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MMWD Blog: Think Blue Marin

Welcome to our blog! Written by staff at MMWD, “Think Blue Marin” explores all things water in south and central Marin—water supplies, conservation, new projects, watershed management, and more.

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Jul 15

A Living Sponge

Posted on July 15, 2016 at 11:53 AM by Ann Vallee

by Charlene Burgi

For most of us, sponges are something we typically think of as an aid to washing cars or dishes. Some people might envision the sponges that live in the depths of the ocean. But how many consider their soil a sponge—or even a living sponge?

sea sponge
Sea sponge. Photo courtesy of
Dr. Rick Tegeler (a friend since
junior high school days)

You might say that is a stretch, or argue that sea sponges are animal while soil is mineral. But don't forget the build-up of humus typically composed of mulch, decomposed plant and animal matter, and other organic material that we add to our gardens. Through our actions, we can create sponges in our gardens as beautiful and alive as oceanic sponges.

This lesson came to light for me last week as I left Lassen County behind and headed for the great Northwest. Everywhere I went I found pristine lakes and rivers as well as dense vegetation. Wild tiger lilies sprouted up and bloomed along the glaciated trails where I meandered.

The forest floor
Another living sponge:
the forest floor

I noticed the forest floors where I walked gave way with the weight of my steps. It was as if I were stepping on thick, damp sponges. The soil was teeming with life directly underfoot! Plants flourished in this rich environment.

As I walked, I thought of how my own garden had the same quality of sponginess. Last year, my beloved late husband Jack used bags of hydromulch (left over from a landscape job) in the garden walkways. That project last year made for an amazing regeneration of plant material this year. Petunias are now growing wild where that thick layer of hydromulch was spread. Tomato and squash seeds are popping up as if to create a forest of their own. The garden is as alive as the soil that supports it.

Wild petunias
 Volunteer petunias
In addition to supporting healthy plant life, the benefits of creating that living sponge in your garden include water retention. Water is absorbed, held, and released slowly to the root systems of your plants. Organic material in that sponge-like soil also releases nutrients that support the beneficial fungal mycorrhizae that the root systems of plants depend upon.

Creating a living sponge in your garden can be as simple as adding compost material and organic mulches in thick layers. (You may even qualify for an organic mulch rebate from MMWD.) Over time, as with the forest floor that I trod upon, the soil will take on a sponge-like spring as you walk upon it, and plants will flourish as you have never seen before.


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