A sparingly water-soluble plant quality improver characterized by containing a polyvalent metal, an organic acid having a carboxylic group, an alkali metal and/or ammonia, and phosphate ions and/or carbonate ions. The sparingly water-soluble plant quality improver inhibits or alleviates physiological disorders of plants and further has the function of improving qualities of the plants, such as sugar content and acidity. It is also characterized in that it causes little fruit surface soiling to heighten the merchandice value, and that it is lowly phytotoxic and highly safe.
