- Baking soda can be useful as a fungicide when mixed with water and sprayed on the affected plant very early in the infestation of powdery mildew.
- Banana peels are high in potassium, but they can also extract significant amounts of nitrogen from the soil, which results in less nitrogen for greening up plants.
- Coffee grounds are great in compost bins, but they can become a barrier to moisture, nutrients and air movement when applied in thick layers.
Just when I thought opening social media wouldn’t raise my blood pressure, I discovered another “must do” garden hack that is really a “don’t you dare”! And then I started hyperventilating again.
Hopefully, you’ve been talked out of watering your orchids with ice cubes; been convinced that sugary soda drinks will hurt ailing plants, not heal them, and you understand that vinegar is for salads, not killing weeds.
Even when a pantry item does have benefits in the garden, there are usually downsides. Take for instance baking soda.
Is baking soda good for plant fungus?
Baking soda is often touted as a control for powdery mildew, and in fact, it can help. Powdery mildew is a fungal disease that affects many types of plants from squash to roses. The distinctive white powdery spots on the leaves and stem quickly spread to cover the entire plant.
The theory is baking soda is supposed to disrupt fungal spores that land on the leaf surface. It’s not a new idea. It was first published in a report by Jesse Currey, a rose enthusiast, in 1924. Since then, various combinations of baking soda and water have been tried and tested. The findings seem consistent.
Baking soda can be useful as a fungicide when mixed with water and sprayed on the affected plant very early in the infestation of powdery mildew. The aforementioned downside is that baking soda is sodium bicarbonate — a salt. Since rain and irrigation will wash away the baking soda, repeated applications will be needed. This is going to eventually cause burned foliage and possibly a buildup of salt in the soil, which is not something you want.
If you want to try this, the University of Florida recommends one tablespoon of baking soda per gallon of water plus a spreader-sticker, like a few drops of dish soap. Measure accurately. Too high a concentration turns “help into herbicide.” Our summer heat and frequent rains may render this method disappointing.
Try, instead, driving past the grocery store and heading straight to the garden center for a commercial spray product labeled specifically for this disease and your plant. As always, follow all label instructions.
Check the science first:Those viral TikTok gardening hacks could actually kill your plant
Can I put banana peels directly in my plants?
My next “what are they thinking?” myth is really several in one. You’ve seen them. One variation or another of chopping up fruit and/or vegetables and using them as fertilizer. For our purposes, let’s focus on banana peels.
Yes. Bananas and their peel are high in potassium.
Yes. Potassium is one of the three essential macronutrients in fertilizer and is essential to strong plant growth.
Potassium (identified as K on the periodic table of elements) keeps roots healthy and supports flower and fruit development. Strong roots enable plants to tolerate stress such as drought, and to fight off diseases.
So, why not bury the peels and allow all that good potassium go right to work on your, say, roses?
Meet Dr. Jeff Gillman, director of the UNC Charlotte Botanical Gardens, horticultural scientist, author and myth buster, who offers, “As soil microorganisms work to break down the peels, they extract significant amounts of nitrogen from the soil, which results in less nitrogen for greening up plants.”
Add to that concern, just how much potassium should your plant receive? How much is already present in the soil? Just how much is one banana peel going to provide? And, particularly in my garden, which animal, free range or domestic, is going to dig it out?
A better way to make use of banana peels is to take your morning peel straight to the compost bin. Forego the chopping, digging, guessing and chasing the dog out of the roses. Compost will not only add nutrients back to the garden, but it will also provide beneficial microbes and improve the texture and composition of our sandy soil.
And while you’re on your way to the compost bin, why not scoop up the grounds from your morning cup of coffee to go to the bin with you.
Which is the perfect segue to discuss the last myth du jour: coffee grounds.
Are coffee grounds good for plants?
While many of our bins contain them, some gardeners still recommend sprinkling coffee grounds directly onto the soil next to their plants. They claim coffee grounds do everything from repelling cats, killing slugs, preventing weeds, to acidifying the soil, adding nitrogen, and more. But the information “they” offer is more anecdotal than science-based.
Generalizations can get a gardener into trouble.
Coffee grounds are great in compost bins. They are considered a “green” or a nitrogen-based additive. They are around 1-2% nitrogen which becomes available to plants once the grounds are broken down.
However, different plants react differently to coffee grounds in or on their soil. Researchers have found that some plants benefit quite a bit, while other plants, like tomatoes, seem to suffer. Other plants appear to tolerate them unless they are fresh. Used as a mulch or compost, coffee grounds can enhance germination of some seeds but will slow germination of others. That’s why researchers suggest limiting the amount of coffee grounds to no more than 20%-25% of the compost bin’s total volume.
As for using coffee grounds by themselves as mulch, coffee grounds are finely textured and easily compacted. They can become a barrier to moisture, nutrients and air movement when applied in thick layers.
There’s a common belief that because coffee is acidic enough to give us heartburn, the acidity remains after brewing, making this a good mulch for our acid-loving plants. Not true. The pH of the grounds is actually around 6.5 pH, close to neutral and only slightly acidic. pH levels will fluctuate over time.
All this makes coffee grounds and banana peels better additions to your compost bin/pile than directly on your plants.
Hopefully these little mythbusters will help you make better decisions about caring for your plants. But to always be sure that the video on social media is the real deal, check them out for yourself by going to "Ask IFAS” website at https://edis.ifas.ufl.edu/. That will take you directly to the University of Florida’s site and all the current, regional, science-based information you’ll need to be a better Florida gardener.
Paula Weatherby is a Master Gardener Volunteer with the Duval County Extension Service and the University of Florida/IFAS. For gardening questions, call the Duval County Extension Office at (904) 255-7450 from 9 a.m. to noon and 12:30 to 3:30 p.m. Monday-Friday and ask for a Master Gardener Volunteer.
The Key Points at the top of this article were created with the assistance of Artificial Intelligence (AI) and reviewed by a journalist before publication. No other parts of the article were generated using AI. Learn more.
