The relationship between plants and insects is an ancient evolutionary partnership, often focused on pollination (entomophily). Plants must attract insects for reproduction, while insects seek plants for sustenance or shelter. This dynamic interplay makes attraction a core survival mechanism for both organisms, as a plant’s success relies on its ability to broadcast compelling signals.
Understanding the Signals
Plants employ a multi-sensory advertising strategy to communicate with insects, often relying on cues invisible to humans. Long-distance communication relies on chemical signaling through volatile organic compounds (VOCs). These airborne molecules, which we perceive as scent, act as a roadmap. Floral aromas like limonene attract bees and butterflies, while other specific chemical mixtures signal the presence of a host plant to herbivores.
Visual cues complement scent for close-range guidance, including the specific colors of petals. Many insects, particularly bees, perceive light in the ultraviolet (UV) spectrum, revealing patterns that act as “nectar guides.” These UV markings direct insects toward the reward, ensuring they land precisely where they can facilitate pollen transfer. The final layer of attraction involves tactile and gustatory cues, where specialized landing pads or the taste of nectar confirm the insect’s choice.
Plants That Draw Beneficial Insects
Many common garden plants draw in insects that provide mutual benefits, such as pollination or natural pest control. Pollinator gardens feature species like milkweed (Asclepias), the sole host plant for Monarch butterfly larvae, and borage, which attracts honeybees. Other flowers, such as cosmos and zinnias, offer open floral structures that make their pollen and nectar easily accessible to a wide variety of bees and butterflies.
Beyond pollinators, certain plants are cultivated to support beneficial predatory and parasitic insects, creating a “bug bank.” Plants from the Apiaceae family, like dill and fennel, produce umbels of tiny, shallow flowers. These provide vital nectar and pollen for adult parasitic wasps, lacewings, and hoverflies. Sweet alyssum is another example, offering continuous blooms that support minute parasitic wasps and hoverflies, which actively hunt aphids and mealybugs on nearby plants.
Plants That Function as Pest Hosts
While some plants attract beneficial insects, others are magnets for unwanted pests due to specific chemical compositions or structural preferences. Gardeners leverage this intense attraction through “trap cropping,” a strategy that exploits the pest’s sensory preference. The core principle is planting a highly desirable “sacrificial” plant next to the main crop, acting as a decoy.
Nasturtiums, for example, are highly attractive to aphids, which congregate on their stems, leaving beans and broccoli untouched. Similarly, Blue Hubbard squash is a preferred host for squash bugs and squash vine borers, drawing these destructive insects away from zucchini or pumpkin plants. This method relies on the pest’s strong attraction to the trap crop’s unique chemical cues. Once pests are concentrated, they can be removed or become a food source for beneficial insects.
The Unique Lure of Carnivorous Plants
Carnivorous plants represent a specialized, non-mutualistic form of insect attraction focused on nutrient acquisition rather than pollination. Species like pitcher plants (Sarracenia) thrive in nitrogen-poor soils and must trap insects to supplement their diet. They attract prey using a combination of visual and chemical decoys.
Pitcher plants display bright, contrasting colors, particularly red, which increases the capture rate of flying insects. They secrete sweet, sticky nectar along the rim of their traps, enticing insects closer. Some pitcher plants emit complex odor cocktails, using compounds like monoterpenes to lure bees and moths, or fatty acid chemicals to attract ants.