This past winter was warmer and drier than expected, and as a result, our local California junipers are very stressed following several debilitating drought cycles. Many desert plants have adapted to dropping leaves to reduce evaporation rates during the summer. Others, like the California Juniper retain their green leaves all year long, dropping older leaves as new ones push out. This is noticeable in cultivated junipers and cypresses as well. Extreme drought reactions may include a more pronounced leaf drop as is happening this year, with the browned leaves evident against the green branches. It is not uncommon to find very old junipers that have just a few live branches coming out of a mostly dead structure, probably survivors of past stressful event cycles. Further compounding the issue, is the rapid spread of mistletoe which can strain the healthiest of plants in drought years.
Bollean mistletoe, Phoradendron bolleanum is a native plant so it is not considered “invasive” in the weedy sense of the word. It has existed probably as long as the juniper. Many species of birds enjoy the mistletoe “berries” which are ingested, digested and then excreted onto juniper branches where the seeds sprout. From there, the root-like structures, penetrate the branch and feed off the juniper’s mineral and water content. The mistletoe has two root structures, one is called “haustoria” where it penetrates the phloem, and the other is called “sinkers” where it penetrates the xylem. Certainly, it would not benefit the mistletoe plant to kill its host, as that would be self-defeating. However, during times of drought or extreme heat, the juniper's vulnerability is exacerbated by the continual drain of resources the mistletoe places upon them.
The mostly mild winter encouraged the spread of mistletoe, due to the lack of freezing cold weather that would normally inhibit the growth cycle.
So what can be done? Decreasing the burden of mistletoe is something we have been trying here in the Puma Canyon Ecological Reserve. Volunteers are hard at work removing the largest clusters of mistletoe. The clumps are easily removed with gloved hands by snapping the leafy pieces off. Mistletoe is toxic, so it’s important to wear gloves and wash hands afterward. While this does not completely rid the plant of mistletoe, it does buy some time for the junipers to maintain their vitality through the summer months. The birds that depend on the mistletoe berries will still be able to feed on them in the springtime, when the mistletoe produces new growth, but the overall amount of mistletoe present will be greatly reduced for now.