preen is a surface application

arent your bulbs going 6 to 8 inches down???

just scrap back the preen.. dig hole.. insert bulb... move on ...

what are late lily???

arent they supposed to be planted in oct or so ... or are they late because you forgot last oct???

what plant are we talking about... might make a difference

ken

Preen works on emerging seeds. Unless you are planting seeds, you don't need to worry.

Ditto Ken & nhbabs - Preen is a pre-emergent* weed seed application that doesn't work on weeds that have already germinated from seed or spread via runners or roots. Assuming you're planting bulbs, it shouldn't affect the growth of your lilies. Since it's a petroleum-based product, its environmental impact & consequences is an entirely separate discussion.

* prior to seeds sprouting