Plants that live in temperate regions (places that experience warm summers, cold winters and moderate fall and spring temperatures) have to be able to survive during the cold winter months when temperatures often dip below freezing. Many plants go dormant during winter; dropping their leaves and halting all growth to protect them from frost. Tulips, maple trees, and roses for example all use dormancy to survive frost and the temperate carnivorous plants do the same!
What is Dormancy
A period of rest, when a plant isn’t actively growing but is still alive. Dormancy helps plants to survive during difficult times of year. In temperate regions most plants go dormant during winter to survive freezing temperatures. In warmer climates some plants go dormant during the hot and dry season to survive without water. Dormancy usually involves the leaves and sometimes stems of the plant dying back in fall and regrowing again in the spring when the temperatures rise again.
Dormancy in carnivorous plants
Venus Flytraps (Dionaea), America Pitcher Plants (Sarracenia), California Pitcher Plants (Darlingtonia), and some sundews (Drosera) and butterworts (Pinguicula) are temperate bog plants that both go dormant in the winter months to survive the cold temperatures. This means most if not all of their above ground foliage (leaves, traps and pitchers) will turn brown and die back in the fall and not return again until the spring. The rhizome of the American pitcher plant and California pitcher plant, and the bulb/stem of the flytrap remain alive but inactive under the ground during dormancy. Temperate sundews and butterworts often retreat into a hibernaculum, which is a dense coil of leaves that form a small nub. In the spring when temperatures warm up they will produce new foliage.
What to do during dormancy
Depending on where you live there are different steps that you need to take to make sure that your temperate carnivorous plants make it through their winter dormancy.
Temperate regions that only receive light frost
If your winter temperatures get cold but only rarely freeze, we recommend you keep your plants moist but not soaking wet and let them be outside to experience the cold to help push them into their dormancy. Temperate plants need to go dormant in order to thrive year after year. Once temperatures warm up in the spring and you notice the start of new growth you can go back to keeping your plants in their dish or tray of water to ensure they stay soaked during the warm spring and summer months.
Temperate regions that receive hard frost
If your winter temperatures regularly dip below 20 degrees F for extended periods of time we recommend that you keep your plants moist but not soaked and bring them into an unheated garage or basement window (or other chilly window) once temperatures get at or below 20 at night. Keep your plants in this cool but protected space throughout the winter. Only add small amounts of water if the soil is getting dry, Since the plant is not growing it will not be using the water. Most likely the soil will stay moist in a cool, protected area but winter air can be very dry so it is a good idea to check on them every couple of weeks to make sure they don’t dry out completely. Once spring arrives and the threat of frost is over bring the plants back outside to sit in water and full sun and they will produce new foliage.
We have read different accounts of people who have successfully grown temperate carnivorous plants in tropical regions using various methods to force dormancy. As we have never done this ourselves we do not have a method that we are confident in recommending.