The Leaves Are Turning Yellow & Curling on My Knockout Roses

KnockOut roses get pests and environmental problems.

KnockOut roses are low maintenance plants that bloom repeatedly and have fewer problems than standard rose bushes, but they are not immune to pests and environmental stressors that can yellow and curl plant leaves. Leaf change is not a serious problem, however.

Causes

Pests like mites or aphids nibble plant leaves and can cause leaf yellowing or browning and leaf curl. Soil that is nutrient deficient in nitrogen, iron or calcium can also cause leaf change in your KnockOut roses. Environmental stressors like high heat, excess water, excess fertilizer or too much shade can also cause leaf change.

Prevention

If you give your KnockOut roses the right care from the start, you can reduce leaf yellowing and curling. The roses need full sun and regular fertilizer. Use a slow-release fertilizer in early spring. Have your soil tested for nutrient deficiency before you plant.

Solution

Examine the plant for pests. If you see insects, use insecticidal soap to kill them. Watch the level of sun your plant gets and prune back your KnockOut rose so all leaves have access to sun. While you can't control the heat, you can give your rose enough water during hot weather, but not enough to flood the soil and create boggy conditions.

References

• Gardening Know How: Reasons for Rose Leaves Turning Yellow; Stan V. Griep
• Rose Care: Nutrient Deficiencies
• University of Minnesota: Rose Diseases; F.L. Pfleger and S.L. Gould; 1998
• LSU Ag Center: KnockOut Roses Require Care; Dan Gill, Kyle Huffstickler and Allen Owings; August 2010