Marigolds, with their vibrant colors and distinctive scent, have long been a fixture in gardens across the world. Gardeners often plant them believing the flowers’ natural properties deter unwanted visitors. This practice has led to a common belief that marigolds act as a general insect repellent, including against stinging insects like wasps. Determining whether this popular garden flower influences wasp behavior requires examining the specific science of plant chemistry and insect ecology.
The Truth About Marigolds and Wasps
Marigolds are considered neutral or only mildly effective against predatory wasps. Wasps, which belong to the Vespidae family, are not strongly deterred by the marigold’s characteristic aroma, unlike many common garden pests. The belief that marigolds are a universal insect repellent is a misconception that does not align with wasp behavior.
It is important to distinguish between social wasps, like yellow jackets, and the pests that marigolds are known to repel. Some beneficial insects, such as parasitic wasps, are actually attracted to the flowers to feed on nectar or pollen. Overall, marigolds have no significant repelling or attractive effect on major species of stinging wasps in a garden environment.
Chemical Compounds and Insect Interaction
The misconception about marigolds repelling all insects stems from their proven efficacy against certain herbivorous pests. Marigolds contain powerful, naturally insecticidal chemical compounds, such as thiophenes, pyrethrins, and limonene. Thiophenes, which are sulfur-containing organic compounds, are particularly effective against soil-dwelling pests.
These compounds work by disrupting the nervous systems of soft-bodied insects and nematodes that feed on plant tissue. For instance, limonene released by some varieties can camouflage nearby plants, confusing pests like whiteflies and aphids. This targeted efficacy against plant-eaters led to the incorrect assumption that marigolds would also ward off predatory insects like wasps. Since wasps do not primarily feed on the plant, they are largely unaffected by these chemical defenses.
What Actually Attracts Wasps to Gardens
If marigolds are not the primary factor, other elements in the garden attract wasps. Wasps are drawn to gardens because the environment provides for the complex ecological needs of both their adult and larval stages. Their diet switches seasonally between protein sources for developing young and carbohydrates for adult energy.
Wasps seek protein in the spring and early summer by hunting insects, spiders, and scavenging meat scraps. Later in the season, their focus shifts to high-energy sugars, such as flower nectar, fallen fruit, and sweet human beverages. They also require standing water, like bird baths or leaky faucets, for hydration and for mixing wood fibers to build their paper nests. Furthermore, they are attracted to suitable nesting materials, which include weathered wood they chew to create pulp for construction.