Q: After this year’s rains, we have lovely moss lawn. Can you recommend a pre-emergent we could use that would be unfriendly to potential weed growth but not harm the moss?

A: Pre-emergents are chemicals that prevent seeds from germinating. Since moss reproduces by spores, theoretically a pre-emergent should keep weeds at bay while allowing moss to grow freely.

But a pre-emergent is also a “chemical” and the effect of pre-emergents on moss is mostly unknown…..although Ashton Ritchie from the Scotts Company says the label for Halts (pendimethalin) states that it can be used to control moss with a fall application.

Try other pre-emergents (click for sources) on a small section of your “lawn” in March and let me know your results in June.