Myths abound in the gardening world. The internet provides limitless information, but is it reliable?  Or is it a myth that has floated around for so long it has become accepted as fact? To save your time, effort and money, make sure that the advice you read is research-based from a dependable source. 

In the Garden Buzz, we support research-based information from reliable sources like the Minnesota and other state Extension Services, all of which are supported by the research universities in their state.  Departments of Natural Resources, which also exist in every state, are another reliable source of science-based information.

In this article, we review several gardening practices and reveal which ones are based on science or myth.

MOTHBALLS KEEP RABBITS OUT OF THE GARDEN

False - Through a process called sublimation, mothballs slowly convert from a solid into a gas that repels moths, not rabbits or other undesirable wildlife.  Using mothballs in a way not specified by the label is also illegal and can harm people, pets, and the environment.  

PLACING GRAVEL OR POT SHARDS IN THE BOTTOM OF A PLANT CONTAINER WILL INCREASE DRAINAGE

False - Rocks or shards in the bottom of pots can block or restrict water drainage because they reduce the size of the drainage hole. Water has difficulty moving from fine-grained soil (such as potting mix) to coarser material (such as gravel or pot shards). The water must saturate the fine-grained material before moving on. The best course is to fill the entire pot with high-quality planting mix.  (University of CA Marin Co. Master Gardeners)            

LAWNS ARE LOW MAINTENCE

False - Lawns are maintenance hogs. To keep your lawn looking good, you must water, mow, fertilize, edge, aerate, and weed.  And that's just the beginning. You will also need to trap underground varmints, repair sprinkler heads, (assuming you have a sprinkler system - worse if you don’t - hauling out the hose and repositioning your sprinkler is time consuming and guaranteed to drench you) and seed or patch bare spots. 

That sound you hear? It's your shrubs laughing at all the time you spend babying that water-guzzling grass.  Moral: plant more shrubs or replace your grass with ground cover. (University of CA Marin Co. Master Gardeners)

CRACKING AN EGG UNDER YOUR TOMATO PLANT SUPPLIES NEEDED 

NUTRIENTS

Maybe but not the best practice - Some people bury whole eggs or crushed eggshells in the soil when planting tomatoes to prevent blossom end rot. The theory is that the eggs provide extra calcium to the plants.  While some gardeners swear by this method, scientific evidence does not support its effectiveness.  While the calcium from eggshells will eventually leach into the soil, it may take some time to break down completely. Whole eggs buried in the soil could also attract pests like rodents or raccoons who may dig up your plants to access the eggs.  Instead, focus on overall soil health. Healthy soil, rich in organic matter and beneficial microbes, will provide a much more consistent and reliable source of nutrients for your tomato plants.  (University of Minnesota Extension; University of CA Marin Co. Master Gardeners)

SOAP WILL KILL GARDEN PESTS

True and false - Dish soap can kill small, soft-bodied insects like aphids and white flies but does nothing for insects with hard shells, like Japanese beetles. To be effective, the soapy water needs to not only to touch the insect but also coat the insect's body. This means turning over leaves to reach insects on the underside of leaves. (MN Extension Service; Colorado State University Extension)

Mole crickets and caterpillars hide deep in turf and are difficult to detect. Drenching a small area of turf with soapy water can irritate the pests and cause them to temporarily surface where they can be identified, counted and treated. (Source:  FL Extension Service)

ADDING COFFEE GROUNDS TO YOUR SOIL HELPS ACIDIFY IT 

False - Fresh coffee grounds are acidic, but used coffee grounds are not. They're neutral. Therefore, adding your used coffee grounds won't change your soil pH.  A better idea is to add used grounds to the compost pile.  (University of CA Marin Co. Master Gardeners)

WILTING LEAVES ALWAYS INDICATE THAT A PLANT NEEDS WATER

False – There are other reasons that plant leaves wilt, so it’s worth exploring other causes before soaking your plant in water. In fact, wilting leaves could be due to waterlogged soil (which deprives roots of oxygen).  Overly moist soil can also promote fungal disease.  Certain bacteria may also cause leaf wilt. Another reason leaves wilt is animal damage to the roots.  Gophers and nematodes feed on roots.  Other animals may create tunnels under your plants that reduce root contract with the soil.  Additional reasons for wilting leaves are over fertilizing or excess salt in the soil.  (University of Minnesota Extension, University of CA Marin Co. Master Gardeners)

GRASS CLIPPINGS LEFT ON THE LAWN CAUSE THATCH

False - Thatch is a layer of grass stems and roots, living and dead organic matter that settles on the grass or ground. Excessive thatch, over a half-inch thick, creates an unfavorable growing environment for grass roots.  They cause the lawn to grow very rapidly, inhibiting the decomposition of organic matter at ground level. Lawn clippings are often erroneously blamed for thatch buildup. Lawn clippings are very high in water content and rapidly break down.  Overwatering and over-fertilizing have more to do with the buildup of thatch. (University of CA Marin Co. Master Gardeners)

MEXICAN PETUNIA IS INVASIVE:  DON’T PLANT IT!

Maybe - It is true that native Mexican petunia is invasive and nearly impossible to get rid of once it invades.  However, three non-invasive cultivars have been developed by the University of Florida and are sold as cultivars 'Mayan Purple’, 'Mayan White' and 'Mayan Pink’.  And the sterile cultivar ‘Purple Showers’, taller and larger than its invasive relative, is available at big box stores.  (Source: FL Extension Service)

Note: All these cultivars are treated as annuals in Minnesota.

In conclusion, when you come across advice that is not footnoted, or comes from a dubious source, it is always worth checking with your local extension service or a reliable research source.  That will save you time, effort and money if the advice you have received turns out to be a myth. Click here for the University of Minnesota Extension website.

References

“Coming Clean on Soap in the Garden, https://extension.umn.edu/yard-and-garden-news/coming-clean-soap-garden.

“Living with Nature and Nuisance Animal,” https://www.dnr.state.mn.us/livingwith_wildlife/index.html

“Managing Mexican Petunia (Ruellia Simplex C. Wright) in the Home Landscape,” https://edis.ifas.ufl.edu/publication/EP498

“Managing Plant Pests with Soaps,” https://edis.ifas.ufl.edu/publication/IN1248 

“Mothballs: Regulation, Proper Uses, and Alternatives;” National Pesticide Information Center, http://npic.orst.edu/ingred/ptype/mothball/regulation.html

University of Minnesota Extension; https://extension.umn.edu/manage-soil-nutrients/coffee-grounds-eggshells-epsom-salts

Becky Peterson, “Cracking an egg under a tomato plant.” Ms. Peterson is a Dakota County Master Gardener.

UC Marin Master Gardeners; https://marinmg.ucanr.edu/BASICS/GARDEN_MYTHS_BUSTED/

Photo Credits: www.flickr.com (1),  University of Minnesota Extension (2,4), www.invasive.org (3)