Ants are great at teamwork. If you see them in or around your flowerpots it's very likely they may be planning to take it over. While they may not harm the plant physically, they may make it undesirable to bring the pot inside when weather gets cold. The solution is to get the ants out of the pot without having to discard your plant. There are several ways to accomplish this.
The use of diatomaceous earth, or DE, is effective in killing and repelling ants in flowerpots without causing any harm to your plants, according to ThrifyFun.com. DE is an organic and safe sediment composed of the skeletal remains of algae called diatoms. Sprinkle the DE dust around the base of the plant and on top of the soil. Ants should begin thinning out within 30 minutes of the application. You can buy DE at gardening centres or order it online.
You may choose to use boric acid as an ant pesticide if you are sure no pets or children will come into contact with it. This substance will not likely damage your plants, but it is poisonous if ingested, according to HarvestWizard.com. You can make your own boric acid ant bait by dissolving 1 tsp of boric acid powder and 10 tsps. of sugar into two cups of water. Soak cotton balls in the solution and place them in a small jar (like a baby food jar) and poke holes in the top large enough for ants to easily get in and out. Put the jar on top of the soil in your potted plants and the ants will be there shortly to take the bait. They will take pieces of the cotton ball back to the nest, where others will share it and be killed by its dehydrating effects.
An ant moat is an option if you want to prevent ants from getting into your plants to begin with. Small flowerpots may be set on a deep saucer and filled with water. Ants will not likely swim the moat to get to your plant. If they are already there, however, they will not be able to get out. So this is a preventive measure only.
Several home remedies exist to repel or kill ants in flowerpots. The use of baby powder sprinkled around the edges of the pot and on top of the soil will get ants moving out quickly as the smell and taste of the powder is highly offensive to them, according to GardenersWorldOnline.com. You may also use lemon tea tree oil (about 40 to 60 drops) mixed into a spray bottle of water to get rid of ants on plants. Spray this mixture directly on soil and leaves as it will not damage the plant, but it will drive ants away. Cinnamon and black pepper can be combined to create an unfriendly environment for ants in flowerpots. Sprinkle a half and half mixture of these spices on the dirt around your plant to repel ants and keep them away.