Nature on our doorsteps: Fascinating world of fasciation

Rosaleen Dwyer is the County Heritage Officer at South Dublin County Council – every week she gives us an insight into nature on our doorsteps and the beautiful biodiversity of its plants and wildlife.

SOMETIMES, the normal growth patterns in a plant do not proceed according to plan.  When this happens, abnormal growth produces distorted stems, flowers, fruit, or roots.

Usually, the cells in the growing tip of a plant are finely focussed into a rounded point.  As the tip grows, the cells develop into normal stem tissue that grows upright to form the plant’s stem, leaves and flowers.

Sometimes, however, the growing tip can become damaged.

Instead of producing upright stem tissue, the tip becomes flattened and grows out sideways instead.

This causes the growing stem to become wider than it would normally be.  It can look like it has two, three, or four stems that are stuck together, forming a wide ribbon or a band-like stem.

This banded appearance gave rise to the term of ‘fasciation’ for this unusual growth condition.

This term originates in Latin, and it describes being banded or striped.

Two dandelion flowers sit back to back on the one stem in this example of fasciation

The abnormal stems then give rise to a distorted flowerhead.

In Dandelions, instead of the usual single flower, fasciation can result in two, three, four, or even five yellow flowers growing together beside one another at the end of the stem.

The precise cause of the abnormal growth condition is not clear.

The damage to the growing tip might be the result of an infection caused by bacteria, a fungus, or a virus.

It might also be caused by a genetic mutation in the cells of the growing tip, or by an imbalance in the plant’s growth hormones.

Insects might also be a cause, where the insect can damage the cells by introducing a disease to the plant as it feeds.

While the abnormal growth might look very unusual, fasciation usually does not prevent the flowers from developing and producing seeds.

It is not certain, however, if the unusual growth form is genetically passed on to the next generations.