When is it time to harvest black oil sunflowers?

Black oil sunflowers are typically ready for harvest when the seed heads turn yellow and the back of the heads become brown and dry. The seeds should also be firm and plump, and the moisture content should be around 10-12%. Harvesting is usually done in late summer to early fall, depending on the planting date and climate conditions. It's best to harvest before the seeds start to fall out of the heads to minimize loss.