How to Mulch Iris

Irises (Iris spp.) prefer dry, quick-draining soil; otherwise, their roots tend to develop soft rotten spots. Mulch is typically used in gardens to help retain soil moisture, but irises only need mulch for winter protection or to suppress weeds in the bed. Irises can grow in U.S. Department of Agriculture plant hardiness zones 3 through 9, depending on the variety, but winter cold can still cause damage to the roots if they aren't protected. Proper use of mulch insulates the roots without causing rot damage.

Shears
Straw mulch
Bark mulch

Instructions

- 1
  Use shears to cut back the iris foliage to within 3 inches of the ground after it dies back naturally in fall. Remove the old foliage from the bed.
- 2
  Spread a 2- to 4-inch layer of straw over the iris bed after the ground begins to freeze. The straw insulates the soil and prevents frost heave from freeze-and-thaw cycles in winter, which would otherwise damage the rhizomes.
- 3
  Remove the top 2 inches of mulch from the bed in spring after the ground begins to thaw and the snow has melted. Remove and dispose of the remaining mulch when new leaves begin to emerge. Pick up the mulch by hand so that you don't break or damage the new foliage.
- 4
  Allow the soil to dry out after mulch removal, which may take several weeks depending on how well the soil drains and weather conditions. Avoid applying summer mulch over wet soil because it can cause rhizome rot.
- 5
  Cover the soil with a thin 2 inch layer of bark or straw mulch to suppress weed growth, applying it only after the weather warms and the soil dries. Pull the mulch back from the base of the irises so that it doesn't rest against the foliage or cover the rhizomes. Moisture trapped in the mulch can cause rot issues if it touches the leaves.

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