Should Iris Rhizomes Face Forward or Behind the Fan of Leaves?

Preparing the Soil

• Iris will grow reasonably well in almost any soil, as long as it's well drained. Plants don't tolerate "wet feet." Iris will do best, though, in rich sunny soil, so before planting or replanting dig in 1 to 3 inches of compost, well-rotted manure and shredded leaves. Extra organic matter improves soil drainage as well as overall nutrient levels. Cultivate soil several weeks before you plan to plant or divide iris. Incorporate organic or inorganic slow-release 5-10-10 fertilizer -- the numbers indicate the percentages of nitrogen, phosphorus and potassium in the fertilizer..

Planting Iris

• At planting, dig or hoe a shallow hole for each rhizome, leaving a ridge in the center that elevates it almost to surface level. Place the rhizome on top of this ridge with the roots dropping down to spread out on either side. In sandy soil rhizomes can be planted up to 1 inch below ground. Rhizomes need to be spaced at least 8 inches apart, to allow for future growth, though 12 to 18 inches allows leaf fans more room to develop and spread.

In Rows or Drifts

• One approach to orienting rhizomes and their attached leaf fans, or iris "toes" and "heels," is to orient them in rows or drifts with rhizomes facing all the same direction, as University of Michigan Extension suggests. Pointing rhizomes in the same direction helps provide all plants with equal spacing. Planting in drifts in particular lets you group like colors or varieties together. In modified multiple rows, this approach makes it possible to gracefully blend one color or cultivar into others -- quite striking along a driveway or property line can.

In Circles

• Another option, according to University of Minnesota Extension, is to plant in a fairly tight circle, with rhizomes facing in and leaf fans on the circle's perimeter. You'll need considerable space for this approach -- especially if you'll be planting multiple circles -- and you may also need to prepare for digging and replanting rhizomes more frequently than usual, because leaf fans develop on the end and also on the edges of rhizomes. This is not an efficient use of space, but one advantage is that you can cut flowers and otherwise tend plants without walking on or otherwise disturbing rhizomes.

In Triangles

• The University of Nebraska-Lincoln Extension suggests planting iris triangle by triangle, "toes" in and "heels" out, so as individual plants grow they will spread outward away from the toes -- an approach that also makes the most efficient use of space. Creatively aligning these planting triangles can help separate, but blend, different iris colors and cultivars, like drift planting, while also establishing neat rows.