Id say 2-3 wks minimum - when does it get Cold Iowa? When's your first Frost? if you can make it to 2nd/3rd week of October, she'll pack on the weight, I'm in Minnesota, I pray I can go to 10th Oct., mine are a little further along than yours, my Pistils are turning, I Crossed a Blueberry Slushy Auto with a Sunday Driver Photoperiod creating a fast flowering Photoperiod (fast Finisher.? we'll see) were all in the same boat in the upper northwest, trying to bring in Our Crops before the snow flies !! -good luck