Paper mill sludge (PMS), commercial peat and a commercial container medium (BYB No.4) were compared in the greenhouse for use as container media. Com posted PMS mixed with peat at ratio of 80% PMS (volume basis) supported plant growth, and relative leaf chlorophyll content of periwinkles comparable 0 commercial container medium (BVB No.4). Container medium amended with 50% composted PMS supported similar or better growth of ten different plant species than BYB No.4, except the root length of cosmos and chrysanthemum. Raw PMS supernatant inhibited seed germination of periwinkle. The inhibitory effect was eliminated when the raw PMS was well composted. Com posted PMS was compatible with the amended antagonistic microorganism and was good for production healthy periwinkle seedlings.