The Length of the Roots for a Louisiana Iris

Identification

• Louisiana irises descend from native species Iris brevicaulis, I. fulva, I. giganticerulea, and I. hexagona, all of which lend a color or shape to the group. A fifth native species, I. nelsonii, is itself a hybrid of other native species. Louisiana irises are beardless iris with open blooms in reds, purples and blues. Newer hybrids bloom in double flowers, some bi-color, in yellows and pinks. All Louisiana irises share a preference for moist, slightly acidic soil and partial- to full-sun exposure. They grow best in wetland areas but also grow in gardens. Louisiana Irises grow from USDA hardiness zones 10 to 5.

Structure

• Like their cousins, the Dutch bearded iris, Louisiana irises grow from rhizomes, thick roots that grow horizontally outward from the plants. Unlike the bearded varieties that sit on the soil's surface, the Louisiana rhizomes grow as much as 1 inch below the soil's surface. As the rhizome grows, as much as 12 inches long, new plants rise along its annual growth nodes. Mulching helps keep rhizomes moist during hot summers, protects them from sun scald and encourages fall growth.

Anchors

• Even the fattest root needs help from additional roots to keep the rhizome from rolling over and to maintain upright top growth, particularly in wet soils where native Louisiana iris species grow. Thick roots grow downward from iris rhizomes to anchor the rhizome in the soil. These roots grow 6 to 10 inches long. Trim these roots when propagating by division to about 4 inches.

Considerations

• The planting location of Louisiana irises will affect their roots. The Society for Louisiana Iris recommends 6 inches for the depth of a raised bed. Rhizomes will try to climb out and roots will circle around the outside of pots set in ponds. When planting Louisiana iris along waterways or ponds, set them into the bank; their rhizomes will grow in the direction that gives them enough water. Iris roots require added moisture in sunny gardens and winter protection in northern zones to perform well. Divide Louisiana iris on the average every 2 to 3 years and plant them 2 feet apart to give rhizomes room to grow and the plants space for good air circulation.