Marigold Companion Planting for Pest Control
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Keep pests away from your plants with marigold companion planting in gardens and containers for natural pest control.
by Mark Hall
When growing a vegetable garden, have you ever felt dejected and alone? You did your homework and followed all the best advice. You sowed every seed diligently by hand. Under a blazing hot sun, you poured your heart and soul into the care of each tender seedling. Then you found that all sorts of critters were helping themselves to your pride and joy. Everyone seemed to be benefitting from your hard, dedicated work … except you. Such a discovery can be maddening, but don’t despair. You’re not alone. You have a friend, the marigold.
The marigold (Tagates) is considered a companion plant to the rose, the potato, and most famously, the tomato. For many generations, in fact, gardeners have planted marigolds around and between their precious tomato plants for their beneficial qualities. As for me, ever engaged in the battle for garden superiority, the marigold is most certainly a friend!
Marigold Pest Control
The helpful attributes of the marigold are indeed many. First, it can act as a repellant, releasing a strong odor that’s extremely disliked by deer and rabbits. A long list of bugs are also driven away by the same stench, including whiteflies. These tiny pests suck sap from the underside of leaves and spread disease.
The marigold is also able to repel a species of parasitic roundworm which debilitates tomato production. Known as root-knot nematodes, these dirt-dwelling menaces penetrate plant roots and attack the vascular system. Left unable to draw nutrients and water from the soil, the plant will slowly die.
However, research shows that the cultivation of certain marigold crops can help to prevent these assaults. When tilled into the soil in the fall, both French and African marigold plants release chemicals toxic to these destructive microorganisms throughout the next growing season. Only Signet marigolds lack this ability to effectively terminate root-knot nematodes.
Not satisfied with direct assistance only, the marigold also calls for back-up in its defense of tomatoes and other garden plants. Tomato hornworms are thick, heavy caterpillars that grow up to four inches in length. Having a leafy green color, they aren’t detected, at times, until they’ve eaten a surprisingly large number of tomato leaves and some of the fruit.
Fortunately, the heroic marigold has a solution. It attracts an insect, the parasitic wasp, which helps alleviate the problem. Tomato hornworms are a highly preferred host of parasitic wasps, which lay their eggs inside the body of the caterpillar. When the larvae hatch, they begin eating the unwelcome creature. When finished, only a shell of the once big, yet stealthy, caterpillar remains.
Marigold Companion Planting
The marigold also keeps other harmful insects away from certain garden plants by selflessly offering itself as an alternate food source. Enticed by the marigold, hordes of tiny, tomato-eating insects known as thrips turn and begin feeding upon this most selfless of friends. Fortunately, this is a trap, for an army of so-called minute pirate bugs (Orius insidiosus) soon discover the thrips and feast upon them greedily.
Truly, the marigold goes above and beyond to show the measure of its friendship. It not only repels, terminates, and traps organisms harmful to its companion plants, it also attracts a wide variety of pollinators. The marigold provides bees, lady bugs, and other hardworking pollinators with nourishment that is easily accessible and always available. Even though tomatoes self-pollinate, fruit production is increased by these bonus pollinators.
Many generations of highly experienced gardeners have reaped the benefits of planting marigolds in and around their garden. However, there are voices within the field of horticulture which, although they acknowledge some studies on the subject, turn right around and virtually dismiss their viability as a companion plant altogether. Certainly, further research would be worthwhile, for both sides seem to generally agree that our knowledge in this field is incomplete. I know which side of the hedge I’m planted in this garden debate.
How about you? If you’re on the fence, hop down and plant some marigolds in your garden this year. You’ll cultivate a wonderful, new friendship.
Resources
- Dalman, Nate. (2022). Marigolds. Retrieved June 2024.
- Dyer, Mary H. (last updated 2022, December 21). Marigold and Tomato Companion Planting: Do Marigolds And Tomatoes Grow Well Together. Retrieved June 2024.
- Newcastle University. (2019, March 1). How the humble marigold outsmarts a devastating tomato pest. Retrieved June 2024.
- Osteen, Laura. (2022, May 11). How Marigolds Help Your Tomato Plants. Retrieved June 2024.
- Schwarz, Tanner, and Gorny, Adrienne. (2020, August 16). Root-Knot Nematode of Tomato. Retrieved June 2024.
- University of Delaware, College of Agriculture and Natural Resources. The “New” Companion Planting: Adding Diversity to the Garden. Retrieved June 2024.
Mark M. Hall lives with his wife, their three daughters, and numerous pets on a four-acre slice of paradise in rural Ohio. Mark is an experienced small-scale chicken farmer and an avid observer of nature. As a freelance writer, he endeavors to share his life experiences in a manner that is both informative and entertaining.
Originally published in the November/December 2024 issue of Countryside and Small Stock Journal and regularly vetted for accuracy.
