Methods for applying a treatment, such as colorant, to an installed landscaping material (such as wood chips or mulch), reducing the need to replace worn or weathered material. The methods include applying a pre-treatment to protect elements proximate the landscape material that are not to be treated, applying a treatment liquid to the landscaping material by spraying, and then rinsing any elements proximate the landscape material that may have be inadvertently and undesirably treated. Also described is a sprayer apparatus for applying treatment liquid to a landscaping material. The sprayer apparatus includes first and second spray outlets and an agitator therebetween. In use, the landscape material to be treated is first sprayed, the material is agitated (e.g., turned), and a second spray of treatment liquid is applied to the landscape material.