Every spring, homeowners share a folk remedy for lawn grubs: scatter pennies on the soil and the grubs will go elsewhere. The tip has a grain of truth behind it, because copper compounds do fight some garden pests, but modern pennies no longer carry enough copper to matter, and grubs are insects that feed underground out of reach of any coin. Master gardeners who field the question agree that pennies do not deter grubs, and the change is better spent on methods with evidence behind them, such as beneficial nematodes and milky spore powder. Building healthy soil is the real defense, and mulching a garden bed for healthier plants and soil does more for a lawn than a pocketful of scattered coins.
This article separates the penny myth from what actually works: the grub life cycle, non-toxic control options, soil health as prevention, how to confirm an infestation, and a seasonal routine that keeps lawns ahead of the damage.
The Penny Myth: Why Copper Coins Do Not Deter Grubs
The idea that pennies repel grubs comes from copper’s reputation as a pest deterrent. Copper strips have a long history of use against slugs and snails, and copper compounds appear in some garden fungicides, so the leap to grubs seems reasonable at first glance. The jump falls apart on two facts: grubs live in the soil feeding on roots, and modern pennies contain almost no copper.
What modern pennies are made of
Pennies minted after 1982 are 97.5 percent zinc with a thin copper plating, and the plating makes up only about 2.5 percent of the coin’s weight. A few pennies scattered on the surface release essentially no copper into the soil, and even if they did, the metal would not reach the grubs feeding on roots several inches down.
Why the myth persists
Folk garden advice survives because it is cheap, harmless, and easy to share. A handful of pennies costs less than a box of insecticide, does no obvious damage, and gives the gardener a sense of action. The problem is the opportunity cost: time spent scattering coins is time not spent aerating, watering correctly, or applying a control that actually works.
The same skepticism serves indoors. Beginners who choose simple houseplant species that thrive with minimal care learn quickly that reliable results come from matching the plant to the conditions, not from tricks, and the same principle applies to the lawn.
What Grubs Are and How They Damage Lawns
Grubs are the larval stage of beetles. Japanese beetles, June beetles, and European chafers lay eggs in the soil in summer, the eggs hatch into C-shaped white grubs that feed on grass roots through late summer and fall, and the grubs move deeper to overwinter before pupating and emerging as adults the following year. A heavy population can eat enough root mass to kill the grass in patches.
Recognizing grub damage
- Brown or yellow patches that appear even with regular watering
- Turf that lifts like a loose carpet because the roots are gone
- Skunks, raccoons, and birds digging and pecking at night for the grubs
- Spongy turf that rolls back easily when pulled by hand
The damage window matters. Grubs feed most aggressively in late summer and early fall, so a lawn that looks fine in July can collapse by September. Inspect suspect areas in August, when the grubs are large enough to see.
Plants defend gardens in other ways too. Some plants that keep mosquitoes away repel biting insects with scented oils, a reminder that the right plant selection can reduce pest pressure without sprays, whether the pest flies or crawls.
Proven Grub Control Methods
When the penny trick fails, three approaches actually work: beneficial nematodes, milky spore, and, for severe cases, targeted insecticides. The first two are non-toxic to pets and pollinators, which is why they are the preferred starting point.
Beneficial nematodes
Nematodes are microscopic worms that enter grub larvae and release bacteria that kill them. They work best when soil temperatures sit between 55 and 70 degrees Fahrenheit, typically late summer or early fall, and they need the soil kept moist for a week or two after application so the worms can move. One application treats the current generation of grubs.
Milky spore
Milky spore is a bacterium that infects Japanese beetle grubs specifically and builds up in the soil over several seasons. It takes two to three years to reach full effectiveness, which makes it a long-term strategy rather than an emergency fix, but established spores can protect a lawn for a decade or more.
Application timing
- Confirm grubs with a dig test before spending money on any product.
- Apply nematodes in late summer when soil is warm and grubs are small.
