Fungi and bacteria are highly prevalent in gardens and soil. Although a few hundred bacteria show themselves as plant diseases that wreak havoc on manicured lawns and prized plants, millions of beneficial bacteria exist to create a healthy soil food web.
A soil food web is an interconnected matrix of microscopic fungi, bacteria, protozoa and nematodes as well as visible-to-the-eye creatures such as worms, beetles, centipedes and millipedes. They aerate the soil, decompose organic matter, make nutrients available to plants, break down toxins and fix nitrogen. We want these organisms to thrive in our gardens.
A few fungi get a bad rap. For example, University of Hawaii Master Gardeners receive calls and emails about mushrooms, which are the fungal “bloom” of mycelium. They pop up in lawns and gardens in the winter season in Hawaii, spurred on by the wet days and warm humidity.
This fungus breaks down organic matter, making nutrients available for plants nearby. Some home gardeners do not like the sight of mushrooms or fear that small children may consume them. If it is necessary to remove the mushrooms, they can be mowed or removed by hand. But the fact is, they are beneficial to soil health.
Lichens are another fungus we hear complaints about on our gardening helplines. Lichens are actually a symbiotic (mutually beneficial) relationship between a fungus and an alga. The alga produces food for the fungus while the fungus helps the alga stay moist. Lichens can be found on the trunks of trees and on rocks and rock walls all over the world, even Antarctica.
They do not feed from their host and pose no threat to trees or shrubs. Lichens thrive in areas with good air quality and are not usually found in highly industrialized areas. They can be all colors of the rainbow and vary in shapes and sizes. Many photographers seek this fungus as subjects of their work, and entire books have been published with pictures of unique and intricate lichens.
Home gardeners may become concerned at seeing lichen growing on a mature tree, especially one that appears in decline. The fact is, while there may be more lichen growing on an older, less vigorous tree, the lichen is not at fault for the tree’s weakened condition. Leaf drop and a decreased canopy allow more light to reach the trunk, which in turn allows lichens to thrive.
It would be a mistake to remove lichen from a tree or plant with a scrub brush or high-powered hose, which could damage the outer bark that protects the vital internal structures that move water and nutrients.
I hope this winter, home gardeners will celebrate the fungus among us, knowing a bit more about their function in our gardens.
Got a plant question? Find out how to contact your local UH Master Gardener Helpline at www.ctahr.hawaii.edu/UHMG.
Jayme Grzebik is an urban horticulturist with the University of Hawaii College of Tropical Agriculture and Human Resources’ Cooperative Extension Service and statewide coordinator for the UH Master Gardener Program. Email her at grzebik@hawaii.edu.
