Most sunflowers have a least a 90 day maturity period. A planting this late is pushing it for early September dove openers. However, it you are not worried about them being ready the first of September, there is still time. Sunflowers are not as easy as soybeans. Doves like a clean ground. It can be difficult to keep the ground clean as opposed to planting roundup ready soybeans. But, if you are just as interested in pheasants and quail - a weedy field might be the best thing. Sunflowers also like nitrogen. Depending on your ground, you may want to hit them with 40 or 50 lbs nitrogen per acre after they are a month old. If you want to keep them half way clean, a pre-emergent before planting and a grass specific herbicide over the top when they are three or four weeks old will help. If you are planting a mix with millet or milo, no grass specific herbicide.