- Both carrot and onion seeds ripen slowly and the seed heads have a tendency to shatter so you will need to either keep these bagged or to watch them closely and harvest promptly. Carrot seed heads will turn brown in early fall and you should harvest when the topmost heads are ready. Onion seed heads will dry out somewhat and you should begin to see the black seeds 'peaking' out just before the head shatters. Dry both out in the Sun and then rub the seeds to remove the flower material. Sift or carefully winnow the chaff.
All my book says about beet seeds to harvest them by cutting the plant to ground and hang the stalks upside down in a well ventilated area. You then strip the seeds from the stalk by hand and winnow out any chaff. I'm not sure about the time to do this so I salvaged a small piece of wind-damaged stalk and allowed it to dry out. I have it in the freezer now and will soon be testing the germination.- Roger