You can work Preen into the soil when you plant vegetable seeds, but you should not use Preen with flower seeds. Wait until the flower seedlings are two to three inches tall before spreading Preen around them.
About this Author
Melody Lee worked as a newspaper reporter, copywriter and editor for 5 years. In addition, she has edited magazine articles and books. Lee holds a degree in landscape design and is a Florida master gardener. She has more than 25 years of gardening experience, which includes working at nurseries and greenhouses.