Be aware that Preen and other pre-emergent herbicides will kill flower and vegetable seeds, just as it does the weed seeds. For example, plants like beans, lettuce, and carrots seeds are often directly sown in the garden and may be killed.

Can you use Preen around flowers?

Preen is safe to use in flower gardens once plants are established. Label instructions suggest using the product after ornamental flowers, grasses and shrubs are at least 3 inches in height. Flower seeds sown into the garden after an application of Preen will not germinate.

What plants can you not use Preen around?

It's best to wait 12 weeks before starting seeds in soil that was treated with preen. And then you should wait until your seedlings have at least five leaves before you apply Preen again. There are some plants that aren't affected by Preen like broccoli, cauliflower, carrots, peas, celery, and radishes.