You can rest assure that your deer aren't hurting for anything to eat right now then. Sunflowers are tough to grow for a lot of folks because they get wiped out before they can produce. They're not overly browse tolerant either. I had them put back out after browsing last year but they were just quickly browsed again and eventually bit the dust. Give it some time. When it starts getting a little hotter and drier....and native spring forage begins to harden off...then the deer will very likely turn to the sunflowers. They may get wiped out within 5-7 days if the plot is small. Deer density is going to play a role as well.