One of the potential uses of processed cotton gin by-products (gin waste or gin trash) is as a mulch in bedding plant applications. A value-added technique known as the COBY Process was used to produce three mulches from different types of gin waste (Arizona picker trash, ground Texas stripper trash, and Texas stripper trash). This study compared the effectiveness of the COBY products with the raw material from which they were produced and with a conventional wood mulch on weed suppression. Mulches were applied at 1.47, 2.94, and 4.39 kg/m2. The COBY mulches performed equal to or better than the raw gin waste or the wood mulch in suppressing weeds; however, ageratums planted in two of the COBY treatments exhibited signs of reduced plant growth. The reduced plant growth appeared to be due to high soluble salt concentrations. The increase in soluble salts of the COBY product could be attributed to the water and dye solutions used in the processing. The COBY process can be used to produce a mulch that is effective at suppressing weed growth. The process needs refinement to minimize any negative characteristics or properties for COBY mulch applications where salt sensitive bedding plants are being grown.