Japanese Beetles, those shiny, copper-winged pests, can wreak havoc on your garden, devouring leaves and leaving your prized plants in tatters. But, there’s a simple, natural solution that can help you keep these voracious insects at bay.
The answer may be closer than you think, hiding in plain sight within your herb garden. This easy-to-grow herb helps to repel Japanese Beetles and protect your garden from their destructive appetite.
What is Catnip?
Catnip, scientifically known as Nepeta cataria, is a perennial herb belonging to the mint family (Lamiaceae). Catnip is a relatively easy herb to grow. It thrives in full sun and well-draining soil. It’s drought-tolerant and can self-seed easily, making it a low-maintenance addition to any garden.
It is native to Europe and Asia but has been naturalized in many parts of the world, including North America. The plant is characterized by its square stems, toothed leaves, and small, white or lavender flowers.
Why Catnip Repels Japanese Beetles
Several factors work together to make catnip a good Japanese beetle repellent:
- Nepetalactone: The essential oil nepetalactone, which is responsible for catnip’s effect on cats, is also thought to be the primary repellent for Japanese Beetles.(ref) Insects, in general, are sensitive to strong odors, and the intense aroma of nepetalactone is believed to overwhelm their olfactory senses, making the plant less attractive for feeding or laying eggs.
- Iridoid Glycosides: Besides nepetalactone, catnip contains other compounds called iridoid glycosides, which are known for their insect-repelling properties. These compounds can interfere with the insect’s nervous system or digestive system, making the plant unpalatable or even toxic to them.
- Strong Scent Masking: The strong minty scent of catnip may mask the attractive odors of nearby plants that Japanese Beetles typically feed on. This makes it harder for the beetles to locate their preferred food sources.
- Companion Planting: Catnip is often used in companion planting strategies, where it is grown alongside other plants susceptible to Japanese Beetles. The catnip’s repellent properties are believed to create a protective barrier around the neighboring plants, deterring the beetles from attacking them.
Using Catnip as a Beetle Repellent in Your Garden
Here’s how to incorporate catnip into your garden for beetle control:
Growing Catnip Plants
- Planting: Catnip thrives in full sun and well-draining soil. Plant it around the perimeter of your garden or near susceptible plants like roses, raspberries, and grapes, which are often targeted by Japanese Beetles.
- Maintenance: Catnip is a low-maintenance herb that requires minimal care. Water it regularly, especially during dry spells, and prune it occasionally to encourage bushy growth.
- Companion Planting: Catnip can be planted alongside other beetle-repelling plants like garlic, chives, and tansy to create a stronger defense against pests.
Using Dried Catnip
- Harvesting: Harvest catnip leaves and stems before flowering for the strongest scent. Hang them to dry in a cool, dark place.
- Crushing and Scattering: Once dried, crush the catnip and scatter it around plants susceptible to beetle damage. Reapply after rain or watering.
- Catnip Spray: Make a catnip spray by steeping dried catnip in hot water. Let it cool, strain, and spray it directly on plants.
Additional Tips
- Start catnip indoors from seed six to eight weeks before the last frost.
- Transplant seedlings outdoors after the last frost when they have at least two sets of true leaves.
- Catnip can be invasive, so consider growing it in containers to control its spread.
- Reapply dried catnip or spray regularly, especially after rain or watering, to maintain effectiveness.
- Combine catnip with other beetle control methods like handpicking, traps, and row covers for best results.
While catnip is effective for repelling Japanese Beetles, its effectiveness may depend on the beetle population and environmental conditions. It is always best to use a combination of methods for optimal pest control in your garden.
If Japanese beetles are rampant, seek professional help.
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Nancy has been a plant person from an early age. That interest blossomed into a bachelor’s in biology from Elmira College and a master’s degree in horticulture and communications from the University of Kentucky. Nancy worked in plant taxonomy at the University of Florida and the L. H. Bailey Hortorium at Cornell University, and wrote and edited gardening books at Rodale Press in Emmaus, PA. Her interests are plant identification, gardening, hiking, and reading.