The active ingredient in Preen is trifluralin. It is a suspected carcinogen, and is toxic to fish and aquatic life, and earthworms.

Is Preen dangerous to humans?

The active ingredient in Preen Garden Weed Preventer, Weed Preventer Plus Plant Food and Preen Mulch Plus is trifluralin, used to control broadleaf weeds. Although rated as having low toxicity to humans, this herbicide is highly toxic to aquatic wildlife and should not be applied so heavily that runoff occurs.

Is Preen safe?

Preen Natural Vegetable Garden Weed Preventer offers completely natural weed prevention and is safe for use around children and pets. ... Preen Natural Vegetable Garden Weed Preventer is safe for use around established vegetables, herbs, fruits, annuals, perennials and other plants.