Liriope’s Muse: Tree Care Tips from a Master Arborist

What Is Ball Moss?

Ball moss is a member of the bromeliad family, which includes other well-known plants like Spanish moss and pineapples. It typically forms dense clumps about the size of a tennis ball, hence the name "ball moss." The plant attaches itself to the bark of trees using tiny, root-like structures called "holdfasts." Unlike true roots, these holdfasts do not penetrate the tree's bark or extract nutrients; instead, ball moss absorbs moisture and nutrients from the air.

The Negative Effects of Ball Moss

While ball moss does not directly harm trees by feeding on them, its presence can lead to several negative effects:

1. Allelopathic Competition

Ball moss, like every plant has its own unique allelopathic chemicals. The term allelopathy comes from the Greek words allel and pathy, which mean "mutual harm" or "suffering". Think of this like a plants immune system to ward off other plants. These biochemicals influence the germination, growth, survival, and reproduction of other organisms. Moreover, some allelochemicals may function by reducing nutrient availability and essential nutrients.

That said, healthy trees do not typically get ball moss infestations as they are able to naturally ward them off. (1) However, when a tree is stressed (and its natural allelopathy is weakened) it can become inundated with these mossy epiphytes. The moss’ allelopathic chemicals in small quantities is no problem for a tree, however in large quantities they can become highly toxic and negatively influence the trees growth by inhibiting cell division and foliage growth reducing the trees photosynthesis capacity and the overall vigor.(2) This weakens the tree making them more susceptible to pests, diseases, and even other plants/trees due to their reduced allelopathic defense.

2. Reduced Light and Airflow

When ball moss becomes abundant, it can create dense clusters on tree branches. These clusters can block sunlight from reaching the leaves, which are essential for photosynthesis. Additionally, the mass of ball moss can reduce airflow around the branches, potentially creating a more humid environment that favors the growth of fungi and other pathogens.

3. Increased Weight on Branches

Ball moss may not seem heavy individually, but when numerous clumps accumulate, they can add significant weight to the branches. This added weight can stress the branches, making them more susceptible to breaking, especially during storms or high winds. In extreme cases, heavily infested branches may even break off entirely.

4. Competition for Space

While ball moss doesn’t directly compete with trees for nutrients, it does compete for space on the branches. The physical presence of ball moss can crowd out new growth, particularly on smaller branches and twigs. Over time, this can reduce the tree’s ability to produce new leaves and shoots, leading to a decline in overall health.

5. Attracting insects

Ball moss can create an environment that attracts various harmful insects. These insects can range from benign species to those that pose a serious threat to the health of your already stressed trees. For instance, scale and aphids, bark beetles, spider mites, and more. These pests not only damage the tree but they are vectors for disease as well.

6. Aesthetic Concerns

From an aesthetic standpoint, ball moss can detract from the appearance of a tree. While some people find the presence of ball moss visually appealing, others may view it as unsightly, particularly when it becomes dense and covers large portions of a tree. For homeowners and property managers, this can be a concern, especially if the tree is a focal point in the landscape.