Goatheads are invasive weeds in the West and other areas. The only way to get rid of them is to poison them periodically with glyphosate, the active ingredient in products like RoundUp. Heed all precautions - don't spray on a windy day, cover your skin and eyes, and store it in a safe place. Spray in the late afternoon or early evening - plants take in the poison on their leaves at night and the poison goes directly to their roots. Your dog won't be harmed if you keep him inside while you are spraying and overnight. Once the weeds are dead, you will have to remove them to rid your yard of their stickers. Wear thick gloves. The goatheads will have dropped seed by now, so you may have to do this again in the spring.