Worm waste

  • Article by: NANCY ROSE
  • Updated: March 30, 2004 - 10:00 PM

Want not with worm waste

By Nancy Rose

Contributing Writer

OI have heard that worm castings make a good fertilizer. What exactly are worm castings and how should I use them?

AWorm castings are, well, worm poop. Earthworms eat organic matter such as leaf litter. The end product of their digestion is worm castings.

In recent years there has been growing interest in using worms to compost household kitchen waste and, on a larger scale, organic farm waste. This has lead to wider availability of worm castings. It's likely that you'll find many sources for worm castings on the Internet. You may also find something called vermicompost.

Since worm products aren't regulated, worm castings are offered under various names. In theory, vermicompost is a less finished product than worm castings and contains both worm castings and compost. That compost may include animal waste, plant waste, and/or shredded paper products.

Pure worm castings should be a finer product that contains only dark, granular worm castings. You might also find worm casting tea products, which are extracts in liquid form.

No matter what the form, worm castings should be considered a soil amender rather than a fertilizer. Specific nutrient levels for nitrogen, phosphorus and potassium aren't listed for worm castings as they are for typical commercial fertilizer, so it's difficult to use it as a fertilizer. Worm castings do contain a wide range of macro and micro nutrients, but the percentages are dependent on what's in the compost that the worms feed on.

There is some evidence that spray applications of worm casting tea can inhibit the growth of some common fungal pathogens on plant foliage. But claims that this spray product also repels insects such as whiteflies have yet to be established by solid scientific study.

So for now, the best use for worm castings is as an amendment to garden soil or to soilless mixes used for potting seedlings or container plants.

Worm castings have a crumbly, well-draining texture, and their nutrients can act as a slow-release fertilizer, though at a generally low level. Worm castings are fairly expensive. I checked the prices on a sampling of Web sites and found prices ranging from 62 cents per pound to more than $1 per pound.

Here's my recommendation: Worm castings, vermicompost and worm castings teas may be worth experimenting with if you're a curious gardener, but don't expect them to provide for all of your fertilizer needs.

OI'm hopeful that the lilacs will be blooming soon, so I want to ask a maintenance question now. Is it necessary to cut the flowers from my lilac bush once the flowers have faded?

AYou can, but it's not necessary. Some gardeners believe that removing spent lilac flowers will improve flowering the following year, but I have found no scientific studies that prove or disprove this theory.

Clipping off spent flowers is mostly a question of aesthetics. If you think the brown flowers or developing seed heads are unattractive, prune them by cutting at the base of the flower cluster.

Remember that next year's flower buds will be set on lilacs by midsummer of this year, so if you do any pruning after midsummer you run the risk of removing next year's flower buds.

Nancy Rose is a horticulturist, writer and photographer. To ask her a gardening question, call 612-673-9073 and leave a message. She will answer questions in this column only.

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