How to Keep Mice Out of Your Garden: A Practical Guide for Canadian Gardeners

TL;DR

• Use a physical barrier of metal mesh with openings no wider than about 1/4 inch (6 mm). Mice chew through plastic netting, rubber and wood.
• Check whether you have mice or voles. They need slightly different fixes, and the rodent chewing your carrots may well be a vole.
• Take away food and cover: harvest promptly, pick up fallen fruit, cover compost scraps, clean up spilled bird seed and mow around your beds.
• Lining raised beds with hardware cloth, covering seed beds until seedlings are established and putting hardware cloth guards on young trees in fall can all help.
• Don't rely on mint, peppermint oil, ultrasonic stakes or cats. They often do little to keep mice out of a garden on their own.
• Need help? Get a quote from a recommended local exterminator through Pest Agent's referral form.

Keeping mice out of a garden gets harder when you are not sure a mouse is to blame. The rodent chewing your carrots, or girdling young trees under the snow, is often a vole, and voles and mice call for slightly different fixes.

Both respond to the same pull, though. A bed full of seed, heavy mulch and fallen produce draws them in, and a border of scented plants or an ultrasonic stake has little evidence of keeping them out. The fastest way to know which animal you have is to read the clues it leaves in the soil and on your plants.

How Can You Tell Mice Are in Your Garden?

Mice in your garden usually reveal themselves through dug-up seeds, nibbled produce, droppings and small burrows long before you see one. Many garden rodents are active at night, so the damage is often the only clue. Check your beds in the morning, when fresh signs are easiest to spot.

Dug-Up Seeds

Dug-up seeds are often the first sign of mice in a garden. Deer mice mainly eat seeds, and UC IPM notes they dig up planted seeds such as melon and feed on seeds sown in rows. If whole rows of peas, corn, squash or sunflowers fail to come up and you find small holes where the seeds were, mice are a likely cause. Birds also take seeds, though, so look for droppings and tracks before you decide who the culprit is.

Droppings

Droppings are the easiest way to confirm mice. According to HealthLinkBC, mouse droppings are about 6 mm (1/4 inch) long and oval, while rat droppings are larger. Look along bed edges, under boards, inside the compost bin and around bird feeders.

Burrows and Runways

Burrows and runways point to voles more than mice. Voles often leave narrow paths through the grass that link burrow openings about 1-1/2 to 2 inches (about 4 to 5 cm) across (UC IPM). They often feed on vegetables such as carrots, beets, lettuce and tomatoes, and they may eat bulbs and tubers underground.

Gnawed Bark

Gnawed bark at the base of young trees and shrubs is a classic winter sign in Canada. The City of Calgary explains that voles work under the snow and can kill or badly injure trees and shrubs by chewing all the way around the stems and roots, called girdling. Young, thin-barked plants are most at risk, and you usually only see the damage when the snow melts.

Mice Versus Voles

Mice and voles need slightly different fixes, so it helps to know which one you have.

• Voles are compact and heavy-set, with small eyes, small ears, a short tail and greyish-brown fur. They tend to live in runways and burrows outdoors and usually do not enter homes.
• Deer mice typically have large eyes and ears, a white belly and white feet, and a tail that is dark on top and white underneath (UC IPM). They are the mice most often found in sheds, woodpiles and cottages in Canada.
• House mice are grey to light brown with an almost hairless tail. They live outdoors in summer but often move into buildings in autumn as nights get colder (UC IPM).

Our mice identification chart covers more species found in Canada.

Why Are There Mice in Your Vegetable Garden?

Mice in a vegetable garden are there for two things: food and cover. A garden with seeds in the ground, ripe produce, a compost pile and long grass nearby gives them everything they need. UC IPM notes that good sanitation alone seldom gets rid of mice, but poor sanitation draws them in and lets them thrive in greater numbers, so removing food and cover is the base that every other method builds on.

Seeds and Fallen Produce

Seeds and fallen produce are a free meal for mice. Harvest ripe vegetables promptly, pick up fallen fruit and nuts (HealthLinkBC), and clear out spent plants and unharvested crops at the end of the season. Store seed packets, bulbs and bags of bird seed in metal or heavy plastic containers with tight lids, not in a cardboard box in the shed.

