The ends of some of my Daphne odora branches look like several branches fused together. What causes this, and is there something I should do?
What you are describing sounds like fasciation, which is a kind of genetic mutation. Professor T. Ombrello of the department of biology at Union County College describes this condition:
Excerpt:
“One interesting type of mistake that is occasionally found in plants is known as a fasciated or crested growth form. It is usually the result of a growing point changing from a round dome of cells into a crescent shape. Subsequent growth produces a flat stem. In some cases fasciation is the result of several embryonic growing points fusing together, with the same flat-stem appearance. [… ] What causes plants to produce fasciated stems? For the most part, we just don’t know. Fasciation has been induced experimentally by applications of plant hormones, severe pruning, wounding, and atypical day lengths. Most, however, appear by chance with no obvious cause.”
University of Arkansas Extension addresses the phenomenon of fasciation.
Possible causes for this condition:
- bacterial infection
- inherited genetic trait
- herbicide, insect, or physical damage to the growing tip
- garden conditions that favor rapid growth
- spontaneous mutations
There are good illustrations and explanations on the blog of Tentative
Plant Scientist, as well.
You don’t need to do anything, unless you would like to remove the odd-looking growth. You may want to look into whether herbicide has been used, or if there have been insects feeding on your Daphne. Also, avoid over-fertilizing, which could promote excessively fast growth.