Do Chestnuts Keep Spiders Away? Separating Fact From Fiction

The claim that horse chestnuts (conkers) repel spiders is one of the most widespread pieces of folk wisdom in pest control. People across the UK, Europe, and parts of North America swear by placing conkers on windowsills and near doors to keep spiders out. But is there any truth to it?

The Claim

The traditional advice is simple: place horse chestnuts near windows, doors, and in corners where spiders appear. The chestnuts supposedly emit a chemical that spiders find repulsive, keeping them from entering those areas.

What the Science Says

The scientific evidence for chestnuts as spider repellents is, frankly, very weak:

• No peer-reviewed study has demonstrated that whole horse chestnuts repel spiders.
• A 2010 study by the Royal Society of Chemistry found no evidence that chestnuts placed in a room deterred spiders.
• Horse chestnuts do contain saponins (triterpenoid saponins), which have some documented insecticidal properties. However, these compounds are contained within the nut and are not released into the air in meaningful quantities from whole, unbroken chestnuts.
• A student project at the University of Bristol found inconclusive results, with spiders showing no significant aversion to chestnuts.

Why the Myth Persists

Several factors explain why people believe chestnuts work:

• Timing: In the Northern Hemisphere, horse chestnuts fall in autumn — the same time spider sightings naturally increase as males wander during mating season. People place chestnuts out, the spider activity eventually subsides (as it would anyway), and the chestnuts get the credit.
• Confirmation bias: People who believe chestnuts work notice when they do not see spiders, but overlook times when spiders appear despite the chestnuts.
• Low cost, low risk: Because chestnuts are free and harmless, people are willing to try them. Even if they do not work, there is nothing lost.

Other "Spider Repellent" Folk Remedies

Chestnuts are not the only folk remedy lacking scientific support. Several other commonly recommended items fall into the same category:

Hedge Apples (Osage Orange)

Osage orange fruits are often placed in basements and garages to repel spiders. Research has found that compounds within Osage orange fruit do have insecticidal properties, but only when concentrated and extracted. Whole fruits sitting on a shelf release negligible amounts of these compounds into the air. The effect on spiders is minimal to nonexistent.

Tobacco

Some sources recommend soaking tobacco in water and spraying the solution around the home. While nicotine is indeed toxic to many arthropods, homemade tobacco preparations have inconsistent concentrations and pose health risks to children, pets, and even adults through skin absorption. This method is not recommended.

Cedar Chips and Blocks

Cedar contains natural oils that repel some insects (particularly moths), and this reputation has extended to spiders. While cedar may deter some insects from storage areas, there is little evidence it significantly repels spiders.

Lemon and Citrus Peels

Rubbing citrus peels along windowsills is another common recommendation. The limonene in citrus oils does have documented insecticidal properties, but the amount released from rubbed peels is small and fades quickly. Essential oil sprays containing concentrated citrus oil are a better option if you want to use citrus as a deterrent.

Should You Try Chestnuts?

There is no harm in placing horse chestnuts around your home. If it makes you feel better, go for it. Just do not rely on them as your primary spider control strategy. The same applies to hedge apples, cedar blocks, and citrus peels — they are harmless additions but should not replace proven prevention methods.

What Actually Works

Instead of chestnuts, focus on proven methods:

• Peppermint oil: Has actual scientific support as a spider deterrent.
• Essential oils: Tea tree, eucalyptus, and lavender have some documented repellent properties.
• Diatomaceous earth: Kills spiders that contact it.
• Sticky traps: Physically catch spiders.
• Sealing entry points: Prevents spiders from entering in the first place.
• Reducing prey insects: Eliminates the main reason spiders come inside.

For a comprehensive approach, see our natural spider repellents guide, spider prevention tips, and how to get rid of spiders.

