Mulching with plastic or grass can affect soil temperature in a polyhouse. Plastic mulches, especially white, raised soil temperature more than grass mulch or no mulch. White plastic mulch had the highest soil temperature, followed by black plastic mulch. Grass mulch had the lowest soil temperature. Overall, all mulched and non-mulched treatments kept soil temperatures within the optimal range for growing warm-season vegetables. Plastic mulches are recommended for increasing soil temperature in cool seasons, while grass mulch can help lower soil temperature in hot seasons in polyhouse conditions.