If there is one thing gardeners are good at, it is putting waste products to good use. Adding coffee grounds to garden soil is a great example. Smelling much better than barnyard manures, but just as effective, coffee grounds can do wonders for a garden. They can serve as slug repellent, fertilizer, mulch and compost pile ingredient. Like other green-waste products, coffee grounds are quite effective when combined with other materials like manures and grass clippings. If you have not yet considered coffee grounds, give them a try. Here are some tips:
MULCH — Most studies, but not all, have shown coffee grounds to be a bit acidic in nature. This makes them wonderful for mulch for roses, blueberries, rhododendrons, azaleas and other acid-loving plants. A thick layer of coffee ground mulch by itself is not the best thing to do, however, as this mulch can get a bit crusted with mold on the top. Best to mix with shredded wood compost, grass clippings and such. One technique is to put down a half-inch layer of coffee grounds and then top that off with another mulch material.
FERTILIZER — Coffee grounds are an excellent slow-release fertilizer, typically averaging 2.0/0.3/0.6 (nitrogen/phosphorus/potassium). They also add magnesium and copper to the soil. Scratch them into the soil around blueberries, roses and young fruit trees. Since it tends to be acidic, coffee grounds also make a good fertilizer for potatoes.
SLUG/SNAIL REPELLENT — While pulling weeds and prepping planting beds, you may have noticed quite a few slugs and snails lurking about these spring days. Zap them with coffee. Studies have shown that the caffeine in coffee grounds deters and can actually kill slugs and snails. You could even dump a cup of coffee on a fat old slug. Mixing coffee grounds into the soil prior to setting out starts helps control slugs and snails. Basil, bok choy, lettuce, Chinese cabbage — those little starts especially vulnerable to slugs and snails — could be protected with a band of coffee grounds around each start.
Since straw mulches tend to harbor slugs and snails, lay a thin layer of coffee grounds first, then use the straw mulch. Or mix the grounds liberally with the mulch to make a blend.
COMPOST — Coffee grounds make an excellent addition to the compost pile or worm bin. Worms love them. The grounds add nitrogen to the compost pile, helping speed up the composting process. They are clean, weed-free and can help deter unwanted odors.
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Terry Kramer is a trained horticulturist and journalist. She has been writing a garden column for the Times-Standard since 1982. To get in touch with Terry, send an e-mail to style@times-standard.com and put “For Terry Kramer” in the subject line, or write to Terry Kramer, c/o Times-Standard, P.O. Box 3580, Eureka, CA, 95502.
