How to Water Potted Iris Plants Grown in Minnesota

Siberian iris rhizomes should be soaked in water overnight before planting them, and then placed 1 inch deep (2 inches if the soil is sandy) and 2 feet apart. When watering potted iris, it's best to do it from the bottom. Potting soil dries out faster than garden soil, but you should still only give your lilies an inch of water per week. Pots made of terracotta may need a little more water.

Daily watering is rarely necessary, except during periods of heat and drought when potted plants may need to be watered daily or twice a day. Newly planted plants may also need daily or every other day watering. Frequent watering can cause shallow roots that are not able to withstand drought or other stressors. To prevent future problems with iris borers, trim and clean your iris plants in the fall.

Fertilize your iris plants in early spring, about 6 to 8 weeks before flowering, and again after the flowers have disappeared. During periods of drought (longer than three or four weeks), water your plants deeply every 3 or 4 weeks, depending on the temperature. If you want to extend the flowering season, plant more than one cultivar of iris. You can find some iris bulbs or rhizomes for sale at your local garden store, depending on the season.

You can also order many types of iris flowers online. The University of Minnesota Extension provides instructions on how to identify iris borers when inspecting your plants in spring and summer.The rhizome-type iris produces larger flowers and includes bearded and beardless varieties, while the bulb-type iris produces smaller flowers and is often used in rock gardens or in the front row of borders for early color.