But if their production standards are anything to go by, then a good chunk of your seeds will see their first leaves. Preen Garden Weed Preventer blocks new weeds from germinating in your garden for up to 3 months and is labeled for use around 200 established flowers, vegetables, trees, and shrubs. Time to harvest Approximate number of weeks after germination the flower should be ready to harvest.  Source: <a href="https://estenografo.com/department-of-agriculture-noxious-weed-seed-rules/" / rel="nofollow">https://estenografo.com/department-of-agriculture-noxious-weed-seed-rules/</a>