Steven from Yukon writes
Pre-emergent weed products like Princep usually need to be applied when soil temperatures are lower than 55-65 degrees Fahrenheit. After the weed seeds have warmed up, they germinate, rendering pre-emergent applications useless. If you are past this point, post-emergent weed control applications will need to be used. For the best timing apply pre-emergent in your specific location, we recommend contacting your local cooperative extension office.
Answer last updated on: 09/26/2018
