Digging up the Dirt on Earthworms
When talk comes up about the garden, it is usually about the flowers; what can be added, what
can dead headed and what can be divided. All of this is stuff that needs to be done up on the
surface of you garden, but how does the garden work down below? What is it that makes the
soil work for the plants? Well, that would be worms. As unpleasant as they may be, they are
what make the soil “tick” if you will. In fact there are about 2700 different species throughout the
world that all do the same job…basically, making food for plants. It’s a dirty job, but someone
has to do it.
In North America, the most popular worm is the grey-brown night crawler (Lumbris terrestris).
These are the guys you see on the sidewalks when it rains and also the ones the Robins get
every morning. In Australia they have a worm there that can reach up to 3 meters long! I would
hate to be there when it rains. Here we only have to worry about ones that will only reach about
12 centimeters long, which is good, because there can be up to 50 worms per square foot of
soil; each one producing its own weight in castings (excretement) every 24 hours. This is the
reason they play such a large role in soil enrichment. Worms are not picky eaters, they will not
discriminate between dead plant material and dead animal debris, as long as it can be sucked
into their gizzard to be broken down for digestion in the intestines and ultimately discarded.
PLEASE NOTE: compost, however, should only ever contain plant material. The
microorganisms in compost is incredibly complicated which is compromised by adding any kind
of animal debris. Really, all they do is eat and dig tunnels right? Right. Wrong. Right and wrong.
Theses two basic functions do more than meets the eye.
Night crawlers are usually found just under the soil’s surface (about 6-12 centimeters deep). Their
tunneling helps aerate the soil which not only allows oxygen down to the roots, but also increases
water percolation. Both of these things together help in aggregating the soil, which ultimately helps
plants uptake oxygen and water. Tunneling is usually done during the day for these guys because
the moisture in the soil helps to keep their skin lubricated so they can both move and breathe. The
Suns’ ultraviolet rays will quickly kill a worm by drying their skin which suffocates them, which is
why these guys wait until night to come to the surface to feed on any organic debris hence the
term…night crawler. Also this is when their bird predatorsare asleep. Castings are left up on the
surface at night and raw organic material is dragged down into their tunnels to digest during the
day. Worms reproduce by laying eggs. Although each worm possesses both male and female
sexual parts, it takes two of them to fertilize each others’ eggs. They will then lay a capsule that
hardens into a cocoon which will produce two worms. This can happen up to five to six times per
season until it starts getting cold and they then burrow down beneath the frost line to overwinter
and wait to start the process all over again next spring.
So, when it rains, the nutrients from the excrements are washed down into the soil (which is
aerated thanks to these critters). What were once raw, unaccessible nutrients for plants, is now
nutrient-rich tea, available for root up-take. Cultivating every few weeks will assist in folding in the
new organic material with the old and keep the soil aggregate for water percolation. You can help
keep your night crawler numbers up by working in the middle of the day when they are burrowed
deep. This will help avoid digging them up because, contrary to popular belief, they cannot turn into
two if cut in half…they die. Also, keep from over watering or you’ll just be feeding the birds.
Remember: worms = nutrient-rich soil = happy plants. If you’ve got worms, you’ve got happy soil.