How to Get Rid of Ants in Your Garden Without Harming Your Plants

TL;DR

• Work in this order: remove the honeydew insects, block the ants from your plants, make the beds less comfortable, then bait the colony.
• Check for aphids first, since they are usually what the ants are after. A strong spray from the garden hose knocks them off.
• Band tree trunks with a sticky barrier on a wrap so it never touches young bark, and rake large mounds in beds every 2 days so the ants tend to move on.
• To kill the nest, put closed bait stations or stakes on the ant trails, out of reach of children and pets as UC IPM advises, don't spray, and leave them at least two weeks (Health Canada).
• Skip vinegar and boiling water in beds. Vinegar can damage any leaf or stem it touches, and boiling water can kill plant roots, usually not the colony.
• Need help? Get a quote from a recommended local exterminator through Pest Agent's referral form.

The usual advice on how to get rid of ants in the garden, a kettle of boiling water or a splash of vinegar, tends to hurt the plants more than the colony. Vinegar damages any green leaf it touches, boiling water kills roots, and neither one reaches a nest that sits deep underground.

Many gardeners also aim at the wrong target. A crowd of ants on a rose or a bean plant is often a sign of aphids, and the ants themselves may be doing the beds more good than harm.

Are Ants in Your Garden a Problem?

Ants in your garden are usually not a problem: Health Canada says they cause little damage in the garden and should be tolerated as much as possible, because they also eat other insects. There are over 100 species of ants in Canada (City of Calgary), and most of the ones you see in flower and vegetable beds are likely simply foraging. The trouble starts when they protect plant pests, build nests in the middle of your beds or pots, or sting.

How Ants Help Your Garden

Ants help your garden more than most gardeners think. According to the University of Saskatchewan, ants can prey on soft-bodied pests such as grubs, cutworms and caterpillars, their colonies can add organic matter to the soil and help plants take up nutrients, and some plants rely on ants to spread their seeds. Most ants usually do not eat plants or kill lawn or garden plants.

How Ants Protect Aphids

Ants protect aphids because they feed on honeydew, the sugary liquid aphids give off as they suck plant sap. UC IPM (University of California) explains that ants tend aphids, soft scales, whiteflies and mealybugs and fight off the ladybugs and other natural enemies that would eat them, so those pests can multiply and do more damage. A lot of ants climbing one plant is often a sign of an aphid problem, not an ant problem. Ants on peony buds are the exception: they generally neither harm nor help the flowers (University of Saskatchewan).

Signs Garden Ants Need Control

Garden ants need control when you see one of these signs:

• Steady trails of ants climbing stems, with aphids, sticky leaves or black sooty mould on the plant
• Ants nesting in a vegetable bed, a raised bed or a container, with loose, heaped soil around the roots
• Large nests that make beds or the lawn lumpy
• Ants that sting when you work the soil

If the ants are only crossing the garden, leave them alone. If they are coming into the house, our guide on how to get rid of ants outside covers the foundation and the perimeter.

European Fire Ants

European fire ants are the garden ants to take seriously in Canada. According to the Invasive Species Council of BC, this invasive ant (Myrmica rubra) arrived in British Columbia around 2010. Workers are red-brown, usually nest in soil without visible mounds, and can swarm and sting when a nest is disturbed. Do not try to dig out a nest yourself, and do not move soil, turf or leaf litter off your property, because that is how they often spread. For stinging red ants in general, see our guide to getting rid of red ants.

How to Get Rid of Ants in the Garden Step by Step

Getting rid of ants in the garden works best in this order: remove the honeydew insects, block the ants from your plants, make the beds less comfortable, then bait the colony. Each step is generally safe for plants, and the first ones often solve the problem on their own.

Check for Aphids

Checking for aphids comes first because they are usually what the ants are after. Look under the leaves and on new shoots of the plants where ants are climbing. Aphids are tiny, soft-bodied insects that often feed in clusters. Sticky, shiny leaves or a black coating on them (sooty mould growing on honeydew) usually mean honeydew insects are feeding.

Wash Aphids Off With Water

Washing aphids off with water is the gentlest fix. A strong spray from the garden hose knocks them off, and most dislodged aphids cannot climb back onto the plant (UC Master Gardeners). It also rinses off the honeydew that draws the ants. Spray in the morning so the leaves dry before evening, and repeat every few days while aphids are present. If water is not enough, switch to an insecticidal soap labelled for aphids.

