I think you have to look under purchase seeds for the rare packet, not purchase seasonal seeds. There is more than one menu for seeds! You can also buy them in build/buy mode - and use it to see what is locked/unlocked. I too miss real plantsims - I even had a mod for the TS2 ones so that any light would give them sunlight...which is slightly more accurate with today's technology lol. TS2 plantsim babies started as toddlers and went right to adults too, unless you cured them for childhood and teen years.