By Bev Johnson

Master Gardener 

University of Minnesota’s horticultural  science department’s Julie Weisenhorn says no matter how clever someone’s Instagram handle or slick looking TikTok video is, when it comes to plants, take   planting ideas with a bucket of salt. Some of these “hacks” can actually damage your house plants. This column has been guilty of publishing at least one of them. Blending banana skins in a blender and spreading the result around your rose bush expecting the bush to absorb the minerals in the glop to do anything to the plant is, apparently, magical thinking. It is not doing anything except attracting flies.  Putting it In your houseplants can actually damage them. and it will attract flies.

Yes, the skins are rich in calcium, phosphorus, magnesium, and potassium, but unless they are broken down, plants can’t use them. A better use for banana skins is in the compost.

What about adding coffee grounds, broken eggshells or kitchen scraps to a house plant’s soil? Refer to the above.  To start with, to get any use of these materials, they need to be composted. There isn’t a pot that you could get in the house big enough to compost this stuff. Adding kitchen scraps to your houseplants can actually hurt them by creating a smelly mess and a detrimental growing environment. Yes, coffee grounds do add acid to the soil but the amount of nutrients available varies by brand and type of coffee.  A true story about coffee ground’s ability to acify soil. (Not sure that acify is a real word but you get the idea.)

There was a small flower garden just outside an entry door. Used coffee grounds were thrown in the bed several times a day for years. Every year it was planted with annuals. One year, a red poppy came up a beautiful blue. The coffee thrower knew she had a new color break, so she sent some of the seeds to a seed catalog explaining what they were. The catalog apparently grew the seeds, and the next year sent her a letter explaining that the seeds were from a heroin plant, and they couldn’t sell it for that reason alone and, it bloomed red in their trials. The soil had become so acid it affected the color. This is why we add soil sulfur or other acid to ensure a blue hydrangea will maintain that color and not revert to pink.  

Another myth found on TikTok tells you to rub mayonnaise on your houseplant leaves to make them shiny. To start with, not all houseplant leaves are meant to be shiny. Putting anything on plant leaves interferes with the plants ability to ‘breathe’. All plants have stoma, little holes in the underside of the leaf that allows it to release air vapor when the plants become turgid. Julie says, “it’s a regular process of the plant and physical function”.  If you do have a plant with shiny leaves, give it a bath once in a while to get the dust off the leaves. Too big? Use a damp cloth and wipe the leaves down.

Now about watering plants with ice cubes. Whoever started that idea should have a bath in them. Then they would understand how a plant feels. Sure, it prevents overwatering but leads to a very unhappy plant. Almost all houseplants are tropical or at least, semi tropical. Use only room temperature water on plants to prevent damage. If you are watering an orchid, melt the cubes first. Then you will know how much water to use. Don’t frost the toes of your plants. They hate it and will let you know by not thriving.