There are a number of gardening adages, old wives’ tales, sage advice–whatever you call it, you know exactly what I’m talking about. Every gardener you’ve ever met has an opinion about what works and what doesn’t in the garden. And while there are some recommendations that hold at least a little truth, there are equally as many pieces of advice that don’t do any good at all.
In this article, we’ll scrutinize nine common gardening claims and see if they hold up to science. Keep reading and maybe you’ll learn some new plant pro tips (or you might just find out that you’re following baseless gardening advice).
Fact or Fiction: Gardening Edition
Consider this a game of two truths and a lie, but for the plant nerds.
- Watering seedlings in the middle of the day results in scorched leaves.
Believe it or not, this one’s false.
I used to avoid watering at all costs during the middle of the day, for this very reason–I believed that watering during the heat of the day was more detrimental to seedlings.
The belief is that water droplets can act like a magnifying glass, intensifying the sun’s rays to the point that seedling leaves will burn. But studies have shown no lasting damage from watering seedlings this way.
Another argument I’ve heard is that plants don’t absorb as much water in the middle of the day, and this is a little closer to the truth. Science proves that, yes, water does evaporate more quickly in hot, dry conditions (like those in a greenhouse). This means that water may be evaporating faster than plants are able to absorb the moisture, but this doesn’t mean that the water droplets will burn the leaves.
Yes, bottom watering is typically better than overhead irrigation, but not for the reasons that you think. Bottom watering is just more efficient since it applies moisture directly where plants need it–near their roots. Plus, watering from below means that there’s no backsplash, reducing the risk of foliar disease among seedlings.
In an article published by Michigan State University, author Rebecca Finneran actually recommends watering in the middle of the day because plant leaves dry off more quickly and are less susceptible to fungal disease.
Morning is generally viewed as the best time of day to water, because plants have the rest of the day to dry out, reducing the risk of overwatering. On the other hand, watering in the evening, when temperatures are cooler, could encourage the growth of damping off in seedlings. But if you have to water at night, don’t worry too much–a few evening waterings won’t spell disaster for your garden.
- Playing classical music helps plants grow faster.
For now, we have to say that this one is false.
While there is a bit of debate surrounding music and plant growth, to date there have not been any studies that definitively found that music of any kind directly affects plant growth. There have been studies that found a correlation between music and growth rate, but not without isolating other conditions that factor into plant growth (sunlight, moisture, nutrients, etc).
It has been proven that plants feel vibrations, and perhaps plants that do respond to music aren’t responding to the audible melodies, but the rhythmic vibrations.
Rich Marini, Professor of Agriculture Sciences at Penn State, has come to this conclusion: “The best thing people can do to help their plants grow is provide them with light, water, and mineral nutrition.”
Ultimately, research is still underway and the answer is not yet conclusive. Therefore it’s better to depend on proven growth stimulators like soil, temperature, sunlight, water, and fertilizer to encourage plant growth.
- Dishwashing soap is an inexpensive and effective pesticide.
This one is true, so stock up on dish soap next time you go to the store!
We’ve all heard the advice to add a few drops of dish soap to a spray bottle, mix it with water, and spray on affected plants to keep pests at bay. I’ve tried it myself and had pretty decent success.
According to an article published by the University of Minnesota, soap appears to work for some insects but not on all of them. The article explains that “the working theory is that the soap washes off a protective coating on the insect’s body, causing it to dry out.”
The article author and Extension educator Marissa Schuh goes on to write that “small, soft-bodied insects are the best candidates for management with soapy water. Aphids, whiteflies, thrips, and mites are all good candidates for soapy water sprays.”
By this logic, soap is safe for pollinators like bees and butterflies, so you won’t need to worry too much about accidentally killing beneficial insects. Unfortunately, the soapy spray doesn’t work on larger nuisances like caterpillars and Japanese beetles.
So what’s the magic recipe for aphid-killing soap spray? Schuh recommends a 2% soap solution: that’s two teaspoons of soap to every pint of water. Mix the two together and transfer to a bottle, shake, and spray the bad bugs away!
- Diluting Epsom salt in water creates a solution that aids in seedling germination.
This claim is false and probably started circulating as a marketing technique.
An article published by a Washington State University Master Gardener disputes the claim that an Epsom salt solution improves seedling germination. The article’s author Linda Chalker-Scott explains that “This rather misleading claim has no basis in scientific research. Most seeds are able to germinate in the absence of external nutrients. Most seeds contain enough essential minerals to initiate root and shoot growth on paper toweling moistened only with pure water.”
While Epsom salt has been used to remedy magnesium deficiencies in mature plants, Chalker argues that it just isn’t necessary for seed germination. In fact, adding Epsom salt to the garden or soaking seeds in a salt solution can have a detrimental effect on plants due to an overabundance of sodium.
- Adding coffee grounds to your garden is a good way to lower soil pH for acid-loving plants.
While fresh coffee grounds are quite acidic, used coffee grounds are more neutral in their acidity, so used coffee grounds aren’t all that effective at raising soil pH. Even if you were to add fresh coffee grounds to your garden, it would be months before you would see results. The best way to acidify garden soil is by adding compost and organic matter. Most plants thrive in soil with a slightly acidic to neutral pH, so over-acidifying the soil can be problematic for many garden plants. Always get your garden soil tested at the beginning of each season and add the suggested amendments in the recommended amounts.
- Mulching with fresh wood chips robs nitrogen from the soil.
This one is false too, even though it’s a commonly held belief.
Despite what folks say, mulching with fresh wood chips doesn’t necessarily rob the ground of nitrogen. There is conflicting information about how wood chips affect nitrogen levels, but science says that this isn’t necessarily true.
