The short answer: no, cedar trees do not attract mosquitoes. Cedar wood and cedar oil actually contain compounds that mildly repel insects. But there is a real reason this question keeps coming up — and it has nothing to do with the cedar species itself. It has to do with the micro-environment that dense cedar hedges create in your yard. Here is the honest answer, including what is true, what is myth, and what actually matters for mosquito control.
Why People Think Cedars Attract Mosquitoes
This belief is widespread among GTA homeowners, and it almost always traces back to the same observation: "Whenever I walk past my cedar hedge, I get swarmed by mosquitoes." That observation is real. The conclusion drawn from it — that the cedar is somehow attracting mosquitoes — is wrong, but the experience is not.
What is actually happening is more subtle and more useful to understand. Mosquitoes do not behave the way most people imagine. They are not actively flying around looking for prey for most of the day. They are resting — and your cedar hedge is one of the best resting environments on your property.
The Real Science: Cedar Oil Repels Insects
Cedar wood (eastern white cedar, Thuja occidentalis, the species most commonly used for hedges across the GTA) contains aromatic compounds including thujone, thujaplicins, and cedrol. These compounds are well-documented insect deterrents — which is why cedar chests and cedar closets have been used for centuries to protect wool and fabric from moths and other insects.
Cedar oil is also a registered active ingredient in some commercial mosquito and tick products, used specifically because of its mild repellent properties. So if cedar were going to do anything to local mosquito populations, the effect would be slightly repellent — not attractant.
The catch: the amount of these aromatic compounds released by a living cedar tree into the surrounding air is extremely small. Far too small to create a meaningful repellent zone in your yard. You cannot solve a mosquito problem by planting cedars. But you also cannot create one by planting cedars.
What Actually Happens: Cedars Create Resting Habitat
Mosquitoes spend the majority of their adult lives resting, not flying. They are not strong fliers. They are not heat-tolerant. They cannot survive direct midday sun for long. To get from one feeding bout to the next, they need a refuge that meets very specific conditions:
- Shade — direct sun dehydrates and kills resting mosquitoes
- High humidity — mosquitoes lose body water rapidly in dry air
- Low air circulation — mosquitoes are easily dislodged by wind
- Vertical structure — they prefer to perch on leaves and branches, not ground
- Cool temperature — slightly cooler than the open yard
A dense, untrimmed cedar hedge meets every one of these requirements. The interior of a 2-metre cedar hedge can be 5–8°C cooler than the open lawn on a hot summer afternoon, with substantially higher humidity and almost no air movement. From a mosquito's perspective, that is a five-star hotel.
This is also why mosquitoes seem to swarm out of cedar hedges when you brush past them. They are not attracted to you walking by — they were already there, sheltering from the heat, and your movement disturbed the canopy. The same thing happens with dense yew hedges, juniper screens, and tightly-branched boxwood — but cedars are by far the most common privacy hedge in GTA yards, so they get blamed disproportionately.
Cedar Hedge vs Cedar Tree: A Critical Distinction
Not all cedars create resting habitat. The structural density and pruning matters enormously.
A specimen cedar tree on a lawn
A single cedar tree growing in open lawn — pyramidal in form, with daylight reaching most of the canopy and good air circulation around the trunk — provides almost no useful resting habitat for mosquitoes. The interior is too exposed, too dry, and too breezy. These trees do not increase mosquito pressure.
A trimmed cedar hedge with open structure
A well-maintained cedar hedge that has been pruned to keep the interior open, with dead inner branches removed and good vertical air circulation, provides only modest resting habitat. Mosquitoes will use the outer foliage but not in heavy concentrations.
A dense, untrimmed cedar hedge with leaf litter at the base
This is the worst case. A 2-to-3-metre cedar hedge that has been allowed to grow into itself, with a dense interior of dead branches, leaf and needle litter accumulated at the base, and limited air movement, can shelter remarkable numbers of mosquitoes. On a hot July afternoon, hundreds of mosquitoes can rest in a 10-metre stretch of dense hedge — only to come pouring out at dusk to feed on whoever is sitting on the patio.
