Many of us have mixed feelings toward a colony of ants. They can kill some plant pests that want to destroy our flowers and they can help aerate the soil around those flowers. They do, however, go after sections of leaves (to find food) and protect some insects like aphids that can do harm to our plants.
There are hundreds of species of ants, but one of the most common in the garden is the pavement ant. They don’t harm humans, but in each nest, there can be between three and ten thousand of them. It’s easy for these ants to become a problem as they move across the garden to collect food sources.
There are several things you can try to get rid of them. Some feel the fastest method is to pour boiling water into the entrance of one of their mounds. I need to warn you, however, that while this will kill the ants right away, the water can also kill plant roots that are also touching it.
You can use an environmentally safe insecticide, killing the ants it touches, but the remaining ants might just build a new tunnel to get to your plants, avoiding the area that the spray touched. Those sprays act as a barrier only and might be blown away in a strong wind and you will find yourself reapplying them often.
There are sticky traps, but these are more effective inside. You’d place them around the flower plant that is swarmed by a colony, and they will die trying to return to their nest.
Bait traps are more effective. The ants will bring the poison back to the colony and the hopefully the queen will be killed and soon the entire colony destroyed. You can make your own bait trap. Mix 2 tablespoons of honey, 2 tablespoons of peanut butter and 1/2 teaspoon of borax. Make up little bait motels that only ants can access (watch out that kids and pets don’t get ahold of them).
I want to mention that certain plants might deter ants from invading your garden. Plants with stronger scents like lavender or even cloves, rosemary or turmeric could help if planted around your garden.