Stand on top of your garden or bare field and look down at the dirt under your feet. If you have at least an acre, you are likely standing on a million of the most powerful tools a gardener could own.

Having worms in your garden is a good sign that you have a healthy soil. Whether you grow flowers, vegetables, fruit, or all of these, they are essential to producing healthy plants.

Earthworms move the garden soil and create fertilizer. Worms live where there is food, moisture, oxygen and a favorable temperature. If they don't have these things, they go somewhere else.

As lumbricus terrestris crawl down they are eating soil, leaves and grass, breaking down organic matter. As they turn the soil, they bring the organic matter from the top and mix it with the soil below. As the worms crawl back up, they bring subsoil closer to the surface and mix it with topsoil.

In fact, worms can eat their weight each day.

With all this crawling up and down and eating, the tunnels worms create help to increase the amount of air and water that gets into the soil. This allows plant roots to spread and bring more nutrients to the plants.

If a plant has many nutrients, it is likely to grow taller and stronger and produce more fruit, vegetables or flowers.

Another interesting job that the worm has is making fertilizer. While the earthworms are crawling and eating, they leave behind valuable castings.

Think about this. If 500,000 worms live in an acre of soil, they could make 50 tons of castings. That's like lining up 100,000 one pound coffee cans filled with castings. These same 500,000 worms burrowing into an acre of soil can create a drainage system equal to 2,000 feet of 6-inch pipe.

Earthworms also secrete slime which contains nitrogen, which is an important nutrient for plants. The sticky slime helps to hold clusters of soil particles together in formations called aggregates.

An earthworm can grow only so long. The size of an adult worm will depend on what kind of worm it is, how old it is and how well fed it is. An earthworm is usually 90 to 300 millimeters long.

A worm's body is made up of small rings, called segments. An adult will have 70 to 120 segments. Each segment has four pairs of small hairs or bristles called setae.

Earthworms have the ability to replace or replicate lost segments. This ability varies greatly depending on the species of worm, the amount of damage to the worm and where it is cut. It may be easy for a worm to replace a lost tail, but may be difficult or impossible to replace a lost head if things are not just right.

Even though worms don't have eyes, they can sense light, especially at their front. They move away from light and will become paralyzed if exposed to light for too long, about one hour). A worm can die if its skin dries out.

Worms are hermaphrodites, meaning they have male and female organs. Worms mate by joining their clitella (swollen area near the head of a mature worm) and exchanging sperm. Then each worm forms an egg capsule in its clitellum.

The capsules are about the size of a rice grain and are laid in the soil.

Earthworms originally came to America with the European settlers in the 1600s and 1700s. As they brought in many of their favorite herbs, vegetables and flowers, the earthworms would tag along in the soil around the roots of these plants.

Those gardeners who practice composting use Eisenia fetida, the red worm, red wiggler, manure worm or fish worm. These worms prefer living in worm bins eating scraps like potato peelings, carrots, lettuce, cabbage, celery, apple peelings, banana peels, orange rinds, and grapefruit. They also like cornmeal, oatmeal, crushed eggshells, coffee grounds with the filter, and tea bags.

Gardeners can encourage worms in their gardens by using dried leaves, grass clippings and aged manure as fertilizers.

Remember, they are free helpers who can do a lot of work, and it doesn't cost much to feed them.