Abstract: A mobile collector or harvester for weed seeds that are normally discharged onto the ground during a combining operation, is connected to trail a conventional grain combine, and collects the straw and the tailings discharged from the separating sieve that normally discharges small chaff and seeds onto the ground. The harvester frame has a conveyor for conveying straw and chaff onto a separate shaker screening member, which is of size to let the small weed seeds drop onto a grain pan and then into a hopper, while the straw is retained on the top of the screen and discharged onto the ground. A separate auger conveyor is used for elevating the weed seeds from the hopper into a storage tank, which is then periodically emptied through the use of another auger conveyor. The entire unit is self-contained including an internal combustion engine power unit, that drives a hydraulic pump for operating hydraulic motors through suitable valves.