Happy Soil, Happy Trees

The Importance of Mulch Rings for Young Trees: Removing Grass for Optimal Growth

Establishing healthy trees in urban environments can be challenging, particularly when faced with poor soil and difficult environmental conditions in Central Kansas. However, one critical practice that significantly enhances tree growth and soil health is implementing proper mulch rings around young trees and removing grass from the surrounding area of the young tree's base. Recent soil sampling efforts taken in Great Bend, Kansas, from underneath a newly established Exclamation Plane Tree and the grass immediately surrounding the mulch ring have highlighted the stark benefits of this approach.

Significant Soil Improvements

ISA Certified Arborist Jeremy Elliott recently took several soil samples at a depth of 6-8 inches from the grass surrounding the mulch ring and within the mulch ring about 3 feet away from the tree's root ball. The mulch rings had been established for 3 years, but besides adding more mulch over the last 3 years, the soil at the tree planting site has not been amended. The grass and the mulch rings have received the same type and amount of fertilizer with minimal herbicide usage over the last 3 years. The striking results provided compelling evidence of how mulch positively impacts soil quality, which is extremely important for the establishment of young trees.

Organic Matter

We observed a remarkable 134% increase in organic matter in the soil beneath the mulch ring compared to the grass-covered areas, moving from 2.3% to 5.4%. This boost in organic matter is crucial, as it enhances soil structure, improves moisture retention, and fosters a thriving community of beneficial microorganisms that support tree health and improved root development. Organic matter within the soil is arguably one of the most important factors to consider when determining soil health and can drastically enhance root cycling within the tree's root zone.

Nutrients

The soil's nutrient profile also showed significant improvements. Phosphorus levels increased by 56%. Phosphorus is vital for energy transfer and photosynthesis, driving robust root growth. We also noticed that available nitrates rose by 40%, which is crucial for vegetative growth and the overall vigor of the young tree. The increase in available nitrates is directly correlated to the improved organic matter within the soil. Potassium also increased by 28%. Potassium is essential for regulating water usage and promoting disease resistance and the tree's overall health.

Interestingly, there was very little difference in soil pH between the mulch and grass areas, indicating that the enhancement in soil quality and nutrient availability was not dependent on pH alterations. pH within the mulch ring and the grass was slightly alkaline and measured approximately 7.6.

The Negative Impact of Grass

While grass may seem like a natural choice for ground cover around trees, it can hinder your tree's root establishment. Grass competes fiercely with young trees for water and nutrients, often resulting in stressed plants that struggle to reach their full potential. Additionally, the area surrounding your tree is often overwatered to maintain the turf health that is desired, which is counterproductive to fine root hair development of young trees. Also, shallow root systems of grasses can limit tree root expansion, restricting access to crucial resources. Other studies have shown that new tree root development underneath grass is 10-15x less abundant than trees planted with a mulch ring around it.   

Moreover, traditional turf maintenance practices such as mowing can lead to soil compaction around tree bases, exacerbating issues in urban settings where soil is already compromised. We are also more likely to damage trees with weekly maintenance practices by wounding them with weed eaters and mowers hitting the base of the tree. By removing grass and replacing it with a properly maintained mulch ring, we not only eliminate competition but also create a more favorable soil environment for trees to thrive.

Conclusion

In conclusion, the benefits of installing mulch rings around young trees in urban environments cannot be overstated. Our findings illustrate that mulch significantly improves soil organic matter and nutrient content, providing critical support for tree establishment and growth. Regardless of the challenging soil conditions commonly found in areas like Central Kansas, proper planting techniques and the effective use of mulch can drastically alter the landscape of urban forestry.

By embracing mulch rings and ensuring grass removal, city planners, landscapers, and homeowners can foster environments where urban trees not only survive but flourish, contributing to improved air quality, enhanced biodiversity, and greater aesthetic value in our communities. Let’s advocate for these practices that debunk the notion that healthy trees cannot thrive in less-than-ideal soil conditions, paving the way to a greener, more resilient urban ecosystem in Central Kansas!