Compost Bins

Compost bins attract mice when food scraps sit uncovered. HealthLinkBC recommends covering food scraps in backyard compost, especially cooked food, meat and bones, rotating the compost and using a pest-proof container. An open pile is hard to protect. A closed bin with a lid, set on a base of metal mesh with openings no wider than 1/4 inch (6 mm), can help keep mice from tunnelling in from below.

Bird Feeders

Bird feeders drop a steady supply of seed onto the ground. HealthLinkBC advises fitting feeders with trays and cleaning up spilled seed often. Move feeders away from your vegetable beds, and do not leave pet food outside overnight.

Tall Grass and Weeds

Tall grass and weeds can give mice and voles cover from hawks, owls and cats. Mow the lawn around your garden regularly and keep a strip of short grass or bare ground between the lawn and your beds. The City of Calgary recommends keeping grass-free areas around trees, shrubs and gardens, because tall grass can be ideal vole habitat.

Heavy Mulch

Heavy mulch gives voles and mice a hidden place to feed. UC IPM lists heavy mulch and dense ground cover among the things to remove where voles are a problem. You can still mulch: keep it thin, and pull it back from stems and tree trunks, especially before winter.

Woodpiles

Woodpiles, lumber and clutter make perfect nesting spots. HealthLinkBC recommends storing lumber and firewood on stands off the ground and removing unused piles. Keep them away from your house and your garden beds. Sheds can become a nesting site too, so read our guide to keeping mice out of your shed.

How to Keep Mice Out of Your Garden With Barriers

Keeping mice out of your garden usually works best with a physical barrier of metal mesh with openings no wider than 1/4 inch (6 mm). UC IPM calls exclusion the most successful and permanent way to control house mice, and notes that they can squeeze under gaps of about 1/4 inch. Use galvanized hardware cloth (a stiff welded wire mesh). Plastic netting, rubber and wood are usually not enough, because mice can chew through them.

Hardware Cloth Fencing

Hardware cloth fencing protects a whole bed or a small garden. For voles, UC IPM recommends wire fencing at least 12 inches (about 30 cm) above ground, with mesh of 1/4 inch (6 mm) or smaller, and the bottom edge buried about 6 to 10 inches (15 to 25 cm) deep so they usually cannot tunnel underneath. Check the fence each spring for gaps at corners and gates, and keep grass and weeds from growing against it, since plants can act as a ladder.

Lining Raised Beds

Lining raised beds stops mice and voles from coming up from below. Before you fill a new bed, lay hardware cloth across the bottom and fasten it to the inside of the frame so there are no gaps along the edges. For an existing bed, you can do the same when you next replace or turn over the soil. This can be one of the most effective fixes for a vegetable garden, because it protects roots, bulbs and seeds at the same time.

Covering Seed Beds

Covering seed beds protects the stage when mice do the most damage. Oregon State University Extension suggests covering beds with rigid hardware cloth or tightly stretched netting until seedlings are established. A simple frame of hardware cloth laid over the row after sowing keeps out both mice and birds. Remove it once the plants are big enough that losing a few leaves no longer matters.

Tree Guards

Tree guards protect young fruit trees and shrubs from winter girdling. The City of Calgary recommends cylinders of hardware cloth with mesh of a quarter inch or less, buried about 2 to 3 inches (5 to 8 cm) into the soil and reaching about 2 inches (5 cm) above the expected snow line. Put them on in fall, before the first snow, and check them each spring.

Do Repellents, Plants and Cats Keep Mice Away?

Repellents, scented plants and pets usually do little to keep mice out of a garden on their own. They are popular because they are easy, but extension research shows they are not a substitute for barriers, less cover and traps.

Mint and Peppermint Oil

Mint and peppermint oil are the most common home remedies, but we found no government or university source showing that they keep mice out of a garden. UC IPM states that chemical repellents are not effective enough against deer mice to justify their cost. Planting mint around your beds will not hurt, but keep it in pots, since it spreads quickly, and do not rely on it to protect your seeds.

Ultrasonic Repellers

Ultrasonic repellers, including solar garden stakes, have very limited use. UC IPM explains that ultrasonic sound is directional, does not go behind objects and fades quickly with distance, and that there is little evidence sound, magnetic or vibration devices drive mice away. HealthLinkBC adds that they may work at first but do not have long-term success. If you want to compare products for indoor use, see our review of the best mouse repellers.

