5 Watering Your Cannabis Seedling. 40 products. Note Never use a non-selective weed killer on your new lawn, no matter how mature the grass looks, as it will kill all plants it comes into contact with including the grass. Source: http://maxxtaxglobal.com/2013/06/17/a-research-of-the-passage-of-weed-seeds-by-way-of-the-digestive-tract-of-the-chicken/