Its interesting because Burlap is used mainly for garden uses. When do gardens start to see the most attention in the spring and summer. According to what they have said on the show the killings or the dumping of the bodies occurs from post memorial day through the summer. Maybe the killer has some association with a gardening company or nursery in the area.
Rbbm.
It may even be that it is not so much about the perp. having an association with a gardening company or nursery, but since those companies are active at that time, he can operate without standing out? imo.