Should You Water Your Trees?

Mature Trees

Mature trees, especially older ones, develop an extensive network of roots and can survive on rainfall exclusively. Some of these roots run very deep, which is why supplemental watering is usually unnecessary. Most mature shrubs can also support themselves on rainfall alone. But during extreme conditions, even mature trees/shrubs may benefit from irrigation.

An established tree is one that is given adequate time and proper care to grow a root system that enables it to survive without irrigation. A tree’s root system can extend nearly 3 times as far as the distance from the trunk to the branch tips.

Note: the establishment and maintenance of trees depend on the species, its size at planting, soil type, drainage, and other environmental factors. Each tree has different requirements.

Watering Mature Trees

So, you have determined that your mature tree needs water:

Our recommendation: “Add water to wet the top 12 inches of soil every 2 to 4 weeks in extended drought. Apply water to all soil under the canopy if possible. This may take several hours or more depending on what type of application devices are available to you. If you have limited time to devote to your trees, we think it is better to completely wet a small area than to only wet the surface few inches over a large area.” (Trees and drought – Landscape plants – Edward F. Gilman – UF/IFAS)

Young Trees

Irrigation is necessary when young trees and shrubs are not yet established, because they don’t have the root system to survive on rainfall alone. Young trees need supplemental irrigation to support healthy growth.

Small woody trees and shrubs typically take a year to establish.
Larger woody trees take longer than a year to establish

If you have young trees in the landscape, install a drip irrigation or a bubbler to irrigate, if possible. Trees 24 months or younger should be monitored closely for signs of dehydration during extended periods of drought.

Watering Young Trees

So, you have determined that your young tree needs water:

Our Recommendation: “First, remove all mulch from on top of the root ball; mulch can prevent water penetration into the root system. Apply about 5 gallons of water per inch of trunk diameter to the top of the root ball and surrounding soil. Apply it slow enough so none runs off. Two irrigations per week will keep most trees alive; more frequent irrigation would be even better for trees planted in the last several months.” (Trees and drought – Landscape plants – Edward F. Gilman – UF/IFAS_)

It’s the Law

Reminder: All automatic irrigation systems need an operational shut-off device once a certain amount of rainfall is detected, like a rain sensor, as required by law in the state of Florida.

Florida Statute 373.62 states: “Any person who operates an automatic landscape irrigation system shall properly install, maintain, and operate technology that inhibits or interrupts operation of the system during periods of sufficient moisture”. Read more about Residential Irrigation System Rainfall Shutoff Devices, or Rain Sensors. (ABE325/AE221)

Water Restrictions

Be sure your irrigation program is complaint with water restrictions. Check your city/county for additional restrictions.

New Watering Guidelines Issued for Pasco County

Visit this resource to read more about irrigation requirements when establishing trees. For more information, visit Tree Care During Drought – Gardening Solutions.

Learn more about tree establishment irrigation research at the University of Florida.

Stay tuned. Heat Wilt vs Permanent Wilt is coming next.

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