You can use fresh or aged wood chips to mulch your garden–just make sure that your wood chips are from a reputable source to reduce the likelihood of any dangerous chemicals. The trick is to not mix the wood chips into the soil—you want to keep the wood chips on the surface level only, no deeper.
Wood chips actually contain a lot of nitrogen, and as microorganisms in the soil decompose the wood chips nitrogen is actually added to sub-surface soil. However, microorganisms use some of the available nitrogen in the surface soil in the decomposition process and later redeposit it in deeper layers.
Chalker-Scott published another article through Washington State University that puts the nitrogen-robbing myth to bed. “Many studies have demonstrated that woody mulch materials increase nutrient levels in soils and/or associated plant foliage. My hypothesis is that a zone of nitrogen deficiency exists at the mulch/soil interface, inhibiting weed seed germination while having no influence upon established plant roots below the soil surface.”
So go forth and mulch with confidence! If you’re interested in learning more about how to mulch and what to use, here’s a list of the best mulches for vegetable gardens.
- Placing a cup of beer in the garden will deter slugs.
This one is true! (Can you believe deterring slugs is so easy?)
Skip the salt and use beer instead, suggests an article by Linda Naeve and published by Iowa State University’s Extension program. The article’s author Linda Naeve explains how to set the trap, and also why it’s effective: “A beer trap consists of a shallow container, such as a yogurt cup, buried to within a half inch of the rim and filled with beer. Slugs will find it irresistible, crawl in and drown. You may want to put a loose cover over the beer trap to shade it and prevent rain from diluting it.”
As fun as it is to salt slugs, you might be better off using cheap beer to kill the slugs while you sleep.
- Sprinkling baking soda around your tomatoes will make the fruit sweeter.
False, but there is some logic behind this one.
Baking soda is alkaline, and the thought process here is that making the soil more alkaline will in turn make tomatoes less acidic.
You’d be far better off adding dolomitic lime or wood ash to fix a soil pH issue in your garden, and even making the soil more alkaline won’t necessarily make your tomatoes taste sweeter. Sugars in tomatoes are more related to environmental factors like sunlight and water, and the genetics of the variety itself than soil pH.
For sweeter tomatoes, look for varieties that are known for their especially sweet fruit. Cherry and grape tomatoes will naturally be sweeter than beefsteaks because sugars are more concentrated in smaller fruits.
Make sure that your tomatoes are getting at least eight hours of direct sunlight per day, and even more sunlight can contribute to sweeter tomatoes. You can also taper off watering tomatoes in the weeks leading up to harvest—less water means more concentrated sugars and tastier tomatoes!
- Sunflowers are bad companion plants for potatoes.
This one is true–are you surprised?
Sunflowers, as beautiful as they are, are allelopathic—meaning, sunflower plants release chemicals that can negatively affect the growth of neighboring plants. An article published by University of Arkansas Extension agent Sherry Beaty-Sullivan plainly states that “potatoes and beans grow poorly in the company of sunflowers.”
This doesn’t mean that sunflowers are bad companions for all plants—corn, squash, lettuce, and tomatoes are all reputed to pair well with sunflowers. Just keep beans and potatoes away from sunflowers, since they don’t play well in the garden together.
There are many gardening myths that get perpetuated without scientific backing. It’s important to understand the facts and do your own research before you start implementing any gardening practices. By using evidence-based methods, you’ll be able to yield better results in your garden without any harmful side effects. Keep these tips in mind and happy gardening!
To find books, courses, seeds, gardening supplies, and more, check out The Shop at Greenupside!
Hey – you can sign up for our weekly gardening newsletter here!
Join 1000+ gardeners to get access to news, tips, and information.
Delivered right to your inbox – once per week.
Beaty-Sullivan, Sherry. “Beauty’s Only Dirt Deep.” UAEX, https://www.uaex.uada.edu/counties/little-river/Beautys%20Only%20Dirt%20Deep%200516.pdf. Accessed 6 April 2023.
Chalker-Scott, Linda. “Epsom salts – Wsu.” Wsu, https://s3.wp.wsu.edu/uploads/sites/403/2015/03/epsom-salts.pdf. Accessed 6 April 2023.
Chalker-Scott, Linda. “Wood chip mulch: Landscape boon or bane?” Wsu, https://s3.wp.wsu.edu/uploads/sites/403/2015/03/wood-chips.pdf. Accessed 6 April 2023.
Finneran, Rebecca. “Smart watering in the vegetable garden – MSU Extension.” MSU College of Agriculture and Natural Resources, 15 January 2015, https://www.canr.msu.edu/news/smart_watering_in_the_vegetable_garden. Accessed 6 April 2023.
Naeve, Linda. “Slug it Out with Slugs in Your Garden.” Iowa State University Extension, https://www.extension.iastate.edu/news/2006/jun/070201.htm. Accessed 6 April 2023.
Schuh, Marissa, and Julie Weisenhorn. “Coming clean on soap in the garden.” University of Minnesota Extension, https://extension.umn.edu/yard-and-garden-news/coming-clean-soap-garden. Accessed 6 April 2023.
Stevenson, Alexa. “Probing Question: Does talking to plants help them grow?” Penn State, 24 August 2008, https://www.psu.edu/news/research/story/probing-question-does-talking-plants-help-them-grow/. Accessed 6 April 2023.
About the author:
When not writing content or growing flowers in her native Virginia, you can find Sarah hiking a long-distance trail deep in the woods. Follow along with Sarah’s adventures at http://sarahcolliecreative.com.