Band Tree Trunks

Banding tree trunks keeps ants off fruit trees and shrubs. UC IPM recommends wrapping the trunk with heavy paper, duct tape or fabric tree wrap, then coating that collar with a sticky barrier product such as Tanglefoot, so the sticky material never touches young bark. Trim branches that touch fences, walls or other plants so the trunk is the only way up. Check the band every one to two weeks and stir the sticky layer, because dead ants and debris can form a bridge. For plant stands and small fruit trees, two-sided sticky tape can work the same way (City of Calgary).

Disturb Nests in Garden Beds

Disturbing nests in garden beds pushes the colony to move elsewhere without any product. The University of Saskatchewan suggests raking or shovelling large mounds about every 2 days to encourage the ants to move on. Health Canada adds that flooding a nest repeatedly with the garden hose drives the ants away. For mounds in the lawn, between patio stones or along the driveway, our guide to getting rid of ant hills goes into more detail.

Garden Bed Moisture

Garden bed moisture is another way to encourage ants to move on. The University of Saskatchewan recommends keeping lawns and gardens moist with daily watering for 7 to 10 days, then deep watering once a week, and mulching garden beds at least 10 cm (4 inches) deep. Setting your mower blade to its highest setting can also help keep the lawn thick around your beds.

Bait the Colony

Baiting the colony is the step that can kill the queen, and it is usually the most effective way to get rid of a nest you cannot live with. Worker ants carry the slow-acting bait back to the nest and share it, so the whole colony is poisoned, including the queens you never see (Health Canada, UC IPM). To bait safely in a garden:

1. Choose closed bait stations or bait stakes, not loose powders or liquids poured on the soil.
2. As UC IPM advises, place them near the ant trails and nest openings, on bare soil or a paver, not against the stems.
3. Keep them out of reach of children and pets.
4. Try two different baits at once, as Health Canada notes this gives better results.
5. Do not spray insecticides while you bait, or the ants will stop carrying bait home.

UC IPM notes that late winter and early spring, before colonies grow, is the most effective time to bait. In most of Canada, that means as soon as ants are active in spring.

How Long Baiting Takes

Baiting takes days to weeks, not hours. UC IPM says it can take 5 to 10 days to see fewer ants, and Health Canada recommends leaving baits out for at least two weeks and reapplying as needed. Replace empty stations, and if the ants ignore a bait, move it or switch products. Seeing more ants at first is normal: they are recruiting nest mates to the food.

When to Call a Pest Control Professional

Calling a licensed pest control professional makes sense if you suspect European fire ants, if the ants sting your family or pets, if nests sit against the foundation and the ants are coming indoors, or if several weeks of baiting have not helped. A professional can identify the species and use products and methods matched to it. You can get a quote from a recommended local exterminator through Pest Agent's referral form if you want help.

What Is the Best Plant Safe Ant Killer?

The best plant safe ant killer is a slow-acting bait inside a closed station, because the poison never touches the soil, the roots or the leaves, and it kills the colony instead of only the ants you see. Here is how the main options compare as an ant killer for garden use.

Ant Bait Stations

Ant bait stations are the first choice for gardens. The City of Calgary notes that slow-acting baits, such as boric acid baits, eliminate the colony and are generally low in toxicity to other animals. Outdoor bait stakes, which push into the soil, are made for beds and borders. For example, TERRO Outdoor Liquid Ant Bait Stakes contain 5.40% borax (sodium tetraborate decahydrate), but the manufacturer says they do not work on fire ants or carpenter ants. Check that the package lists the ants you have and that it is meant for outdoor use.

Borax Bait

Borax bait can work in a garden only if it stays inside a container. A Colorado State University Extension master gardener warns not to sprinkle borax directly on soil because it can stop plants from growing. The University of Saskatchewan advises against borax altogether where children, pets or small animals could eat it, and Health Canada says to keep baits out of their reach. Health Canada advises Canadians not to make homemade pesticides using boric acid, and borax can produce boric acid, so use a registered borate bait station or stake and keep it off the soil. Our guide to using borax to kill ants explains the registered options.

Diatomaceous Earth

Diatomaceous earth is a natural ant killer for plants that works by contact: the fine powder of crushed marine fossils scratches the ant's outer layer and dries it out (Health Canada, City of Calgary). Health Canada notes it remains active only as long as it is kept dry, so rain or watering can make it useless, and it can also kill beneficial insects such as ladybugs and bees. Use it in a thin line on ant trails and around nest openings, never on flowers, and avoid breathing the dust. The University of Saskatchewan treats it as a last resort near pets and small children. See our full guide to diatomaceous earth for ants.

