by Emma Murphy, Master Gardener

Gardeners have been passing down tips, tricks, and knowledge for generations. Some of this advice is science-based and works, but much of it is a mix of folklore and superstition. While some of it is benign, some of it may actually harm your gardens or have you spending money when you don’t need to.

Here are five of my favourite garden myths – there are hundreds out there – just google ‘garden myths’ and you’ll see what I mean.

I think social media has intensified the problem – in the past information spread through word of mouth, often handed down through generations. Now anyone with a computer can claim to be an expert, and provide inaccurate information that others will share.

Part of my reason for becoming a Master Gardener was to expand my gardening knowledge and share my passion for growing with others using solid, science-based information. We offer our services to the public in many forms – through presentations, advice clinics, answering email queries, and publishing blogs like this one!

The Master Gardeners of Ontario (MGOI) website shows where all the Master Gardener groups are located – find yours and their website and take advantage of their knowledge and expertise. If they don’t have the answer they will go research it for you.

MGOI also has a great Facebook page where you can post questions to Master Gardeners. And I highly recommend The Garden Professors Facebook page for science-based gardening information.

Make sure to follow the Peterborough and Area Master Gardeners through our
Weekly Blog (by clicking on ‘Follow’ in the left column on the homepage)
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Twitter or reach us at contact@peterboroughmastergardeners.com

Myth: You Should Stake A Newly Planted Tree

Truth: Unless it’s top-heavy or in an especially windy site, your tree does not require staking. Some movement is actually good for young trees. I loved this description “Just as our muscles grow larger with exercise, tree trunks grow thicker and stronger when they’re allowed to move.”

The response of trees and plants to wind is called thigmomorphogenesis (yes that’s a word!). The buffeting from winds releases ethylene gas, a growth mediator that triggers the formation of wood-strengthening lignin.

While staked trees tend to grow taller, their trunks are skinny and weak, so if you decide you must stake, stake as loosely as possible and only for a short time (no longer than six months). Make sure to use something soft against the tree bark to keep from cutting into it. But best to practice tough love – your tree will appreciate it.

Myth: Gravel in The Bottom of Containers Improves Drainage

Truth: This myth will not die. We’ve all been told to place stones or pieces of pot at the bottom of our containers “for drainage”. The reality is that added gravel or rocks to the bottom of your pot will actually accelerate the potential for root rot, rather than preventing it. Water is pulled down through the container by gravity and builds up near the drainage hole. A layer of gravel at the pot’s base serves as the drainage hole and collects water in the same way. So gravel actually moves the pool of water higher up the pot, where it damages your plant.

As long as there is a hole in the bottom of the container, water will find its way out without the need for stones.

Myth: Add Epsom Salts To The Soil Helps Tomatoes Grow

Truth: You would think it was a miracle cure for everything
“It helps seeds germinate”
“It makes plants grow bushier”
“It can prevent blossom end rot in tomatoes” (see bonus information at the bottom of this blog!)
“It can prevent transplant shock”
“It results in more flowers”
“It increases chlorophyll production”
“It deters pests, such as slugs and voles”
“It reduces the total amounts of fertilizers needed”

Magnesium sulfate, or Epsom salt, is a naturally occurring mineral consisting of magnesium and sulfur (MgSO4). Magnesium is a necessary element for plant growth but adding unnecessary salts to your soil will destroy your soil structure over time. You are better to simply add compost or worm castings to the soil. There are decades of research that has documented damage done to both plants and soil with overuse and misuse of magnesium sulfate. Want to read more about it? Check out this peer reviewed study by Washington State University’s Extension Center (click here for more of their excellent science-based studies). The best thing epsom salts can be used for is a nice hot bath after working hard in your garden all day.

Myth: You Can’t Grow Anything Near A Black Walnut Tree

Truth: This one is a personal favourite, since I have extensive flower and vegetable gardens in the vicinity of two almost 150-year-old black walnuts. While the roots of black walnut (Juglans nigra) do release an allelopathic chemical known as juglone that inhibits the growth of some plants, the idea that nothing grows under a walnut started gaining traction in the 1920s when a Virginia researcher saw his tomatoes were suffering and just assumed the nearby trees were at fault based on folklore he had heard. Washington State University put out an excellent peer reviewed paper in 2019 explaining the history of walnut allelopathy.

Enjoy your walnut trees! Not only are they robust landscape plants but they provide food and habitat for wildlife and birds. Here’s my lovely perennial garden under my walnut tree (and featured in Linda Chalker-Scott’s paper mentioned above) and my previous blog specifically on this topic.

(Bonus – information on Blossom End Rot)

Research has shown that calcium deficiency is not the cause of blossom end rot. Egg shells won’t correct it. Epsom salts (which are magnesium sulfate) won’t correct it. Nor will coffee grounds, Tums, calcium sprays, dairy products, or any of the other things that are usually recommended for it. It just corrects itself. It’s not caused by a fungus, bacteria, or virus. It’s not in the soil. It’s an internal condition of the plant. The cause appears to be simply environmental: low temperatures at night, fluctuating temperatures, watering too often, etc. Ammonia fertilizer is linked to it, so some forms of plant food can be a problem. But basically: just pick off the fruit that are affected, water more deeply and don’t allow the plant to get severely drought stressed (daily watering is probably not necessary unless you have unusually fast-draining soil or are growing in a container). The next fruit will probably be fine. It’s usually a problem with the first tomatoes, peppers. and squash that set in the season and the rest come along fine.