Miracle Gro is OK but Jacks’ Blossom Booster is better for more flowers.  Use it every 2 weeks.   No matter what you use, you’ll never be able to duplicate the look they get at the track.  Those planters are started very early and grown along all winter and spring in greenhouses and then brought out in summer a month or so before the track opens.  They are lavished with care throughout the growing season as well.  Without large greenhouses, you’ll never match their displays…just something else that is special about Saratoga.