06/08/2023
The dreaded volcano mulch! The term "volcano mulch" refers to the practice of piling mulch against the trunk of a tree, creating a cone-shaped mound that resembles a volcano. This practice is generally considered harmful to trees, including Japanese lilac trees, and can have several negative effects:
1. Moisture and root issues: When mulch is piled up against the trunk in a volcano shape, it can retain excessive moisture around the base of the tree. This prolonged moisture exposure can lead to the development of fungal diseases and root rot. The roots of a tree need oxygen to thrive, and when mulch is piled too high, it restricts airflow to the root zone, suffocating the roots and potentially causing long-term damage.
Bark decay and pest infestation: Volcano mulch can hold moisture against the bark, which can lead to bark decay and attract insects and pests. Over time, the prolonged contact between mulch and the tree trunk can create a favorable environment for insects and diseases to thrive, potentially weakening the tree's overall health and vitality.
2. Girdling and structural issues: If volcano mulch is allowed to accumulate year after year, it can gradually build up and bury the base of the tree. This can lead to a condition known as "girdling," where the roots and trunk become constricted or compressed, impeding the flow of nutrients and water. Girdling can weaken the tree's structure and result in stunted growth, poor foliage development, and even tree decline or death.
As you can see from the pictures, rot has formed at the base of the lilac tree and is causing significant dieback of the trees crown. Who knows what the roots below the surface of the mulch look like, but I'm sure that its not good.
To ensure the health of your Japanese lilac tree and other trees, it's best to avoid volcano mulching. Instead, apply a layer of mulch around the tree, leaving a small gap around the base of the trunk to allow for proper airflow and to prevent direct contact between the mulch and the bark. This will provide the benefits of mulching while minimizing the risks associated with volcano mulch.