Why Are My Artichoke Plants Turning Yellow and Dying?

Artichoke Aphids

• Most plants in the garden are host to aphids at some time or another, especially in those plots that are free of pesticides. Artichoke aphids do not cause problems at low levels, but large populations will cause artichoke plants and flower bracts to curl, turn yellow and begin to wilt. Insects damage plants by puncturing the tissues with their piercing mouthparts and drawing out juices. Aphid populations tend to explode at high temperatures and relative humidity levels.

Aphid Infestation Management

• While several chemical formulations are approved for use in managing artichoke aphids, a less toxic option is neem oil, an insecticide derived from plant sources. While it must be applied more frequently than industrial pesticides, it carries the advantage of being less damaging to beneficial insect populations. Purchase pre-diluted neem oil or dilute by mixing 2 tablespoons of concentrated neem oil in 1 gallon of water, and then thoroughly cover all affected plant surfaces with the spray every seven days until the aphid population is under control. Destroy all infected plant material at the end of the growing season to reduce overwintering populations of aphids and eggs.

Disease

• A more insidious cause of yellowing and decline of artichokes is verticillium wilt, a fungal disease that affects many species of trees, shrubs and perennial plants. It is soilborne and enters the plant through the roots, and then progresses upward through the plant. Older leaves lower on the plant begin to yellow and wilt at first, followed by upper reaches of the stem and leaves. Once an artichoke begins to show outward signs of infection, it is usually too late to save the plant, and it should be removed from the garden and destroyed. Well-fertilized and properly watered plants tend to be less susceptible to verticillium wilt.

Normal Seasonal Decline

• As a perennial, artichokes have a resting period in the winter when the plant naturally begins to decline and withdraw its resources into its roots to prepare for winter and spring regeneration. It is a fairly hardy plant, coming back reliably from year to year in U.S. Department of Agriculture plant hardiness zones 6 through 11. It prefers cool, humid summers and can be stressed by long, hot growing seasons, which may also manifest as yellowing of leaves, especially when water deficient. After several frosts, artichokes typically begin to yellow and shrivel, after which plants should be cut back. At the lower end of the plant’s growing range, artichoke plants should be well mulched for winter protection.