Germanicas, better known as bearded irises (Iris germanica), are perennial plants that are hardy in United States Department of Agriculture plant hardiness zones 3 to 10. They grow from underground root structures called rhizomes and are best planted in July, August or September. This early planting helps them become established and more ready for winter weather. However, you can still plant germanicas later in the fall, if necessary. Germanicas will bloom the next year in the spring and depending on the variety may bloom throughout the summer.
Turn over the top 6 inches of soil with a hoe, tiller or garden rake, and incorporate about 2 inches of organic matter, such as compost (avoid manure). Also, mix in a ½ pound of fertilizer labeled 5-10-10 (or similar low-nitrogen fertilizer) for every 50 square feet of garden space.
Dig holes that are just as deep as the germanica's rhizomes but twice as wide. Plant individual rhizomes about 8 inches apart from one another. You can also plant clumps of rhizomes that have not been divided in one spot, but when you plant them, point the tips facing outward in different directions. These clumps should be spaced about 18 inches apart from other clumps.
Form a mound in the middle of each hole. Then place the rhizome (or clump of undivided rhizomes) on top of the mound, so the tip is just above the soil's surface. Spread fleshy roots over and down the mound.
Backfill the soil and lightly pack it down. Remember, the tips of the rhizomes will be slightly above the ground. Lightly cover the tips with soil.
Water the area with about 1 inch of water, and lay a 2- to 3-inch layer of mulch only if you are planting your germanicas in the fall.