Preen in Asparagus Bed: Which Product? Read the Label.

Preen Has Multiple Formulas—Only One Is for Vegetables

"Preen" is a brand, not a single product. For asparagus (a perennial vegetable), you need Preen Vegetable Garden Weed Preventer (corn gluten meal-based). Others contain synthetic herbicides (trifluralin, etc.) not labeled for edibles.

Check Preen's product page to match your exact need. When in doubt, use plain corn gluten meal (20 lbs/1,000 sq ft) at spear emergence—it's OMRI-listed and safe for asparagus.