Fasciation occurs as the result of a genetic mutation, which induces the growing tip of the plant to produce a wide, flattened stem, rather than the normal, cylindrically shaped stem. As the stem elongates, it can twist and turn, giving the plant a distorted and often bizarre appearance.  Any plant tissue that originates from the affected growing point can experience fasciation, including leaves and flowers.  Flowers at the end of fasciated stems may appear flattened or tufted, while leaves along the stem may appear abnormally abundant and undersized.

Fasciation is not considered a disease; affected plants cannot cause other plants in the vicinity to fasciate.  In some species, this trait is a permanent part of the plant’s genetic makeup and can be passed from one generation to the next through seeds or via vegetative propagation.  Coxcombs are one example of a plant that is cultivated for its ability to fasciate, resulting in the fuzzy, wavy flower heads that gardeners love.  In other plants, fasciation may be induced by environmental factors such as insect feeding, mechanical injury, environmental stressors or certain disease processes.

Incidental cases of fasciated plants are normally not a cause for concern. These plants are usually healthy despite their unusual appearance. You can remove the plant, prune out the distorted parts or leave it and enjoy one of nature’s oddities.  In the case of fasciation caused by disease, it is recommended to remove the plants to prevent potential spread in the garden.  Home gardeners may have difficulty determining if infection is present in a plant simply from its appearance.  If you want a definitive diagnosis, consider sending a specimen to Texas A&M AgriLife Extension’s Texas Plant Disease Diagnostic for analysis. https://plantclinic.tamu.edu/

Symptoms of fasciation may be mistaken for symptoms of aster yellows, a plant disease caused by a phytoplasma and spread by leafhoppers.  Plants infected with aster yellows present with leaf veins that turn pale, yellowing of new leaves, abnormally bushy growth and deformed flowers.  This disease is fatal to plants and can be spread throughout the garden, so prompt removal of infected plants is crucial.  For information about aster yellows: https://yardandgarden.extension.iastate.edu/article/2024/08/aster-yellows-wreaking-havoc-iowa-what-gives

For further reading on “fascinating fasciation,” see:

https://hort.extension.wisc.edu/articles/fascinating-fasciation

https://byf.unl.edu/fasciation/