Question: Can I plant grass over soil where a newly removed stump was ground out?
Answer: We generally don’t want to plant new trees or turf immediately over the top of existing stumps in landscapes. The reasoning is a bit complicated but somewhat simple. The stump location will have limited soil and rooting depth for nutrient uptake and structural stability due to its remaining below ground mass.
The woody debris material created from stump grinding has a high carbon to nitrogen (C:N) ratio. This reduces nitrogen availability for the new tree or grass. Also, there will be significant settling of the ground below the stump as it decays and loses its structural fiber. The soil should be added to replace the below ground roots and stump. It can take several years to fully decompose the stump unless it was ground very deeply or removed with an excavation machine.
The recommendations are adding soil to the stump area, and a little additional soil mounded to compensate for some decay. Plant the grass, preferably sod, however, seed can work, to adequately cover the newly exposed area. Be sure to add slow-release turf fertilizer to compensate for the high C:N ratio that will be robbing nutrition from the newly installed turf. Maintain adequate moisture and look for signs of yellowing, indicating low nitrogen levels.
Also, sprouts may be generated due to the roots acting as energy storage for the tree. Simply treat them with typical lawn herbicide as needed at the label recommended rates.
Fundamentals of Turfgrass Management, The Education Store, Purdue Extension Resource Center
Taking Care of Your Yard: Homeowner’s Essential Guide to Lawns, Trees, Shrubs, and Garden Flowers, The Education Store, Purdue Extension Resource Center
Homeowner Conservation Practices to Protect Water Quality, Purdue Rainscaping, Purdue Extension Resource Center
Planting Your Tree Part 1: Choosing Your Tree, Purdue Extension YouTube Channel
Purdue Landscape Report
Lindsey Purcell, Chapter Executive Director
Indiana Arborist Association