Watering: When, How Often and How Much
Watering Trees, Shrubs, and Other Plants
How much should I water? That’s the number one question asked of horticulturists, arborists, nurseryman, and landscapers.
Answer: It depends! Specific recommendations about frequency and amount of water to apply are almost impossible to give.
Watering recommendations aren’t “one fits all”. Frequency and amount of water to apply need to be based on soil type, drainage and species involved. Temperature and length of drought may be considerations. Most importantly, is the plant well established or is it one that has been newly planted and needs more frequent watering during the establishment period?
A rule of thumb that applies to new tree establishment: It takes 1 full growing season for each inch of trunk caliper, for a tree’s root system to regenerate enough roots to survive without the need for supplemental watering.
If a minimum of 1 inch of rainfall per week is not available, supplemental watering may be needed.
A frequently sited recommendation for watering a newly planted tree is to provide 3-5 gallons of water 1-2 times per week. Tip: Clay soils drain slowly and sandy soils more quickly than good black topsoil. Adjustments may need to be made to this watering regime.
More frequent waterings directed over the top of the root ball are more beneficial than greater volumes applied infrequently. Note: Over watering can be just as harmful as underwatering.
Always check root ball soil moisture conditions before watering with a probe or hand trowel after pulling back some mulch. Especially when the tree was container grown.
I find that a 5-gallon bucket or hose with a water breaker attachment work best when watering newly planted trees. A water sprinkler placed under an established trees crown provides good overall coverage. One inch of supplemental water per week during dry periods is recommended and can be measured by placing a pan in the area being irrigated and measuring the amount of water collected.
Finally, mulching with woodchips is the best thing you can do for your trees long-term health and well-being. Mulching serves many purposes, the least of which is conserving soil moisture.