While we are all familiar with the mushrooms we find in our grocery stores, I hear concern from home gardeners surrounding mushrooms and other fungi in our backyards.

Are they killing my plants? Where did they come from? Why are they growing in my backyard? What is that white stuff in my soil?

Mushrooms and beneficial fungi are in fact an important part of the living ecosystem that exists outside in our backyards. Mushrooms are decomposers. They decompose dead organic matter that is in the soil, breaking it down to a form that plant roots will consume.

They are nature’s smallest network of hardworking organisms that continually provide the nutrients that our plants need. Both synthetic or organic fertilizers provide nutrients. Mushrooms and beneficial fungi decompose organic matter and produce nature’s free fertilizer. So, are they killing your plants? No, mushrooms do not kill plants.

First, let’s discuss a very common question: What is that white stuff in my soil? Although contacting your local UH Master Gardener program to submit a sample of the "white stuff" is recommended for an accurate diagnosis, the white stuff is most likely a fungi called mycelia. Mycelia is a network of radial fungal hyphae branches that are white in color; in other words it is a network of decomposing arms that entangle dead organic matter.

It is a natural tendency to be alarmed at a white growth at the roots of a dead plant, but the mycelia did not kill the plant. The plant died and then the mycelia moved in to do their job to consume the dead matter.

To determine why a plant died, consult a UH Master Gardener. They are trained to ask investigative questions and direct you to information about your situation.

There are some common scenarios that we hear.

If compost was used to amend the soil and it was not fully "cooked,"or broken down, then nutrients are stolen from the soil to complete the composting process, and the plant can die.

If the compost was not thoroughly incorporated or tilled into the native soil, then too much dead organic matter will be present, and again nutrients are void and the plant can die.

Overuse of synthetic fertilizers cause living, beneficial fungi and other essential microorganisms to die. When the soil is "dead," meaning there are no living microorganisms, the plant will not be able to extract required nutrients to thrive. Amending the soil with compost will repopulate the soil with microorganisms, but it takes time. The plant can die if adequate time is not provided to regain soil health.

So how did mycelia get into your soil? Mycelia is always present. Perfect weather conditions including warm, humid and wet weather can increase beneficial fungi in our soil.

And finally, why are mycelia and other beneficial fungi growing in my backyard? The fact is that they are part of our natural ecosystem and should be regarded as a benefit.

Jayme T. Grzebik is the statewide coordinator for the UH Master Gardener program. Contact your local UH Master Gardener by visiting www.ctahr.hawaii.edu/UHMG.