Ask a Master Gardener

Photo of an adult earthworm



I see a lot online about how important worms are for our gardens. Why is that? PM

I like how in 1881, Charles Darwin helped put the worms place in our world in pretty clear terms when he wrote “It may be doubted if there are any other animals which have played such an important part in the history of the world as these lowly organized creatures.” As is oftentimes in life, those who are most overlooked and ignored turn out to be essential to our survival, so let’s talk about worms and their importance in our ecosystem.

Worms serve several purposes, not the least of which is their constant digging to make tunnels in the soil. The worms dig with a part of their body called the prostomium. The prostomium is like a large upper lip that serves as kind of a shovel to not only dig but then work that organic matter into their mouths. Organic matter is basically anything that used to be alive… leaves, sticks, insects, etc. After they digest this organic matter, their nutrient rich excrement gets deposited back into the soil. This nutrient rich excrement is known as castings. For those who supported the Tulsa Master Gardeners through our yearly plant sale/fundraiser, you might have noticed we had bags of worm castings for sale the last couple of years. Why? Worm castings are an excellent way to supplement your garden soil, especially the soil in pots since the soil in pots likely does not have any worms.

Science estimates a single worm can produce the equivalent of 1/3 pound of this top-notch fertilizer each year. When you learn that an acre of land can be home to up to one million worms and do a little math, that means over 300,000 lbs. of soil improvement per acre each year. However, this nutritional improvement is not the only benefit associated with worms.

All this digging also loosens up the soil to provide a better environment for growing things. Since healthy soil is about 1/4 air and 1/4 water, it’s easy to see how these tunnels contribute to the process. They also dine on debris on the surface such as leaves, etc. And then deposit those nutrient rich castings into the soil. In addition, they can go deeper down into the soil and bring nutrients back up. It’s really quite a process.

This loosened soil not only helps water and air make its way into the soil, but these tiny tunnels make great pathways for roots to follow as they grow. It’s not hard to imagine where a root would like to grow, into hard packed soil, or down a nutrient rich tunnel.

Interestingly, there are no male or female worms, just worms. However, it does take two to tango, so to speak. Worms can reproduce when they reach adulthood and form a clitellum. The clitellum is a lighter colored portion of the worm that plays host to their fertilized eggs. To make reproduction happen, two worms line up beside one another and secret sperm which then fertilizes the other worm’s eggs. Then the worms go their separate ways to soon work their way out of the clitellum, leaving this cocoon of fertilized eggs to mature on its own.

Here in Oklahoma, we measure our earthworms in inches, but in South Africa, earthworms have been measured up to 22 feet in length. And I’m told that if it was quiet and you were standing over one of these underground behemoths, you could actually hear them moving. This is both very cool and kind of creepy at the same time.

The Tulsa Master Gardeners teach classes in our elementary schools about worms (and other horticultural topics) and this is my favorite class to teach. When people ask me why it’s my favorite, I tell them “Because nobody screams in the class on seeds.” Recently, I was fortunate to teach about worms to some of the boys at the Tulsa Boys Home. There wasn’t any screaming, but there were a few who did not want to hold or touch the worms. Either way, they learned about worms and know they are good for more than just bait when you go fishing.

As my wife has learned how important worms are to our eco-system, our daily walks through the neighbor can take longer than they used to, especially after a rain. Why? Because we now stop to pick up the worms in the street and place them back on terra firma. Maybe this has become a conversation topic for some of our neighbors along the path of our walk, I don’t know. But it might not be so bad to be known as the crazy worm couple.

I mentioned that the Tulsa Master Gardeners teach about worms in elementary schools throughout Tulsa County. We also teach on a variety of other topics including seeds, soil, pollinating insects, spiders, etc. If you are an elementary school teacher or know one, you/they can reach out to us via our website. Right now we are winding down for the school year, but as fall approaches, the online sign up will be posted again so mark your calendar to check back later. See you in the garden!

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at Photo: Keith Weller, USDA Agricultural Research Service,