The word fasciation comes from the Latin word fascia, to fuse, and that is often what this growth abnormality looks like. Affected stems, fruit or flowers appear as though 2 or more have been fused or banded together. At times the unusual new growth looks quite spectacular and unique, and breeders attempt to reproduce the effect. At other times affected plant material appears grotesque and unsightly. The natural occurrence in nature is fairly rare and may be a one-time occurrence or a persistent condition depending on the causal agent.
Types of Fasciation
Symptoms of fasciation can vary depending on the host plant affected and the cause of the fasciation. The growth pattern beyond the point of mutation may be linear, bifurcated, multiradiate or ring fasciated.
Linear fasciation is also referred to as cresting or cristate. This unusual growth is caused when something damages a single cell, typically in the apical meristem (the growing tip), causing it to begin reproducing other mutated cells and more than one growing point. This causes the new growth to begin growing perpendicular to the normal direction of growth, causing a flattening and widening of the growing tip. Stems appear ribbon-like, with ridges formed by the cell walls which gives the fasciated area the appearance of several stems being fused together as one. The fasciated stems gradually become wider and flatter, commonly reaching 5-15cm (2-6″) in width. In some plant species these branches may additionally twist and curl or fan out; the fan-tailed willow is an example. In flowering plants there may be a proliferation of blooms at the ends of these fasciated stems; at other times only, the flower is fasciated and appears flattened and elongated or elaborately contorted. Cockscomb celosia (Celosia argentea cristata) is a good example of the contorted flower growth. Fruit can also be affected.
Bifurcated fasciations occur when a linear fasciation splits in two to produce a ” Y” -shaped double ribbon (Geneve R. 1990).
In multiradiate fasciation the stem is split into three or more short branches (Geneve R. 1990). This condition is commonly known as witches’ broom where a proliferation of shoots form at the growing tip. In flowers 3 or more flower heads fused together and appear at the top of a single stem.
In ring fasciation the growing point folds over and fuses to form a funnel shape (Geneve R. 1990). The occurrence is quite rare. An example is jade Crassula ovate ‘Gallum’.
In the case of bacterial fasciation by Rhodococcus fascians, multiple buds can form on any portion on the plant, that only partially expand, producing a dense cluster of growth called a leafy gall (Pscheidt J.W. and Putnam M. (n.d.)).
Causes of Fasciation
The unusual growth is caused by a cellular mutation in the central meristem (the area where undifferentiated cells are actively dividing and growth occurs), usually the apical meristem (growing tips) but it can also occur in other meristem locations, as in the case of bacterial fasciation. Several factors can cause this mutation:
- Spontaneous mutations
- An inherited trait: such as mummy pea (Pisum sativum), cockscomb (Celosia argentea var. cristata) and Japanese fantail willow (Salix sachalinensis ‘Sekka’) and the mammoth size tomatoes of beef steak, which are all bread for their unique fasciations.
- Environmental conditions: Fasciations in garden asparagus have been attributed to physical damage or pressure exerted on the growing point as it pushes through the soil (Geneve R. 1990). Frost has also been implicated.
- Disease agents: fungi, bacteria and phytoplasmas have been known to cause fasciation.
- Insects and spider mites: can induce fasciations through their feeding damage, egg laying activity or by serving as vectors for the disease agents that cause fasciation. Primrose moths (Schinia florida) are an example, the egg-laying activity of this moth can cause fasciation.
- Hormonal imbalances
- Nutritional deficiency especially zinc.
- Chemicals: such as weed and feed or 2,4-D
- Mechanical injury
Common Host Plants for Fasciation
Fasciation can occur in any kind of plant. It is especially common in cacti and succulents. Other common plants include: aster, carnation, celosia, chrysanthemum, dandelion, daisies, echinacea, foxglove, geranium, gerbera daisies, impatiens, lilacs, lilies, pines, nasturtium, petunia, primrose, roses, smoke tree, snapdragon and willows.
Regardless of the species of plant affected or the cause of the fasciation this unusual growth is sure to catch your attention.
Photo credits: all photos taken by the author unless otherwise indicated.
References
Biology Dictionary (Updated: June 20, 2018). Apical Meristem. https://biologydictionary.net/apical-meristem/
Klingaman G., (2008). Plant of the Week: Fasciated Plants (Crested Plants). University of Arkansas. https://www.uaex.uada.edu/yard-garden/resource-library/plant-week/fasciated-2-22-08.aspx
Klingaman G., retired Extension Horticulturist University of Arkansas, (2008). Plant of the Week: Fasciated Plants (Crested Plants), Retrieved on Feb. 17, 2021 from: Fasciated Plants (Crested Plants) (uaex.edu)
Mahr S. 2011, University of Wisconsin – Madison, Fascinating Fasciation, fasciation.indd (wisc.edu)
Geneve R., assistant professor of horticulture at the University of Kentucky, (1990). Fascinated With Fasciation, American Horticulturist Aug. 1990, pg. 26-31, Retrieved on Feb. 18, 2021 from: 1990-08r.pdf (ahsgardening.org)
Madalyn Shires M. and Kevin Ong K., (2019). Texas A&M AgriLife Extension Service. Fasciation on Roses
National Park Service U.S. Department of the Interior; Saguaro National Park Resource Management Division (2013). Cristate Saguaros. https://www.nps.gov/sagu/learn/nature/upload/Cristate-Saguaros.pdf
Pscheidt J.W. and Putnam M. n.d., (Jay W. Pscheidt, Extension Plant Pathology Specialist, OSU; Melodie Putnam, Director OSU Plant Clinic), Fasciation, Pacific Northwest Handbooks, Retrieved on Feb. 18, 2021 from: Fasciation | Pacific Northwest Pest Management Handbooks (pnwhandbooks.org)
RHS( n.d.), Fasciation, Retrieved on Feb. 18, 2021 from: Fasciation / RHS Gardening
University of California (n.d.), Agriculture and Natural Resources, Fasciation, Retrieved on Feb. 18, 2021 from: Managing Pests in Gardens: Floriculture: Diseases: Fasciation—UC IPM (ucanr.edu)
White V. (June 1, 2015). Scientists reveal the origin of beefsteak tomatoes. New Food. https://www.newfoodmagazine.com/news/17732/scientists-reveal-the-origin-of-beefsteak-tomatoes/
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