Preferred Temperature: 60º - 75º
Spearmint grows best in indoor temperatures that mimic its natural habitat. When growing spearmint indoors, the ideal temperature range is between 65°F (18°C) and 75°F (24°C) during the day and about 60°F (15°C) at night. Extreme temperature changes should be avoided, and the plant should not be exposed to drafts, direct cold, or direct heat sources. Spearmint can survive a little bit cooler temperatures, especially in the winter, but it should be covered from below-freezing temperatures because it is vulnerable to frost. Your indoor spearmint plant will grow healthily, produce foliage, and develop flavor if you maintain a consistent, moderate temperature throughout the year.