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Garden Myths Busted: Citrus, Compost and Baking Soda

By Paul Rodman (paulgrowApril 23, 2012

We’ve all heard about them, some call them “old wives tales.” We watched that guy on TV use beer on the lawns, soap on the flowers, and many other concoctions. The question is do these tricks really work? I’m about to tell you.

Gardening picture

Two horticultural professionals took some of the most popular garden myths into the university laboratory to prove or disprove the accuracy of these myths. Dr. Linda Chalker-Scott from Washington State University and Dr. Jeff Gillam from the University of Minnesota tested these myths under controlled conditions to determine if they really work.

ImageImageThe Myth

Will placing citrus peel or citrus tea (orange or lime) on an anthill repel or kill the ants or other insects?
Citrus peels are thought to contain a substance that is fatal to insects (d-Limonene).


The Fact
A mixture made from citrus peel was placed on several ant hills. The result was less than overwhelming. The mixture had little or no effect on the ants. A  spray made from citrus peel was applied to a plant that was infested with mites. It did have some effect on the mites but it also damaged the plant. Use caution when applying any citrus material to plants, the citric acid could damage the plant.


ImageThe Myth

When planting a new tree or shrub replace the soil in the planting hole with organic material such as compost. Everyone knows that plants love "organic stuff" and will grow rapidly.


The Fact
The roots on newly planted trees or shrubs will indeed grow rapidly in the organic material. The problem is when the new roots reach the edge of the planting hole and the native soil. They will actually turn and circle back into the organic material.

The result in that the organic material will actually hinder further root growth long term.  Moisture is another issue, it will actually wick away from the organic material back into the native soil and thus deprive the roots of the moisture newly planted trees and shrubs need. Use the native soil removed when digging the planting hole to backfill after planting. Your trees and shrubs will do much better.


ImageThe Myth

Organic material - especially compost - is always good.


The Fact
It depends where it comes from. Over the past decade many cities and townships across the country have initiated municipal composting programs. The local government collects yard waste from residents and composts it; it is them returned to citizens at no or very little cost.  The problem is that compost can harbor pesticide residue or heavy metals. These contaminates were also found in some manures from chickens and cattle.

If compost contaminated with these products were to be used in a vegetable garden the harvested veggies could contain the chemicals.
If the compost contained trace amounts of herbicides it could affect ornamental plants as well.
If you compost your own yard and garden waste, use only chemical free materials. Do not compost grass clippings that have been chemically treated.
If buying commercial compost look for the STA label, the Seal of Testing Assurance issued by the U.S. Composting Council.


baking sodaThe Myth
Baking Soda makes a good fungicide


The Fact
Baking soda mixed with water has been touted for years as an effective control for several fungal diseases. But does it really work?

Tests were conducted on roses that were infected with powdery mildew and black spot. The mixture contained 1T baking soda, 1 T liquid dish soap and 1 T vegetable oil mixed with 1 gallon of water. The mixture was applied weekly and had little effect on the black spot. It did not perform any better than plain tap water on the powdery mildew.

However a study done in 1992 with a baking soda and oil mixture did show some success if applied when the disease was in an early stage.  In some cases baking soda mixed with oil and water can help.

 A word of caution, baking soda can burn the foliage on some plants test on a small area before spraying the entire plant.

On a personal note, I have found that mixing the oil into HOT water and then letting it cool ensures a better mix.

I hope you enjoyed learning the facts behind some of these popular garden tips and tricks.  As you can see, some are pure myth, while others can work under certain circumstances.  It's always a good idea to check out ANY recommendation before trying it on your prized plants or edibles. Just because a remedy uses ordinary household substances doesn't mean they are safe or effective.  And as is true with most things in life, if a garden myth sounds too good to be true, there's a good chance it is.



  About Paul Rodman  
Paul RodmanPaul Rodman has been gardening for over 45 years. He is an Advanced Master Gardener, and American Rose Society Consulting Rosarian. He is President Emertius of the Western Wayne County Master Gardener Association in Wayne County, Michigan. He currently serves as the greenhouse chairman of this group. Rodman has amassed over 5500 volunteer hours in the Master Gardener program. Rodman is the garden columnist for The News Herald newspaper, in Southgate, Michigan. He has also written for the Organic web site. He is a certified Master Canner and has taught classes on Home Food Preserving for 7 years. He has lectured on various gardening topics throughout southeastern Michigan. His favorite pastime is teaching children about gardening. For the past several years he has conducted classes for second grade students teaching them about subjects ranging from vermi-composting to propagation.

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