Ants live in colonies in soil, under logs and bricks, and in potted plants. While ants don't damage potted plants, having these insects nesting in or close to your house can lead to an infestation. Check for ants by lifting potted plants and looking underneath. Also keep an eye out for aphids, often a sign of an ant infestation. When you discover ants, you can either drown out the colony or replace the infested potting soil.
Small Potted Plants
To get rid of ants living in the potting soil of small container plants, use a bucket of water to drown them out. Select a bucket 2 to 3 inches wider than the pot and at least 1 inch deeper. Bigger is fine as long as the pot fits inside the bucket. Fill the bucket with room-temperature water, and add insecticidal soap. Use 2 tablespoons per 1/2 gallon of water. Set the plant in the bucket so that it is completely submerged, and let it soak for at least 20 minutes. After soaking, pull out the plant and set it outside or in the sink to drain. When using any type of insecticidal product, remember to wear gloves and keep children and pets from the treated area. Always read the product label for warnings about a particular product's toxicity.
Large Potted Plants
When ants move into large outdoor containers that are too big to submerge, you can still drown them out. Using pieces of plasticine, plug up each of the drainage holes. Fill the container with water and insecticidal soap, mixing 4 tablespoons to a gallon of water. Bring the water level right up to the lip of the container. Leave the pot plugged for 20 minutes, then pull out the plugs to drain the container.
An effective way to get rid of ants is to simply replace the potting soil. Start by turning the pot on its side and sliding the plant out of the container. Holding the plant by the root ball, brush off as much extra dirt as possible. Dispose of the ant-infested potting soil far away from the house and garden. Add fresh potting soil to the container and replant. Remember to water after repotting to settle the soil and reduce transplant shock.
Ants and Aphids
When aphids suck sap from your plants, they leave honeydew, a sticky sweet substance, on the leaves. Ants feed on the sweet excretion. You can discourage ants from colonizing the potting soil, particularly in outdoor potted plants, by keeping a close eye on aphid populations. Look for soft-bodied insects in groups on the leaves. These insects vary in color from yellow, green or brown to black. Check plants by looking under the leaves and along the stems. A magnifying glass can help to spot the tiny insects. Insecticidal soap is an effective way to destroy aphids. Dilute insecticidal soap using 1 teaspoon in a pint of water, then spray the areas of the plant affected by the aphids.