RECIPE #19 HOUSEPLANTS Categories: Houseplants, Fertilizer For houseplants I just mix up 1 pkg. of knox gelatin to a 2 qt pitcher and then water my plants as usual..Once a month is enough for this.. I find it works great on plants that have decided not to grow on their regular schedule to get started as well...It allows air pockets within the soil and then makes the plants grow. -----