Mexican or Tropical Butterworts are great for a sunny windowsill. When grown under high intensity fluorescent grow lights many of them will blush so that the entire plant is glowing pink or red! Warm Temperate Butterworts do well outdoors in part sun to full sun with a bit of protection from afternoon sun. More information about light is available here (Link).
All temperate and warm temperate species should be grown permanently wet on the tray system, with frequent overhead watering. Use chilly water for your temperate pings. The Mexican varieties can be kept on the tray system with overhead watering while they have carnivorous foliage in summer and autumn. When the rosettes change to their small succulents in winter, keep the soil on the dry side, dampening them only occasionally. Cuban species should be kept wet year-round, with only slight winter drying. Only use rain, distilled or reverse osmosis water free of minerals. More information on what water to use is here (Link).
Temperature and Dormancy:
Butterworts grow across the globe and come from varied climates. Temperate Pinguicula need cold winters while they are dormant to thrive. The warm temperate species from the U.S. tolerate light frost and brief freezes. They do best outdoors in areas with mild winters. Mexican Butterworts do well in terrariums, greenhouses and windowsills with appropriate water and lighting.
Mexican or Tropical butterworts have a winter dormancy that is marked by a change in the leaves from their carnivorous type to a tighter, more succulent leaf. When the Pinguicula has formed these tight, succulent leaves you can withhold water as described above for the dormancy period. Make sure to wait for the butterworts to go dormant before you stop watering. And when they begin growing their carnivorous leaves again in the spring you should begin the tray method of watering again. Do not worry too much about providing this dormancy; if your plants do not start to grow the succulent type leaves, which look very different than their regular leaves, you do not need to withhold water.
Information on soil types can be found on my soil page (Link).
Fertilizing and Feeding:
Temperate species grown outdoors will catch their own food. You use Schultz cactus fertilizer (Link on Amazon) on Mexican and Tropical Pinguicula, applying to the leaves only and following the instructions on the packaging for dilution. More information about fertilizer can be viewed here (Link).