Common mistakes gardeners make

I am an introvert, which means I would rather have teeth pulled without anesthetic than have to make small talk at a party. So when my first book, “Decoding Gardening Advice: The Science Behind the 100 Most Common Recommendations,” came out last winter I thought I might have a heart attack while having to promote it by speaking publicly at various events. I wrote the book with my friend Jeff Gillman, a horticulture professor at the University of Minnesota and a longtime speaker who is very comfortable in front of an audience. 

We gave our first talk together in February and much to my amazement, it went well. People laughed and asked a lot of questions. No one left early, and I didn’t notice anybody sleeping or doing crossword puzzles or anything. Ever since then I’ve been speaking on my own most of the time and one of my favorite topics is “Common Mistakes Gardeners Make.” I created the presentation myself, which was easy because over the years I figure I’ve made just about every mistake there is to make. Why not spare others a whole lot of back pain and frustration, I say.

There are 22 slides in my PowerPoint talk so I can’t cover them all here. But I’ve picked out some of the highlights for you. I hope they help.

Not shearing back plants

Got tall asters, Russian sage, prairie ironweed, golden rod, phlox, Joe Pye weed, bee balm and a whole list of other plants that flop over like drunken frat boys come mid summer? I did too. But then I read about the importance of shearing back gangly plants and that has made all the difference. Now is a great time to shear tall perennials. For early summer bloomers, shear toward the beginning of the season so you’re not cutting off flower buds if you can help it. Cut plants back to a third or even half using a hand pruner. 

Wait until mid June to shear late-blooming plants like asters and goldenrod. In addition to more manageable height, shearing also encourages fuller branching and promotes reblooming of many perennials. Shearing does delay bloom a little bit, so if you want a plant to bloom more continuously cut back select stems at different time rather than all of them at once. 

Using gravel in the bottom of containers to improve drainage

I’ve done this for years and I’ve advised others to do it too. Sorry about that. While researching our book I found out that despite all the advice out there saying this practice works, soil scientists long ago figured out that water does not travel easily between substances with different pore sizes. While water moves fairly quickly through fine material, it moves much more slowly through something coarse. Extrapolate that out to a pot where you have fine layer of potting soil above a layer of gravel and what you get is soil that must be wet to the point of being soggy before water moves into the gravel layer. So the gravel doesn’t improve drainage, it actually makes it worse. 

Using chewing gum to get rid

of moles

OK, this is not a common mistake. It’s just weird so I like to bring it up now and again. This is an urban legend or whatever you want to call it. Supposedly, if you put gum inside mole holes they will eat it and die because the gum will expand in their stomachs until all hell breaks loose. In reality, of course, gum doesn’t expand in the stomachs of moles or any other creature. What you should do with moles is leave them alone. Yes, they do make tunnels that can be unsightly in lawns and gardens. But this activity doesn’t last long since they spend most of their time out of sight, deep in the ground in their nests and passageways. When they do come out to eat, they mostly feast on mature insects, snail larvae, grubs, and earthworms. They’re not that interested in our plants. 

Adding nitrogen to soil mulched with wood chips

While it’s true that some nitrogen is lost from the top-layer of soil as wood chip mulch breaks down, studies show that it isn’t enough of a loss to cause a problem in most cases. In fact, decomposition of woody mulch is actually good for the soil because it enriches it with nutrients, including nitrogen, over time. So it’s a mistake to add nitrogen just because you’re mulching with wood chips. 

Instead, only add nitrogen or other nutrients if you actually know your soil is deficient. The good news is that soil testing has become much easier in recent years thanks to improved DIY test kits. There are several quality kits on the market. I did a bit of research and decided to go with the Luster Leaf 1601 Rapitest kit, which tests nitrogen, phosphorous, potassium and pH levels. I recently wrote a blog post about the results and how the kit works if you’d like to find out more:

Meleah Maynard is a writer and Master Gardener. Email her a question or subscribe to her blog at