- Water the lawn lightly before and after application to help the product reach the roots.
- Apply milky spore in spring or fall, following the label’s coverage rate.
- Recheck the lawn in three weeks; live grubs mean the treatment needs another pass.
A note on chemical controls: they kill grubs quickly but also hit beneficial soil insects, so reserve them for confirmed infestations above the treatment threshold.
Pest pressure comes from all directions in a garden, and each pest needs its own strategy. The fencing, plants, and repellents that keep deer out of a garden work because they match the animal’s behavior, and grub control works the same way: choose the method that matches the pest’s life cycle.
| Method | What it targets | Timing | Pet safety | Cost |
|---|---|---|---|---|
| Beneficial nematodes | All common grub species | Late summer, soil 55-70 F | Safe | $15-$50 |
| Milky spore | Japanese beetle grubs | Spring or fall, repeat seasons | Safe | $30-$60 |
| Chemical insecticide | All grub species | Mid-summer to early fall | Keep pets off until dry | $15-$40 |
| Pennies | No effect | Any time | Safe | Wasted money |
Prevention Through Soil Health
Grubs prefer compacted soil, and the strongest prevention is a lawn that grows dense, healthy roots. Aerating, adding compost, and watering deeply all make turf less hospitable to grub damage.
Aerate compacted soil
Core aeration pulls plugs of soil out of the lawn, opening space for air, water, and roots. Aerate in the fall or spring when the lawn is actively growing, and follow with compost or topdressing so the holes fill with organic matter rather than closing back up.
Feed the soil with compost
Compost improves soil texture and feeds the microorganisms that support grass roots. For a targeted boost, brewing compost tea for richer garden soil delivers soluble nutrients and beneficial microbes straight to the root zone, and regular applications build the kind of soil structure grubs avoid.
Water and mow for deep roots
- Water deeply and less often so roots grow downward instead of staying shallow.
- Mow at 3 inches or higher to shade the soil and hold moisture.
- Leave grass clippings in place to recycle nitrogen back into the lawn.
- Avoid over-fertilizing in spring, which feeds top growth over roots.
Confirming an Infestation and Repairing the Lawn
Before buying any control, confirm that grubs are actually the problem. The damage patterns above can also come from drought, disease, or other insects.
The dig test
- Cut a 1-square-foot section of turf about 3 inches deep with a shovel.
- Fold the turf back like a carpet flap.
- Count the C-shaped white grubs in the soil and among the roots.
- Treat if you find 10 or more grubs per square foot; fewer usually needs no action.
Repairing damaged turf
Rake out the dead grass, loosen the top inch of soil, and overseed with a mix matched to the site’s sun exposure. Keep the seedbed moist until germination, and hold off on herbicides so the new grass establishes cleanly. Lawns that recover need about four to six weeks of consistent moisture before the new grass can be mowed normally. While the lawn recovers, beds that thinned out over the season can be refreshed by dividing ornamental plants for residential landscaping projects, which restores vigor to crowded perennials and fills bare spots with divisions you already own.
Building a Grub-Resistant Lawn Routine
A grub-resistant lawn is the product of a calendar, not a single treatment. The routine below repeats year after year and keeps grub pressure low enough that controls are rarely needed.
A seasonal calendar
- Spring: core aerate, overseed thin areas, and apply milky spore if building long-term protection.
- Summer: water deeply and watch for adult beetles laying eggs in July.
- Late summer: run the dig test and apply nematodes if the threshold is passed.
- Fall: reseed bare patches, keep mowing at 3 inches, and let leaves stay as mulch.
- Winter: leave the lawn longer and keep traffic off frozen turf.
Test the soil before you amend
Every amendment decision starts with a soil test. The same soil composition and quality management that grows productive tomato plants drives healthy turf: the right pH, organic matter, and nutrient balance produce roots that tolerate stress, and stress-tolerant grass is the one that shrugs off grub feeding.