Spray Repellents

Spray repellents for rodents are meant for bark and shrubs, not food plants. Canadian products such as bittering sprays are labelled for outdoor surfaces and must never be used on food, edible plants or fruit. UC IPM and the City of Calgary both say repellents have limited or questionable effectiveness on their own and are best applied before damage starts. Always read the label before you use one.

Cats

Cats catch some mice, but they rarely control a garden mouse problem. UC IPM notes that there are few situations where cats or dogs keep rodent numbers down, and that predators can make mice more secretive, which gives a false impression that the problem is solved. Owls and hawks eat voles too, but UC IPM says they rarely bring numbers down to acceptable levels on their own.

How Do You Get Rid of Mice Already in Your Garden?

Getting rid of mice already in your garden starts with traps, which Health Canada calls the first line of defence against mice and rats. Combine trapping with the barrier and cleanup steps above, so new mice do not simply replace the ones you catch.

Snap Traps

Snap traps are the simplest and safest way to remove garden mice. HealthLinkBC recommends traps to get rid of mice and suggests baiting them with dried fruit, peanut butter mixed with oats, or cheese. Wear gloves when you handle traps and dead mice, as UC IPM advises, and double bag them before you put them in the garbage. Our step-by-step guide shows how to set a mouse trap, and our tests of the best mouse traps compare the main types.

Trap Placement

Trap placement outdoors must protect birds, pets and children. Put traps inside a covered box or a short length of pipe, or use tunnel traps or trap covers as the City of Calgary suggests, so mainly small rodents can reach the trigger. Place them along bed edges, fences and runways, with the trigger end in the runway. UC IPM notes that house mice seldom travel more than 30 feet (about 9 metres) from their nest, so space traps no more than about 10 feet (about 3 metres) apart where you see activity. For voles, even a small garden may need about a dozen traps.

Live Traps

Live traps are not a good long-term answer for garden mice. UC IPM reports that released mice may find their way back or die from exposure or predators in an unfamiliar area. If you use live traps, check them often.

Rodent Poison

Rodent poison is a last resort in a garden. HealthLinkBC advises against using poison around the home, because poisoned rodents can die where you cannot find them, and the National Pesticide Information Center warns that baits can be dangerous to kids, pets and wildlife. Owls, hawks and other animals can also be poisoned by eating a poisoned mouse. If you do use one, Health Canada rules mean that homeowner (domestic class) rodenticides must be solid blocks used in a bait station, and the strongest second-generation anticoagulants (brodifacoum, bromadiolone and difethialone) are not allowed in homeowner products. British Columbia goes further and restricts the sale and use of second-generation rodenticides, according to the Government of British Columbia. Choose a product with a PCP number on the label, follow the label exactly, and never place bait in or next to your vegetable beds.

Safe Cleanup

Safe cleanup matters most in garden sheds and outbuildings. In Canada, hantavirus has been found only in deer mice, and HealthLinkBC names garden sheds among the places people are exposed. The virus spreads when dust from droppings, urine or nests is breathed in, so never sweep or vacuum droppings. Instead:

1. Open doors and windows and let the shed air out for 30 minutes before you go in.
2. Wear rubber gloves, goggles and a well-fitting mask such as an N95; Health Canada advises gloves and a mask.
3. Pour diluted bleach (1 part bleach to 9 parts water) or a household disinfectant on the droppings and nesting material, as UC IPM advises, without using a sprayer.
4. Let it soak for 10 minutes, then wipe it up with paper towels.
5. Double bag the waste, seal the bags and wash your gloves before taking them off.

Our guide on how to clean mouse droppings covers indoor cleanup in more detail.

When to Call a Pest Control Professional

Calling a pest control professional makes sense when mice keep coming back despite barriers and traps, when a large vole outbreak is girdling trees, or when you find droppings and nests in a shed or under your deck. HealthLinkBC and the Government of British Columbia both recommend a licensed pest control company if you cannot control rodents on your own. A professional can inspect your yard and the outside of your house, find nesting areas and entry points, and set tamper-resistant exterior bait stations or traps where they are safe.

Garden mice often move into the house in fall, so also read how to keep mice out of your house. If you want help, you can get a quote from a recommended local exterminator through Pest Agent's referral form, or check our guide on when to call a mouse exterminator. For everything else about mice, visit our mice hub.