Will fresh grass clippings hurt tomato plants?

Fresh grass clippings can hurt tomato plants. They contain high levels of nitrogen and carbon which make the soil too acidic. This can lead to a condition called blossom end rot. Blossom end rot causes tomatoes to develop black spots on the bottom and then rot.

Also, grass clippings often contain weed seeds and plant diseases that can be harmful to tomato plants. To avoid these problems, compost grass clippings before using them as mulch around tomato plants or discard the clippings and use other mulch material.