homepage logo

Exploring garden myths

By CATHY DUNN - | May 18, 2023

Spanish moss draped from a tree. Despite what some might believe, Spanish moss is not harmful to trees or other plants. UF/IFAS photo

We’ve all heard anecdotes and advice throughout the years about every subject imaginable, and gardeners are among the best at passing along tips and tricks! There are many gardening myths that we may be guilty of repeating without realizing or understanding the science that can debunk many of these assumptions. UF/IFAS has identified a number of these myths that you have no doubt heard, and maybe even repeated, yourself.

I thought it would be fun to explore some of these familiar myths and provide you with the science behind the story so that you can help combat some of these common misunderstandings.

Many new residents who have moved to southern coastal areas from northern climates are convinced that Spanish moss can kill trees. This is false; Spanish moss is an air plant, better known as an epiphyte, and is not parasitic. The tree provides only support to the Spanish moss, and the roots do not penetrate the bark or derive any nutrients from the tree. This myth probably originated when homeowners observed that dying trees often appear to have higher concentrations of Spanish moss than healthy trees. As trees decline, they lose leaves, and this offers an opportunity for Spanish moss to receive additional light which is necessary for growth. While a heavy concentration of moss could possibly shade lower branches, most healthy trees will grow more quickly than the moss, thus eliminating any detrimental effects from increased shade. Tree limbs may occasionally be weighed down by a heavy load of Spanish moss; if the excess weight concerns you the moss can be removed by hand. Since Spanish moss provides shelter to insects and wildlife you should exercise caution when removing it, or better yet have a certified arborist remove the moss.

Every year during the holidays we are reminded that poinsettias are poisonous; this is false. According to “Toxic Plants of North America,” “As a houseplant, the amount of plant material available for consumption is so small that the species is definitely overrated as a hazard.”

Some people are mildly allergic to the poinsettia’s white milky sap, but according to the experts you’d have to ingest a large quantity of poinsettia to receive a harmful dose. The poinsettia’s colorful leaves are tempting for children and pets, so it is advisable to keep the plant out of reach. Cats and dogs that eat poinsettia leaves may develop mild side effects such as diarrhea and drooling, which can be concerning but might not warrant a trip to the vet. The sap actually contains latex, so anyone with sensitivity to latex should be cautious around the poinsettia.

Other holiday plants such as lilies, holly and mistletoe are far more toxic than poinsettias, so please exercise caution with these plants during the holidays.

You’ve probably heard that dish soap is a safe and natural alternative to pesticides. This is False. Dish soap is not a true soap, but rather a detergent that is synthetically produced and designed to be a powerful cleaner. Plant leaves are coated with a “cuticle” or waxy layer of lipids; this layer inhibits moisture loss and protects leaves from bacteria, fungi and pathogens. Detergents are produced to strip oils from man-made surfaces and can actually damage this protective cuticle, resulting in dry, burned leaves. Even soaps designed for hygienic use are formulated with sodium hydroxide, which is a powerful modern form of lye that can cause damage to plant tissues.

Insecticidal soaps are produced exclusively for use on plants and are made with potassium hydroxide which will not damage plant tissue. These insecticidal soaps are usually only 1-2% soap by volume.

Before using any products in the garden always remember that the rule for chemicals and pesticide is: “the label is the law.” If the soap or detergent label does not specify or include use in the garden or as a pesticide, then the product is not designed or approved for that purpose. You can learn more about the pitfalls of using soaps in the garden by searching for the UF/IFAS article “Soaps, Detergents and Pest Manage-ment.”

Next month we’ll explore some additional garden myths. If you have questions about any gardening techniques you may have read about online or heard from a friend, the best solution is to Google that technique preceded by “UF/IFAS.” The University of Florida conducts extensive horticultural research that is readily available online. You can also call your local Extension Office for help with your gardening questions; in Lee County you can reach the Extension Office at 239-533-4327.

Cathy Dunn is a Lee County Master Gardener Volunteer and a member of the Garden Club of Cape Coral. Visit us at gardenclubofcapecoral.com.