Insecticidal Soap

Insecticidal soap is the plant safe way to treat the aphids that attract the ants. It is made from potassium salts of fatty acids and, as UC IPM notes for soap products, can kill on contact but leaves no residual toxicity. Safer's Insecticidal Soap, for example, is registered in Canada (PCP 14668) for aphids on houseplants, vegetables, fruit, shrubs and trees. Spray every surface of the leaves, including the undersides, and repeat as the label directs, since one application is rarely enough (Washington State University). The label also warns against using it on sweet peas, nasturtiums and delicate ferns.

Ant Killer Granules

Ant killer granules are the strongest ant killer for garden edges, but they are not plant safe in the same way. Granules are spread on nests or along a perimeter and kill the foraging ants that touch them, yet UC IPM notes that this kind of treatment does not kill the colony or the queens, so control is usually temporary. Canadian labels for pyrethrin granules such as Ortho Ant B Gon MAX warn that the product is toxic to bees and beneficial insects and require at least 7 days between applications. Keep granules away from vegetables and flowering plants, and never use them on top of a bait.

Reading the Label

Reading the label is what makes any ant killer safe. Health Canada advises checking that the product lists the pest and the place you want to treat, following every direction and warning, and looking for a PCP (Pest Control Products) number, which shows that Health Canada has approved it. Some provinces and municipalities restrict lawn and garden pesticides: Ontario, for example, bans their cosmetic use except for active ingredients on its Allowable List. If you have dogs or cats, our guide to pet safe ant killers compares the options.

Do Natural Ant Killers for Plants Work?

Natural ant killers for plants are a mixed bag: some are safe but only repel ants for a while, and others burn your plants or never reach the queen. Here is what the evidence says about the most popular home remedies.

Vinegar

Vinegar is a poor choice in a garden because it is a weed killer. UC IPM describes acetic acid, the acid in vinegar, as a non-selective contact herbicide, which means it can damage any leaf or stem it touches. It also usually kills only the ants it hits, and a Colorado State University Extension master gardener notes that vinegar and hot water often fail because nests are deep underground. If you want to know more, read does vinegar kill ants.

Boiling Water

Boiling water kills plant roots, not the colony. The University of Saskatchewan warns that it does not kill the queen, can scald you, and can kill the roots of nearby plants, and Health Canada says boiling water and detergent only reduce a colony temporarily. Keep it for cracks in a patio or driveway far from your beds, if you use it at all.

Coffee Grounds

Coffee grounds are a popular tip, but no extension service or study we found shows that they keep ants away. They are harmless to sprinkle on beds in small amounts, but do not count on them to move a nest.

Cinnamon

Cinnamon may cover the scent trail ants follow for a short time, but there is no evidence that it moves or kills a colony. It is safe for plants, so it is fine to try on a patio trail or a windowsill. Our guide on using cinnamon for ants explains what to expect.

Ant-Repelling Plants

Ant-repelling plants such as mint, lavender and tansy are often recommended, but the claims come from gardening sites, not from research. Be careful with tansy in particular: common tansy is designated a noxious weed under Alberta's Weed Control Act and contains compounds that are toxic to people and livestock in large amounts. If you like mint or lavender, grow them for their own sake, not as ant control.

Essential Oil Sprays

Essential oil sprays made with peppermint, orange or clove oil kill ants on contact, but UC IPM notes they have little lasting effect. They are fine for a trail on a patio table. On leaves, test a small area first and wait a day before spraying the whole plant.

How to Get Rid of Ants in Potted Plants

Getting rid of ants in potted plants is easier than in garden beds, because you can isolate the pot and treat it on its own. Health Canada notes that ants are drawn to the honeydew of aphids on houseplants, so check the plant for aphids first.

Signs of Ants in a Pot

Signs of ants in a pot include ants streaming out of the drainage holes when you water, small heaps of loose soil on the surface or around the base, and soil that seems hollow or sinks when you press it. Aphids or sticky leaves on the plant often go with them.

Soaking the Pot

Soaking the pot drives out or kills the nest without touching the rest of your garden. UC IPM suggests submerging the whole pot for 20 minutes or more in a bucket of water mixed with insecticidal soap. Use a soap registered for houseplants and follow the label for the mix, then let the pot drain fully.

Plant Stand Barriers

Plant stand barriers keep ants from climbing back. Health Canada suggests wrapping two-sided sticky tape around the legs of plant stands, and the same idea works on the outside of a pot or saucer. Keep pots from touching walls, railings or other plants, so the stand is the only way up.

Moving Potted Plants

Moving potted plants can move ants too. In British Columbia, the City of North Vancouver identifies infested potted plants, soil and mulch as a main way European fire ants spread. Check plants from friends or sales for ants before you bring them home, and do not share soil or pots from an area known to have fire ants.

For more ant guides, visit our ant hub.