To encourage spring and summer growth, fertilize every 6 weeks or so with a balanced houseplant fertilizer starting in late winter. Peace lilies are a tropical plant, so keep them in temperatures above 60°F (16°C) and away from cold, drafty windows. They do best in temperatures upwards of 70°F (21°C). The plant will droop a bit when thirsty, telling you when it needs a drink. If youpay attention to when it usually starts to sag, you can plan to water one day before it generally happens. Watering about once a week and spritzing leaves with water throughout the summer will help keep your peace lily hydrated.