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Gardening: Garden with the facts

Social media have made it easy to share information with the world. Gardening is a common theme. However, as you know, you can’t believe everything you read online. Ideas or observations that haven’t been confirmed or tested through research make their rounds on the Internet, causing frustration and even danger.

As a Master Gardener, I am asked to teach people about gardening using science-based, usually peer-reviewed, information that comes from research. This allows me to be confident in the information I provide has been researched by numerous people and has been found to be consistent in a number of settings and conditions.

Land-grant universities are good sources of information. Most questions can be answered at the University of Minnesota website: http://www.extension.umn.edu/garden Make sure you get science-based gardening information, you can also find other university extension resources online.

Following are examples of garden misinformation I have found online. The examples come from a variety of sources.

Homemade pesticide alternatives: While using pesticides is a matter of personal choice, many people are turning to homemade alternatives for some pest control. While I do think that some of these work, there are some definite duds circulating. One I have seen is using baking soda instead of fungicide. While changing pH will limit fungal growth, dry baking soda will not have an effect and will quickly wash off. I have also seen insecticides using tobacco. This is a BIG no-no! Tobacco carries tobacco mosaic virus, which infects a wide variety of plants including tomatoes, potatoes, etc. The virus can even survive on a smoker’s hand or cigarette butt even after burning.

Pollinators only like native plants: The premise is that native bees and butterflies can only survive on native plants. While natives are good, there are many plant qualities that make them attractive and nutritious to pollinators. A diverse garden is best for attracting pollinators.

Compost tea suppresses disease: The practice of making compost tea involves a slurry of water and compost. The idea is to spray this on plants to reduce diseases, since the good bacteria from the tea will keep bad bacteria at bay. Research shows that there is no disease suppression (most likely because the bacteria will quickly die off when dried).

Vinegar weed killer: This is one that I see quite frequently. Well-meaning gardeners want an easy way to control weeds without the use of traditional herbicides. The version I see most uses vinegar in combination with dish soap, which acts as a surfactant to make the vinegar spread over the plant. The gardener is supposed to apply the vinegar to the plant, preferably on a hot, sunny day and wait for miraculous results. The problem is that the vinegar is going to do a disappointing job as a weed killer as only parts of the plant where the vinegar touches will likely be damaged and turn brown. On small plants, this may be the entire above-ground part of the plant. On large plants, it is unlikely that the whole plant will be damaged. It is nonselective, so any plant that it touches can be burned. And the big problem is that this does nothing to kill the roots. The problem is even greater if you are dealing with perennials that come back from the roots — the vinegar does nothing to damage them, and the plant will be back within a few weeks.

Household vinegar that you buy at the grocery store is 5 percent acetic acid and 95 percent water. Some of the internet sources say that you should find more acidic versions, such as a 20 percent solution that is sometimes called horticultural vinegar. This product is much more dangerous than even traditional herbicides such as RoundUp. Contact with skin will result in burns, your nose will burn and water, blindness can result from eye contact, and it will kill small wildlife such as frogs and insects on contact, which is something even RoundUp won’t do. Note: Traditional herbicides can be used safely when applied sparingly and according to label instructions.

Marigolds repel pests: This myth has been around before the age of the Internet, but it has spread even farther thanks to posts, tweets and pins. This practice says that planting marigolds around your garden will ward off insect pests. It is true that relatives of marigolds do produce chemicals that repel or even kill insects. Pyrethrin chrysanthemums produce a compound that is extracted and sold as an organic insecticide. If insects are a problem and you want to control them organically, use one of the products that contain the pyrethrin extract as a general insecticide.

It seems people get their gardening advice from shared content on the Internet and become unwitting victims of Internet myths. While gardeners and those who share the false information may do so with the best of intentions, they still help to perpetuate myths that make gardening harder and maybe dangerous.

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