What can be used to kill grass growth under pine straw?

There are several methods you can use to kill grass growth under pine straw. Here are a few options:

1. Pre-emergent herbicide: Apply a pre-emergent herbicide before the grass seeds have a chance to germinate. This will prevent new grass from growing but won't affect existing grass. You should reapply the pre-emergent herbicide according to the package instructions to maintain effectiveness.

2. Post-emergent herbicide: If grass has already started growing, you can use a post-emergent herbicide to kill it. Post-emergent herbicides are designed to kill existing grass, but they may also harm other plants, so be careful when applying them.

3. Boiling water: Pouring boiling water directly onto the grass can effectively kill it. This method is organic and doesn't require any chemicals. However, it's not practical for large areas and may damage surrounding plants if not applied carefully.

4. Vinegar: White vinegar can also be used to kill grass. Mix equal parts vinegar and water and apply it to the grass. The vinegar will scorch and kill the grass, but it's not as effective as herbicides and may need to be reapplied multiple times.

5. Physical barriers: You can also try using physical barriers to block grass growth under pine straw. This can include laying down several layers of newspaper, cardboard, or landscape fabric under the pine straw. These barriers will prevent sunlight from reaching the grass seeds, inhibiting their growth.

When using any of these methods, be sure to read and follow the instructions on the product label carefully to ensure safety and effectiveness. Additionally, consider spot-treating small areas first before applying to larger areas to ensure the desired effect and minimize any potential harm to surrounding plants.