You are talking about a variety of different sunflowers in size and color which are to all be ready to cut at the same time and all to be fresh as a daisy for a specific day. I think that this is a very difficult if not impossible thing to do.You are leaving too much to chance.

Hi Lian and welcome to GoY! you are going to have a huge number of stresses in the run up to your wedding and trying to grow flowers for your bouquet and table decorations is one you do not need! Given your wedding is past mid October I would suggest you use a commercial florist. Might seem costly but you then know you will have exactly what you want at your wedding and - more importantly - you will not have the stress of dealing with!

That date is rather late for sunflowers. Had you thought of using rudbeckias instead? They look pretty much the same and flower well into the autumn. They are perennials though, not annuals so you would have to get plants rather than seeds and they probably wouldn't flower first season unless you were able to buy mature plants..

When you are working toward a particular date its always dodgy because of growing conditions and weather. you would be a lot safer entrusting it to a florist.

Oops Moongrower, we crossed, but the advice is the same.