Fasciation

Sometimes plants grow in ways you might not expect.

Flattened stem of fasciation in milkweed (Kate Russell)

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Instead of a nice round stem or flower, you get a flattened ribbon shape, or undulating folds, called ‘cockscomb’. This is called fasciation. It is also known as cresting.


Fasciation is a relatively rare physiological disorder that can create some really beautiful mutations. It can occur anywhere on a plant, but stems and flowers are the most commonly seen examples.


How does fasciation occur?

In normal plant development, growing tips (apical meristems) focus all their resources on a single point. This is what gives us straight and/or cylindrical stems and flowers. Fasciation elongates the apical meristem, creating a ribbon-like growth. The Latin word fascia means “a band” and can refer to anything that looks like a ribbon or wide band.

Normal milkweed (left) and fasciated milkweed (right) by Kate Russell

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In some cases, these distortions can create unique bends, twists, and odd angles, or unusual clusters of growth that look like a witches broom. Flowers and leaves growing on these distorted stems may be smaller than normal, more abundant, or have other unique characteristics of their own.


One rare form of fasciation, called ring fasciation, has a ring-shaped growing point that creates hollow tubes.


What causes fasciation?

Fasciation can be caused by plant hormone imbalances, genetic mutations, environmental conditions, or bacterial, fungal, or viral infections. It can also occur for no apparent reason. Environmental factors include chemical overspray or exposure, mite or other insect infestation, and the presence of certain fungi. Exposure to cold and frost can also cause fasciation. Unless the fasciation is caused by bacteria, it is not contagious to nearby plants. 


Plants affected by fasciation

In addition to my milkweed, this condition is most commonly seen on nasturtiums, geraniums, dandelions, and ferns. It has also been seen on fruits and vegetables, such as asparagus and broccoli.

Fasciated (top) and normal (bottom) asparagus spears from UW-M Extension

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Some plants are prized and propagated simply because of their fasciation. I look at it as a nice little surprise from the garden.


Have you seen fasciation in your garden?