Oddities in Plant Growth
Fasciation in the Indigo Plant
I’m Glad You Asked
Director Lew Feldman
Among the plants in the Herb Garden is the indigo plant, Indigofera pseudotinctoria, a species traditionally used in China and India to treat a variety of ailments, including microbial infections and various inflammatory conditions. As the name implies, the plant is also a source for indigo dye. Recent reports* suggest that indigo-dyed fabrics show both antimicrobial and anti-inflammatory properties, suggesting potential special uses of dyed fabrics as surgical gauze or incorporated into diapers for newborns. Among the other properties of this plant is that it sometimes displays an unusual growth condition known as fasciation, which is a phenomenon in which the tip of a shoot or flower, instead of producing a cylindrical axis that elongates, alternatively, forms a flattened, often “crested-like” tissue.
Fasciation of the inflorescence of the Indigo plant, Indigofera psuedotinctoria.
Many collectors value these rarely occurring oddities, which are believed to arise because of abnormal changes in the levels of plant growth regulators (hormones; probably cytokinins and auxins). A number of explanations have been advanced for these hormonal imbalances, including natural mutations, bacterial and viral infections and insect and mite infestations. It has also been reported that cold (including frost) can cause fasciation, probably by damaging the normally rapidly dividing cells at the shoot tip.
A UC Agriculture and Natural Resources publication (Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide) notes that if the underlying cause is bacterial, that this may affect the health of a plant and lead to premature death. The publication advises that to “control fasciation due to all likely causes (genetic and microbial), one should prune off distorted tissue and not propagate or graft symptomatic plants.”
* Hosain, et al. Assessing Medicinal properties of Indigofera tinctoria extracts, post-fermented dye, and dyed fabric. Authorea. June 03, 2024)