Column: Debunking a few common gardening myths, such as where to put that banana peel

Jane Bloodworth Rowe [Courtesy]

VIRGINIA BEACH — A recent conversation with Alexandra Cantwell, adult education manager at the Norfolk Botanical Garden, showed me much of what I thought I knew about gardening was myth.

“You might hear anecdotal evidence that some of these things work,” she told me. “People say, ‘My grandmother did this and had a wonderful garden.’ But I’m just giving information that’s based on research that I’ve read.”

Some of Cantwell’s myth busters follow for your consideration.

Put away the Epsom salt. Some gardeners rely on Epsom salt, which adds magnesium to the soil, to prevent blossom end rot in tomatoes, but Cantwell said this condition is caused by a lack of calcium, not magnesium. Adding magnesium can be counterproductive because it can inhibit the plant’s absorption of calcium. I have also used it when I was setting out leafy, green vegetables such as spinach or kale. While I thought it helped produce some very vigorous kale and mustard greens, that’s probably more the result of an active imagination than of the Epsom salt.

“Most soils aren’t deficient in magnesium,” Cantwell said, “and you really should have your soil tested before you add anything. Most people don’t realize how much chemistry is in play with the soil.”

Put eggshells in the compost bin, not directly in the soil. Some gardeners add crushed eggshells directly to the soil when they’re planting under the naïve belief that they’re boosting the soil’s calcium level. But eggshells don’t really contain much calcium – and they take a long time to break down so any benefit probably won’t come in time to help this season’s plants, Cantwell said. 

Instead, put your eggshells into your compost pile and let them break down and add their trace amounts of calcium to the other materials. Another use for eggshells is to place the sterilized, well-crushed shells out for birds to eat, particularly in the spring when they’re nesting. A female bird requires a lot of calcium to produce healthy eggs, and the crushed eggshells will give her that boost. Cantwell does caution that they need to be sterilized by microwaving them for a few seconds.

Don’t bury banana peelings or whole bananas directly into the ground. Before talking to Cantwell, I admit that the spring and fall ritual of burying one-half banana next to my gardenias and clematis plants was an almost religious one. I would have sworn that it helped to produce both leaves and blooms. Again, that’s probably more imagination than any direct correlation, according to Cantwell.  

Bananas actually don’t contain that much potassium, and burying them into the ground near the plant’s roots can encourage rot. Like eggshells, bananas belong in the compost bin, where they will break down and add some nutrients to the other materials.

► Coffee grounds really don’t change the pH level of your soil or discourage pests. But they can inhibit water flow if added directly on top of the soil. Still, they’re a good source of nitrogen. Coffee grounds have become popular with organic gardeners, and some frequent coffee shops to collect large amounts of used grounds.  

That’s fine, as long as you compost them or bury them into the soil rather than placing them on top, Cantwell said.  

A layer of coffee grounds on top will make the ground hard and compacted. This makes it difficult for water to penetrate, seeds to germinate and very small plants to thrive.Some think coffee grounds increase the soil’s acidity, but the Ph level is actually at levels considered neutral, Cantwell said.  Besides, most soils in this area are naturally acidic. They also really don’t have enough caffeine to repel insects. The benefit of grounds is that they add nitrogen, but add them to the compost bin or mix them well into soil.

Cantwell also encourages gardeners to mix at least an equal part of carbon-rich materials, including paper or leaves, into the compost pile with the green materials or food scraps. Avoid meats, fish or oily foods, and turn the pile occasionally. If you do this, you shouldn’t have odors. With today’s tumblers or bin composters, you really don’t have a good reason not to compost.

So, put away the Epsom salt and toss your eggshells, coffee grounds and banana peels into the compost pile.

The author is a regular contributor to The Independent News. Her journalism also has appeared in The Virginian-Pilot. Visit for more information on sustainable gardening.

© 2020 Pungo Publishing Co., LLC

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