Sunflowers are usually ready to be harvested beginning in mid-September and into October. Seed heads can ripen on the plant, but they will need protection from birds. Try covering the heads with a paper sack or cheesecloth once the petals start turning brown. Use a twist tie or rubber band to secure the covering. This will not only help keep birds out but will prevent ripened seeds from dropping out of the head. Check for maturity by looking for the following signs:
– Florets in the brown center of the flower disk should be shriveled.
– Heads should have turned down.
– The backside of the head should be lemon yellow.
The ultimate check, of course, is to pull a few seeds to see if they have turned black with white stripes, the typical color. Empty shells usually indicate a lack of pollination earlier in the year. If heads are to remain uncovered, harvest when a few seeds start turning black and white. The flavor will not be good as when seeds are allowed to ripen on the plants, but fewer seeds will be lost.
Cut the heads and place in a paper sack. Some people prefer to cut the heads with about a foot of stem attached and hang them upside down in a dry, well-ventilated area. A paper bag or cheesecloth can be placed over the heads to prevent seeds from dropping as they dry. Seeds can be easily removed from dry heads by rubbing gently.
Kansas State Research and Extension