Q: Will a hurricane downpour after I apply pre-emergent wash the chemical away?
A: Pre-emergent chemicals dissolve pretty quickly. This means that even if you have a big downpour after applying, the first half-inch of rain dissolves the chemical and spreads it rapidly into the soil. Once the chemical is bound to the soil particles, it doesn’t move with additional rainfall. The only time it might move is if it’s applied on a steep slope and the soil and pre-emergent wash away together.