Ants & landscape plants
Ants are common throughout Colorado, and large numbers occur in the average landscape. Most ants are beneficial in controlling pest insects, destroying weed seeds and improving soil with their nesting habits. However, ants can cause problems when they nest in the lawn, garden or children's playground area.
Ant nests are produced underground, and colonies can contain thousands of workers. Carpenter ants are large black ants that usually construct their nests in decaying wood. Ants forage constantly during the summer months, and will chew through plant roots if their nest area is located adjacent to plants. Ants are highly adaptable in their nesting habits. You can usually find their nests by watching the movement of the ants. Although some ants build conspicuous mounds, others don't, so watching the pathway of the workers will direct you to the nest.
Ants that damage plants in the garden are sometimes associated with aphids that are feeding on the roots. Ants feed on the sweet excretion of the aphids, which protects the aphids and creates feeding tunnels in and around plant roots. Ants found climbing trees are either interested in the aphids feeding on the foliage, or the sap flowing from the tree as a result of natural causes, disease or injury. Ants are also attracted to peonies because of the sap the flower buds secrete. It's a myth that ants are necessary to permit peonies to bloom.
For more information, see the following Colorado State University Extension fact sheet(s).
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Updated Tuesday, November 19, 2013