I've been following with interest the thread on using worms to eat the
garbage. Since there seems to be interest in earthworms, I am re-posting a
combination of three posts from one to two years ago. I live in the
Northeast so most of this is about earthworms of this area; the South and
Southwest are different.
As gardeners we have all come to love the earthworm and want our soil to
hold as many as possible. I'm a firm believer that understanding the
earthworm means we can understand how to help keep them. There are over
3,000 species of earthworms, but only a half dozen or so are important to
If you dig in typical northeast garden soil, you are likely to find three
different types of worms. The canonical night crawler, the common field
worm and the green worm.
The new world did not have any of these worms before the Europeans. The
worms were inadvertently brought over in pots and spread throughout the
Northern American soil. We often think that foreign fauna as bad, witness
the Japanese beetle or Gypsy moth; but the earthworm is an import, and
our soils and gardens would be so much more poorer with it.
The night crawler, Lumbricus terrestis, is the largest and likes soils
that are heavy in organic matter like lawns and meadows. When the soil
becomes poorer, the common field worm, Allolobophora caliginosa, and
all its variants become more common. This is a smaller worm with a
pronounced raised band, called the clitellum, about 1/4 of the way down
its body. Both these worms are quite active and feed by bringing down
organic debris in to their borrows from the surface, their holes aerate
the soil and their excretions, called casts, improve the friability of the
soil. The last common worm is called the green worm, Allolobophora
chlorotica, which is a stout greenish colored worm that is quite dormant
and does little to improve the soil.
Figure 1. Common Earthworms
From top to bottom: Night crawler, Field Worm, manure worm, and green
The very active red wriggler, or manure worm, can be found in compost
piles. You know you have a red wiggler when you pick it up: it thrashes
about, wiggling and squirming. The true red wiggler, Eisenia foetida,
has alternating bands of yellow and maroon down the length of its body. A
similar worm, Lumbricus rubellus, is a deep maroon color without the
These manure worms need extremely high organic matter, such as manure or
rich kitchen scraps to survive. Manure worms just cannot live in common
garden or lawn soil. (Unless the soil is very very rich.) So when you
shovel your red wigglers from your compost pile into the garden, you are
dooming these guys to provide nitrogen for your plants by their bodies.
But the life of an earthworm in general is hard. Their bodies are about
70% protein; rich food for many predators. Their major enemies are insect
eating birds, like robins, and mammals like moles. If you watch a robin
hunting, it pauses, cocks it head and then hops. The robins ears can
actually hear the earthworm moving under ground. But the earthworm,
although sightless and ear-less can feel the vibrations of the bird on
the surface. It's the deadly game of survival.
Another major earthworm predator is the mole. This voracious insect
predator loves to dine on white grubs and any earthworm it can find.
Grubs, attached to the root from which they gain their food, can't
escape, but the earthworm can feel the vibrations of the mole digging and
quickly try to flee. The moles own digging conceals the noise of the
earthworm fleeing, so the star nose mole developed a unique method to
find earthworms. It uses its funny looking nose to detect the faint
electrical fields that earthworms (and some other insects) radiate. Not
only does this mole detect and find an earthworm, but it knows how to
bite it so it is paralyzed but does not die. The mole stores the living
worm along the burrow as food for dining at leisure. Once again, nature
Another predator, usually not found in the northeast, is a carnivorous
snail. These snails are long and thin, just right for invading the shell
of another snail and devouring it. But they also love earthworms.
When you till the ground, the earthworms flee the tillers vibration.
(They must think it's a really big mole.) So the active earthworms are not
usually chopped by the tiller. Some earthworms, like night crawlers, have
5 hearts. If chopped in half, they don't die but try to regenerate;
however, sometimes a half gets confused and it end up regenerating a worm
with two heads or two tails.
Tilling the soil does reduce the earthworm population. Not because it
kills or disturbs them, but because tilling aerates the soil, and this
oxygen quickly reduces the organic matter that the earthworm uses as food.
