What to Use to Kill Grass Around Trees

Pre-Emergent Herbicides

• Pre-emergent herbicides work to prevent grass seeds from germinating. When applied right before the soil favors grass seed germination, they can kill off grass. This herbicide works by creating a barrier in the soil that kills grass as soon as it emerges from its seed. Herbicides that contain bensulide, benefin, oxadiazon and siduron prevent grass germination without harming trees, according to the Journal of Arboriculture. Spray pre-emergent herbicides in the early spring and fall to prevent warm or cool season grass from growing around trees.

Post-Emergent Herbicides

• Post-emergent herbicides work on existing grass. These herbicides work by absorbing into grass foliage and disrupting the plant's ability to grow roots, produce proteins or photosynthesize. Gardeners may use a post-emergent herbicide that contains organic arsonates such as calcium acid methylarsonate, monosodium methylarsonate or disodium methylarsonate, according to the Journal of Arboriculture. You can apply these herbicides on top of trees' root systems without causing damage to the tree. However, these post-emergent sprays should be used carefully when sprayed around your preferred turfgrass.

Hand Pulling and Digging

• Removing grass by hand pulling or digging offers immediate results without using chemicals. It is important for gardeners to remove the entire root system of the plants. Grass can grow back when root fragments are left in the soil. To help you remove the entire root system, water the grass area to soften the soil. Press a shovel 2 to 3 inches from the base of the grass and at a depth of 6 inches. Push the entire root system through the soil.

Mulching

• Mulch not only prevents grass seeds from germinating, but it also helps conserve soil moisture. There is a wide variety of mulch types that gardeners use, but they are broken into two main categories: Organic and Synthetic. Organic mulch types include pine needles, pine bark, hay, compost, or wood chips. Synthetic mulch types consist of landscaping fabric, crushed brick, sea glass, gravel or stone. When mulching around your tree, avoid allowing the mulching material to touch the bark. Allow several inches of exposed soil near the base to prevent diseases or other pests from living next to the tree.