At the Forest Of Hope, take all your Leaf and Bud Pikmin. From Olimar's ship, go forward, then go left to find patches of grass. Use your C-STICK to lead them into the grass and they will start pulling it out. After a few seconds they’ll pull up yellow globs that instantly turns them into Flower Pikmin. Only the Pikmin that drink the yellow substance will turn into flowers. The yellow dew is useless if your Pikmin already have flowers. Be sure not to waste it by letting any Flower Pikmin have any. The yellow dew will appear once per day and works on any color Pikmin.