When a plant really needs a winter

A slow-down is one thing. True dormancy is another: some plants from cold-winter climates must have a cool rest each year to stay healthy.

The Venus flytrap is the classic example. It comes from the coastal Carolinas in the United States, where winters are chilly. The Carnivorous Plant FAQ advises a cool dormancy of about three months, chilly but not freezing, with continued sunlight and mix kept only barely moist. As autumn arrives, growth slows and leaves often blacken and die back over several weeks. That is normal, not a sign that the plant is dying. The United States Botanic Garden notes that dormancy needs vary between carnivorous plants: some require a distinct cool winter, others do not.

This matters when you buy a plant. If a plant needs a real winter, a constantly warm room cannot give it one without extra effort, such as a cool porch or balcony in a temperate climate. Before buying, check whether a plant needs dormancy, and whether you can provide it. Plants from the always-warm tropics, such as the tropical pitcher plants (Nepenthes) two lessons on, can be grown all year without one.