Expert Insights

I have been asked about using horse chestnuts (conkers) to repel spiders many times in my 15 years as a pest management professional. While I understand the appeal of a natural remedy, I have never seen any reliable evidence that chestnuts repel spiders. In controlled settings, I have placed chestnuts near spider habitats with no observable deterrent effect. I always steer clients toward proven IPM strategies instead. — Sarah Mitchell, BCE

Sources and References

• Ohio State University Extension
• University of California Riverside Spider Research
• Burke Museum of Natural History and Culture

How to Identify

Identifying a real spider problem - as opposed to a manageable seasonal increase - is essential before investing in any repellent strategy. Signs of a genuine indoor spider issue include finding multiple live spiders weekly, discovering egg sacs in living spaces, or consistently seeing webs in high-traffic areas. Seasonal increases in autumn are normal and reflect males wandering during mating season; they are transient and self-limiting. If you are seeing clusters of webs in corners, basement walls, or behind storage items, focus on the underlying conditions - moisture, prey insects, and entry points - rather than surface remedies. Identify the spider species involved, since harmless house spiders require a different response than medically significant species such as brown recluses or black widows, for which no folk remedy provides adequate protection.

Risk and Severity

The primary risk associated with relying on unproven remedies like chestnuts is opportunity cost: time spent on ineffective measures is time not spent on proven strategies. For nuisance species, this means tolerating a persistent spider population longer than necessary. For medically significant species such as black widows or brown recluses, relying on folk remedies instead of targeted exclusion and professional treatment creates genuine bite risk. No scientific evidence supports chestnuts as a spider deterrent. Ohio State University Extension and other cooperative extension services have explicitly noted the lack of evidence for chestnut-based repellents and redirect homeowners toward mechanical exclusion and habitat modification as the evidence-based alternative.

Solutions and Actions

Replace folk remedies with proven control methods. Apply food-grade diatomaceous earth in cracks, crevices, and along baseboards where spiders travel. Use sticky traps along walls and in corners to capture and monitor the population. Apply a peppermint oil spray around entry points as a supplementary deterrent - this has more scientific backing than chestnuts. For persistent or high-density problems, apply a pyrethroid-based residual spray to foundation perimeter and interior crack-and-crevice areas. Remove webs and egg sacs promptly with a vacuum. These methods address the spider population directly rather than hoping for a chemical deterrent effect from a whole fruit sitting on a windowsill.

Prevention

Durable spider prevention does not involve placing objects around the home - it involves sealing the structural gaps that spiders use to enter. Caulk around window frames, door frames, and utility penetrations. Install door sweeps on all exterior doors. Reduce outdoor lighting near entry points by switching to yellow or sodium vapor bulbs. Clear ground-level debris, mulch, and vegetation from against the foundation. Reduce indoor prey insects through sanitation and screen maintenance. These measures, recommended by Penn State Extension and UC IPM, address spider entry at the source and do not require ongoing replacement the way folk remedies do.

Main Causes

Indoor spiders activity reflects two drivers — a hospitable indoor environment and a sufficient supply of insect prey. Spiders enter through gaps under doors, around windows, utility penetrations, and any opening leading to attics, basements, garages, or crawl spaces. Once inside they settle wherever undisturbed corners, low light, and easy prey access converge. Cooler weather pushes outdoor species inside in late summer and fall as they seek mating sites or shelter. The most important upstream driver is the indoor insect population — homes with active fly, gnat, moth, or other pest activity sustain larger spider populations than homes without prey. Cluttered storage areas, accumulated webbing, and outdoor lighting that draws nocturnal insects all amplify the indoor pressure.

Frequently Asked Questions

Do chestnuts really repel spiders?

There is no scientific evidence that chestnuts or horse chestnuts (conkers) repel spiders. This is a folk remedy that has been tested in informal experiments, including student science projects, with inconsistent and generally negative results. No peer-reviewed research supports this claim.

What natural remedies actually work against spiders?

The most effective natural approaches are habitat modification (reducing clutter, sealing entry points, removing outdoor debris) and reducing the prey insects that attract spiders. Some essential oils like peppermint may have short-term repellent effects, but no natural remedy is as effective as proper exclusion and sanitation.

Why do people think chestnuts repel spiders?

The belief likely originated as folk wisdom passed down through generations in Europe. Some have speculated that a chemical compound in chestnuts might repel spiders, but no such compound has been identified or demonstrated to have repellent properties in controlled studies.

What should I recheck first for chestnuts for spiders?

Recheck the exact place, timing, and repeated signs connected with chestnuts for spiders before changing your plan. A single sighting or old web can mean something very different from fresh activity in several rooms. Confirm whether insects, clutter, moisture, gaps, or stored items are supporting the issue, then match the response to what you actually found.