The folks in past just marked the spot and kept hitting all the spots they see where they seeded out
since you missed keep looking, ther may be some late ones ya just have to look for the shoots, northern Nebraska was lousey with wild asparagus, what helps is print a Google map of your area and drive round and mark the ferns, next spring get a jump, the townies used to come out to the rural areas and pick, just ask the farmer/rancher if its ok to look, most folks dont care if they know what your doing and not destroying anything. Happy Hunting!