Mammoth series mums were developed by the University of Minnesota to withstand cold weather without lifting, pruning, or even much winterizing. Mammoth mums are a low maintenance dream! To take care of your Mammoth mums, give them the best start possible by getting them into the ground in springtime. Mammoth mums need a bit of time before the cold sets in to establish a firm root system, so pop them into your garden, at the same level in which they were potted, as soon as they arrive. In most locations, that means you'll be planting in March or early April. Choose a well-draining location with full sun -- these aren't shade plants, and they don't care for puddles or pooling water. Mammoth mums live up to their name: these plants grow to three to four feet across, so make sure to space them out appropriately. Remember that Mammoth mums perform best when allowed to keep their foliage through winter, so choose a location where you'll appreciate the added wintertime height! Fertilize your mum plants with a balanced fertilizer in the spring and summer, and water them generously throughout their growing season. Fertilize for the last time in early August, or whenever fall buds begin to form. In the fall, there's little left to do -- sit back and enjoy your beautiful, HUGE mum flowers! After they've finished blooming for the season, you don't need to deadhead or cut back your Mammoth mums. They'll perform best if allowed to retain their foliage until spring. When springtime rolls around, cut off the browned foliage and branches back to the crown of the plant. Mammoth mums do require dividing every three to four years.