Mulching with green matter will help provide food to earthworms to
replenish what is lost in tilling.
The population of earthworms, in the north, follows a different cycle
then most garden fauna. The population of adults is highest in the
spring, and decreases in the dry summer months, followed by a increase of
young in the wetter, cooler fall. In the hot dry months of July and
August, you often don't find many earthworms. For a high number of
earthworms in the spring, it's important to protect the young and the eggs
Earthworms can freeze solid and still live if the freeze is slow and they
do not thaw out and refreeze often. Any form of ground cover, cover
crops, leaves, mulch or even boards help mediate the freezing and allow
more earthworms to survive the winter. Fields that are plowed and left
bare are almost devoid of earthworms in the spring. Luckily, earthworms
have a high K (reproduction) factor.
Earthworms are hermaphrodites with both male and female organs. They mate
by lying head to tail with each worm producing a temporary skin canal
through which the sperm flows into each other to be stored in a sperm
sack. The girdle like ring around the front of an earthworm, called the
clitellum, later slides along the worm and picks up the mature eggs and
sperm. It falls off the worm and the combination tube, egg, sperm and
mucous form a well protected nest for the worm eggs.
It's quite amazing to watch earthworms “do it”, how they form almost into
one body, incredibly long and slimy, and then break away each darting
back into its own hole. (To chew on some tobacco leaves I suppose.)
One of the major myths, reported by many otherwise informed authors, is
that earthworms come out of their burrows during a rain to avoid
drowning. Worms have no lungs, they take their oxygen directly thorough
the skin, either from air or from water. In fact, rather then fear water,
they love it. It's drying out they fear and dry soil kills them. When it
rains, they come to the surface because it's easier to find a mate in the
flat open ground then in the three dimensional burrows. The wet ground
allows them to move without fear of drying out. To an earthworm, the wet
ground is a wild singles bar.
Earthworms use lots of water since they produce 60% of their body weight
in urine every day. Urea is very high in nitrogen and provides an
excellent fertilizer. The worms in a field easily produce about 50 lbs
nitrogen/acre, which is the same amount of nitrogen that a crop of hay
takes out of an acre! The earthworm casts of contain concentrated
nitrate, phosphorous, exchangeable magnesium, potassium and calcium. All
essential to plant growth. The organic material bound to earthworms and
other soil dwellers is about 1 ton/acre which is released gradually as
they die in the dry summer, providing a great nutrient reservoir for our
As a society, we are so use to going out and purchase what we need to
solve our problems: need to chop vegetables quickly? Buy a food
processor. Need to water the garden easily? Buy a drip system and an
automatic timer. It is so tempting to do the same for insects: need to
eliminate some grasshoppers? Buy some praying mantises. No worms in your
soil, buy some earthworms. Gardening just doesn't work like that. You
must provide conditions for the worms to flourish.
Earthworm populations are limited by the amount of organic matter, water
and survival over the winter. To grow a good earthworm crop, feed the
soil. The ultimate factor limiting worm population is usually food and
water! Night crawlers have been kept alive for 10 years but in the garden
their life span is usually no more then one year, maybe two. It's
necessary to ensure the eggs and young survive the winters.
That's what organic gardening always comes back to: feeding the soil and
the rest takes care of itself. Earthworms need organic debris and mineral
soil for food. The use of artificial fertilizers, be they chemical or
organic, do not provide the necessary food for earthworms. Neither do dry
leaves. Before they fall, the tree sucks out all the essential chemicals
it can and leaves a leaf that has almost no nitrogen in it. At least, not
enough for the earthworm to eat and survive. Grass clipping, corn stalks,
green leaves, and for me the maple whirlly birds, provide good sources.
So when you dig up a worm, realize it is all part of a wonderful cycle,
its life improves the soil, its wastes add great fertilizer, and even in
death, the worms body contributes its nitrogen at a time when nitrogen
may be becoming scare.
While the author's home
page is still available on the web, this page was no longer
available at the time of preparation. As an archival document, we have
limited the scope of our changes to minor spelling and punctuation