer. Morning watering maximizes infiltration and reduces evaporative loss.
Avoid heavy watering in the heat of midday when evaporation is highest. Avoid late-night watering if you live in a very humid microclimate where prolonged leaf wetness could promote disease; in most arid Colorado settings, evening watering is acceptable.
During winter, evergreen trees can suffer from winter desiccation when soil is dry and winds are high. Provide supplemental deep watering on warm, sunlit days when the ground is not frozen, especially before the ground freezes in late fall and during mid-winter thaws. Aim for one or two deep waterings in dry winters.
Spring and fall are critical. Watering in late summer and early fall helps trees harden off and recover before dormancy. Conversely, avoid heavy late fall watering right before hard freezes; time watering when tree tissues can absorb moisture.
Mulch conserves soil moisture, moderates soil temperature, and reduces competition from turf and weeds.
If soil is compacted, consider vertical mulching or aeration around established trees to improve infiltration. Be careful to avoid damaging major roots with mechanical aeration tools; consult an arborist for large trees.
During strict water restrictions, you may need to prioritize which trees get supplemental water.
Consider priority order:
Lower priority: well-established drought-tolerant species and trees that are already stressed beyond recovery.
Document critical trees with photos and measurements so you can justify irrigation needs if enforcement authorities request information.
Common signs of drought stress:
If symptoms are widespread, or if whole limbs are dying back, consult a certified arborist. Problems that look like drought stress can be caused by pests, disease, root damage, or soil issues. An arborist can assess root condition, soil compaction, and pest presence, and can recommend targeted treatments.
Example schedule for an established 8-inch diameter shade tree in Colorado during peak summer:
Example for sandy soil:
Newly planted tree first season:
Adjust all examples for local microclimate, wind, and recent precipitation.
By focusing on targeted, deep watering and improving soil and mulch practices, Colorado residents can protect trees through drought while conserving scarce water resources. These methods extend tree life, preserve the benefits trees provide, and reduce long-term water use compared with inefficient surface or frequent shallow watering.