Preen is used as a weed preventer, and is manufactured by the Lebanon Seaboard Corporation, a company which has been making lawn and garden products since 1947. Applying Preen to flower beds, garden beds and the areas around trees and shrubs keeps weeds from germinating, saving gardeners and landscapers time spent on tedious manual weeding. Preventing weeds with Preen also keeps soil nourishment from being stolen from your plants by competing weed growth. There are a few different varieties of Preen, including a corn gluten-based organic variety which can be safely used around garden vegetables.
It's best to use Preen during the spring and summer growing seasons, after blooming plants have already begun to grow. Gardeners who want more thorough weed control for the entirety of the growing season can opt to apply Preen three times during the year: in early spring, early summer, and early fall. The plants around which you'll be applying Preen should already be 2 to 3 inches tall at the time of application. Scatter about one ounce of Preen for every ten square feet of area, making sure to apply a light and even coating. The key to using Preen successfully is to get to the weeds while they are in still seed form and keep them down wih regular re-sprinklings. Preen won't kill existing weeds. Keep any Preen particles away from your plants to prevent damage.
If you're going to lay down mulch in addition to Preen, apply the Preen after the mulch has been laid down. Sprinkle it on top of the fresh mulch and work it down and through the mulch layer by watering it. Watering and rain exposure will not dilute or wash away Preen, but repeat applications are nonetheless recommended every nine to twelve weeks.