According to Preen.com, Preen Weed Preventer can be incorporated into the soil when sowing vegetable seeds. It should not be used on flower seeds. If you want to use it in your flower garden, wait until the plants have germinated and are two to three inches tall.
About this Author
Aileen Clarkson has been an award-winning editor and reporter for more than 20 years, earning three awards from the Society of Professional Journalists. She has worked for several newspapers, including "The Washington Post" and "The Charlotte Observer." Clarkson earned a Bachelor of Arts in journalism from the University of Florida.