Huge shade trees are what every Nevadan homeowner wants for summer cooling and aesthetics. However, mature trees, such as silver maples, can have shallow roots close to the soil surface that prevent grass from growing. When thin lawns happen under trees, what can a homeowner do to make the site attractive again? It may be time to remove the lawn and put in shade-tolerant plants.
Early blooming, spring-flowering bulbs are good alternatives to lawn under a tree, because they bloom before the tree leafs out. These could be mixed with shade-tolerant ground covers or shade-tolerant perennials. Perennial plants work better than annuals, because they are planted once rather than yearly, which minimizes tree root disturbance . Whatever your choice, select small plants that can be planted easily in the spaces between the roots.
To under-plant, determine the size and shape of the area you want to change and mark the perimeter. Water the area well the day before to make digging easier. Dig out the existing lawn gently so you don't damage tree roots. Spraying the grass with a grass-selective herbicide and letting it die first may simplify the removal process. Avoid cutting roots 2 inches or larger in diameter when digging. Cutting smaller roots will not harm the tree.
Keep the existing grade and don't add soil to cover the roots. Added soil can reduce water and airflow to the roots, suffocating the tree. You can add organic mulch 4 to 6 inches in depth, but keep mulch 12 to 18 inches away from the tree's trunk.
Put a bit of slow-release fertilizer, or, in the case of bulbs, bulb food in the hole according to label directions prior to planting. After planting, water all the plants thoroughly. Keep plants at least 12 to 18 inches away from the trunk of the tree.
The tree's roots are where the lawn was because that's where the water was. Maintain sufficient irrigation to the existing root system of the tree by running drippers to all new perennials or ground cover plants, irrigating the entire old lawn area with sprinklers or adding weekly supplemental deep irrigation during the hottest times of the year over the old lawn area.
JoAnne Skelly is the Carson City/Storey County Extension educator for University of Nevada Cooperative Extension and may be reached at firstname.lastname@example.org or 887-2252.