Mulch rings help to promote healthy trees

K-State horticulture expert suggests organic mulch around perimeter of the tree

At a glance: Kansas State University horticulture expert Matt McKernan recommends installing a mulch ring around trees to promote healthy growth.

More information: Matt McKernan, hortsupport@ksu.edu

Aug. 25, 2026

K-State Extension news service

MANHATTAN, Kan. – Homeowners who are looking for ways to promote healthy, growing trees in their yard are well-advised to remember this axiom: A ring is a tree’s best friend.

For trees in the landscape, that means a mulch ring, says Kansas State University horticulture expert Matt McKernan. A mulch ring is a circular border surrounding the base of a tree. When planting a new tree, he recommends including a mulch ring that covers the soil beneath the tree canopy.

“Mulch rings will benefit trees of any size, however, one of the greatest benefits of using a mulch ring around trees in a lawn area is to prevent maintenance equipment from coming too close and damaging the trunk,” he said. “Also, plants grown directly beneath the tree canopy compete for water and nutrients, so a mulch ring keeps that soil covered without creating competition for the tree.”

Research from K-State has shown that newly planted trees with mulch rings around them grew 2-3 times more in the first two years of establishment than trees surrounded by turf, according to McKernan. “This little change can make a big difference in the overall growth and health of the tree.”

McKernan suggests using organic mulch, “for the same reasons it is selected for landscape beds,” he said. “Organic mulches are plant-based mulches, and will break down over time, contributing to soil health around the tree”.

Organic mulches could include wood mulch, bark mulch, shredded leaves, cottonseed hulls, or others. In addition to benefiting soil health, these mulches conserve and extend available water, protect from soil erosion, and reduce competition by suppressing weeds.

“The mulch ring around trees in a lawn should be at least 3-6 feet in diameter depending on the overall size of the tree,” McKernan said. “Ideally, the mulch ring should extend to the drip line of the tree, which means the ground beneath the entire canopy of the tree should be covered. This is not always practical, but the larger the mulch ring, the more the tree will benefit.”

The mulch ring should include a 6-12 inch diameter circle of bare soil at the center so that mulch is not right up next to the trunk, to prevent rotting and girdling roots. The mulch should be 2-4 inches deep and re-applied annually.

“If mulch is applied too deep (more than four inches), the mulch can actually restrict oxygen from the soil and negatively affect the tree’s root development,” McKernan said. “It’s also critical that mulch is never applied against the trunk or covering the root flare of the tree. In these scenarios, mulch may do more harm than good for the tree’s health.”

McKernan and his colleagues in K-State's Department of Horticulture and Natural Resources produce a weekly Horticulture Newsletter with tips for maintaining home landscapes and gardens. The newsletter is available to view online or can be delivered by email each week.

Interested persons can subscribe to the weekly newsletter, or submit their garden and yard-related questions, by sending email to hortsupport@ksu.edu. More information also is available at your local K-State Extension office. 

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K‑State Extension is a short name for the Kansas State University Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the wellbeing of Kansans. Supported by county, state, federal and private funds, the program has county extension offices statewide. Its headquarters is on the K‑State campus in Manhattan. For more information, visit https://extension.ksu.edu. K-State Extension is an equal opportunity provider and employer.