Seedling culture in chemically active media presents challenges due to phytotoxicity associated with high contents of soluble salts. A greenhouse study was conducted to investigate the effect of direct leaching on the suitability of spent mushroom substrate (SMS) as a seedling nursery media. Germination, growth and nutrition characteristics of cucumber and hot pepper were compared among leached SMS (SMSL), unleached SMS (SMSU) and promix (PM) in a factorial design with three replicates. Seedling media significantly affected germination of hot pepper seeds, which was reduced to < 30% for the SMSU. Cucumber seeds showed > 90% germination across all media used. Across both crops, over the growing period, plants grown in SMSL showed consistently, and in most cases significantly (P< 0.05) greater heights and stem diameters than those in the SMSU and PM. Chlorophyll index (CI) was greatest for the unleached SMS and lowest for promix. At no time was there a significant difference in CI between the leached and unleached treatments. A similarly lower dry matter was shown for the unleached treatment compared to that of the others. Leached SMS resulted in either better or equal growth responses to PM, with the added advantage of not having to be fertilized.