Ants frequently make their homes in the soil of potted plants. While the ants themselves do not typically eat the plant tissue, their presence can be detrimental to the plant’s health. They build extensive tunnel systems that interfere with water absorption and disturb the plant’s root structure, leading to stress. If left unaddressed, an ant infestation can quickly grow, potentially spreading to other plants or migrating indoors into your home.
Why Ants are Drawn to Plant Soil
Ants are primarily attracted to plant containers for shelter and a reliable food source. The loose, well-aerated potting mix provides an ideal habitat for a colony, offering a protected location for the queen to lay eggs and for the larvae to develop. The soil’s consistent moisture level, especially near the drainage hole, makes the pot a suitable microclimate for their subterranean home.
The presence of honeydew-producing pests like aphids, scale, or mealybugs is a significant factor. These sap-sucking insects excrete a sugary, sticky substance called honeydew, which ants consume as a high-energy food source. The ants protect these pests from natural predators, allowing the pest population to explode and cause considerable damage to the plant. Finding ants should prompt an inspection for these secondary pests, as eliminating the ants often requires controlling their food source first.
Immediate Physical Removal Techniques
The first step is to physically remove the bulk of the colony from the soil. The most effective immediate treatment for a potted plant is the flushing or drowning method, which forces the colony to evacuate their underground tunnels. This process involves submerging the entire pot into a bucket of water, allowing the water level to rise above the soil line.
The water saturation forces the ants, including the queen and the brood, to flee the pot as their nest becomes flooded and anoxic. Adding a small amount of mild dish soap or insecticidal soap to the water helps break the surface tension and increases the drowning effect. The pot should be left submerged for 15 to 20 minutes to ensure the soil is fully saturated and the ants have been driven out.
If the infestation is severe or the flushing method proves insufficient, full repotting and soil replacement is necessary. Carefully remove the plant from its container and gently shake or rinse the infested soil away from the root ball, using a gentle stream of water to dislodge any remaining ants or eggs. Discard the contaminated soil immediately. Thoroughly clean the empty pot with a solution of water and mild soap before repotting the plant with fresh, sterile potting mix.
Targeted Natural Treatments for Infestation
Once the bulk of the colony has been removed, natural treatments can be applied to eliminate remaining ants and deter new ones. A highly effective and environmentally friendly substance is food-grade Diatomaceous Earth (DE), a fine powder composed of the fossilized remains of diatoms. This substance works mechanically, not chemically, by absorbing the protective waxy layer on an insect’s exoskeleton.
Sprinkle the dry DE liberally over the surface of the potting mix and around the base of the pot, creating a lethal barrier. The sharp edges of the diatom fossils cause microscopic abrasions that lead to dehydration and death for the ants. Note that DE loses its effectiveness when it becomes wet, so it must be reapplied after watering.
For a combined approach targeting both ants and their honeydew-producing food source, insecticidal soap or neem oil can be used as a soil drench. Dilute the product according to instructions and water the plant with the solution, allowing it to penetrate the soil where ant larvae and eggs may still reside. Neem oil, derived from the neem tree, is useful because it also disrupts the life cycle of pests like aphids and mealybugs, removing the ants’ primary motivation for nesting.
Certain aromatic substances can act as short-term deterrents due to the ants’ sensitive olfactory system. A light dusting of ground cinnamon on the soil surface or the application of a diluted peppermint essential oil spray can temporarily repel ants by masking their pheromone trails. These herbal deterrents can be used immediately after flushing or repotting to encourage remaining ants to leave the area.
Preventing Future Soil Invasion
A simple preventative measure is to physically block access points by sealing the drainage holes of the pot. Cut a piece of fine mesh screening, such as nylon window screen material, and place it over the drainage hole before adding soil to prevent ants from entering from below.
Elevating the potted plant off the ground is another physical barrier that limits access, especially for outdoor plants. Placing pots on metal stands, pot feet, or bricks creates a gap, reducing the ease with which ground-dwelling ants can climb into the container. Inspecting the immediate area for ant trails or nearby colonies can prevent an invasion before it starts.
Ants prefer dry soil for nesting because excessive moisture can drown their brood. Adjusting your watering routine to ensure the soil surface is consistently moist, but not waterlogged, makes the pot less attractive as a home. Regularly check neighboring plants for signs of aphids, scale, or mealybugs, and treat those pests promptly to eliminate the sugary honeydew, which is the most significant long-term attractant for ants.