Answer: Pre-emergents must be applied before the weed seeds germinate in the spring. To stop crabgrass, for example, the material should be applied just before the forsythia blooms in the spring. There will also be a need for a later application to catch seeds that would germinate during warmer weather and at warmer soil temperatures, or if the soil surface has been disturbed. If using corn gluten, for instance, you might apply it again in about 8 weeks. For other commercial products, read and follow the label instructions carefully.
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