Other Yard Features That Create Resting Habitat
Cedar hedges are not unique. Any dense vegetation creates similar conditions. The same daytime resting behaviour applies to:
- Yew hedges (Taxus)
- Boxwood and dense privet
- Juniper screens
- Mature ornamental beds with thick ground cover (hosta, ferns, ivy)
- Tall ornamental grasses
- Areas under decks and porches
- The undersides of low-skirted patio furniture
- Compost bins, woodpiles, and garden sheds
If you can identify the resting habitats on your property, you can target them. This is exactly what professional barrier spray does — and why the application technique matters as much as the product itself.
What to Do About Your Cedar Hedge (Without Removing It)
You do not need to rip out your cedars. They provide privacy, wind protection, wildlife habitat, year-round colour, and significant property value. Removing a mature cedar hedge to fix a mosquito problem is like demolishing your kitchen because you have ants. Manage instead.
1. Open up the interior
Have your cedars professionally pruned every 2–3 years to remove dead inner branches and create some vertical air movement. This reduces both mosquito habitat and the risk of disease in the cedar itself (cedar leaf blight thrives in the same conditions).
2. Clear the base
Remove accumulated needle litter, leaves, and debris from the base of the hedge each spring. This is also a major mosquito (and tick) hiding zone.
3. Improve drainage
Make sure the soil at the base of the hedge is not retaining standing water after rainfall. Re-grade or add mulch as needed. Standing water at the base of dense vegetation is a double problem: a breeding source and a resting refuge stacked together.
4. Apply professional barrier spray
This is the highest-leverage step. A properly applied professional mosquito spray treats the underside and interior canopy of dense vegetation — exactly the surfaces where mosquitoes rest. The Health Canada–approved residual formula remains active for several weeks, killing mosquitoes that come into contact with the treated foliage. We focus heavily on cedar hedges, ornamental beds, and the lawn-bed transition zone for this reason.
5. Limit other resting habitat too
While you are at it, address the rest of the resting micro-environment on the property: trim back overgrown shrubs, clear leaf litter from garden beds, and check our hidden mosquito breeding spots guide for the standing-water sources that are quietly producing mosquitoes alongside your hedge.
Are There Plants That Actually Repel Mosquitoes?
Yes — but the effect is small and localized. Several plants release low levels of mosquito-deterrent compounds when their leaves are crushed, brushed, or warmed in direct sunlight:
- Citronella grass — modest repellent, requires direct contact with leaves
- Lemongrass — same active compound as citronella
- Lavender — pleasant scent, mild repellent effect
- Basil — some research supports mild repellent effect
- Catnip — the active compound (nepetalactone) has demonstrated repellent activity in lab studies
- Marigolds — long believed to repel insects, modest evidence
- Rosemary — aromatic, mild repellent
These plants are worth growing — they look good, smell good, and contribute marginally to a less-attractive yard. But they will not solve a mosquito problem on their own. The realistic role for mosquito-repelling plants is around outdoor seating areas, where you can brush against the leaves and release the oils, combined with broader barrier spray treatment on the rest of the yard.
The Big Picture: It Is Not the Plant, It Is the Habitat
Cedar trees are not the enemy. They are not attracting mosquitoes any more than a parking garage is attracting cars. What is actually happening is that dense, undisturbed vegetation provides the daytime shelter mosquitoes need to survive between feeding bouts. The plant species barely matters. The structure does.
Manage the structure — open up dense plantings, clear leaf litter, improve drainage, and treat the underside of resting habitat with a professional barrier spray — and your cedar hedge becomes a feature of your yard rather than a refuge for the insects that ruin your evenings on it.
Get Your Yard Treated Properly
If you have cedar hedges, dense ornamental beds, or any of the other structural mosquito refuges discussed in this article, a properly applied barrier spray makes a substantial difference. Book a free yard assessment and we will walk the property, identify the rest zones, and give you an honest quote for treatment. We service 19 cities across the GTA — most new customers can be scheduled within the same week during the season.