The best way to get ahead and stay ahead of garden weeds is to stop them when they’re seeds. If you stop weed seeds from sprouting, they never grow and you won’t have to pull them. Different weed seeds germinate at different times throughout the growing season: spring, summer, fall or even winter, too, in some areas. For gardeners, this can mean wave after wave of new weeds. So, while early spring is an optimal time to begin applying Preen, any time is a good time to launch a weed prevention campaign.