Why don’t houseplants lose their leaves in fall?

Trees outside change color and go bare, but the plants on your windowsill stay green. Here’s why, and why winter can still make them drop leaves.

Every fall, the maples outside turn red and drop their leaves, while the pothos on the windowsill stays exactly the same. The short answer is that most houseplants come from places with no winter to prepare for, and your living room doesn’t have one either.

Why trees drop their leaves

As the days get shorter and the nights cooler, deciduous trees get ready to shed their leaves. A layer of cells forms where each leaf stem meets the twig, sealing it off until the leaf falls. Dropping leaves helps these trees save water and avoid snow and ice damage through the winter. The colors along the way come from pigments revealed and made as the leaf shuts down; see why leaves change color and when leaves fall for the whole story.

Dropping leaves is a response to climate, not something all plants do. Even within a species, whether a plant keeps its leaves year-round can depend on the climate it grows in (Encyclopaedia Britannica).

Most houseplants come from places without a winter

Many houseplants are native to tropical regions, where they’re used to plenty of warmth, humidity, and light (University of Wisconsin–Madison Extension). The weeping fig, for example, is a broadleaf evergreen from southeastern Asia and Australia (NC State Extension), and holiday cacti, though true cacti, come from rainforests (University of Minnesota Extension).

With no cold season to wait out, many of these plants grow as evergreens. Like pines and spruces, they don’t keep every leaf forever: older leaves wear out and are replaced a few at a time, rather than all at once in fall. See why evergreens don’t change color.

That’s the key: most tropical houseplants are naturally evergreen, so they don’t shed all their leaves at once in fall. Indoors, fairly steady temperatures and no frost help them keep their foliage all year, although changes in light and growing conditions can still make some leaves drop.

Winter is still hard on houseplants

Houseplants don’t have a fall, but they do notice winter, and that’s when many owners see leaves yellow and drop. Many tropical houseplants shed leaves and lose some of their color in winter (University of Wisconsin–Madison Extension). The usual causes:

• Low light. Light is the biggest limiting factor for many houseplants in winter (University of Wisconsin–Madison Extension). Move plants to a brighter window, or add a grow light. Supplemental lighting can make up for missing sunlight, and foliage houseplants do well with about 12 to 14 hours of light a day (University of Minnesota Extension). The right distance depends on the light, so follow its instructions.
• Dry air. Many tropical houseplants need humidity of at least 40 to 60 percent (University of Wisconsin–Madison Extension), and low humidity in winter often causes leaf and bud drop. Grouping plants, setting pots on a tray of wet pebbles (with the pots above the water), or running a humidifier helps (UConn Extension).
• Cold drafts. Drafts can make plants drop buds and leaves, so keep them away from outside doors and loose-fitting windows in the cold months (UConn Extension).
• Too much water and fertilizer. Plants need water less often during the cool, dim winter months (UConn Extension), and they need much less fertilizer when the days are shorter and growth slows (UConn Extension). Avoid overwatering in winter (University of Wisconsin–Madison Extension). Homes heated with wood stoves or forced hot air can still dry pots out quickly, so check the soil before watering (UConn Extension).

Leaf drop after a move

Some houseplants drop leaves simply because their surroundings changed. Weeping figs are famous for it: an abrupt change in light, especially from bright to dim, often triggers heavy leaf drop. Moving the plant in stages gives it time to adjust (Missouri Botanical Garden), and a moved fig usually drops leaves and then grows new ones (NC State Extension). That’s why a new plant brought home from a bright greenhouse may shed leaves in its first weeks.

Houseplants that do follow the seasons

Poinsettia. The closest thing to fall color indoors. Its bright red “flowers” are actually modified leaves called bracts, and they color up in response to shorter winter days. The true flowers are the tiny yellow ones in the center. Poinsettias are native to Mexico (University of Minnesota Extension). To get one to color again next year, it needs 16 hours of uninterrupted darkness each night, starting around September 21 and continuing until about Thanksgiving (University of Minnesota Extension). Night temperatures above 70 to 75°F can delay or prevent it (University of Illinois Extension).

Holiday cacti. Thanksgiving and Christmas cacti form flower buds as the days shorten, and they also need cool nights. At night temperatures around 55°F, they can bloom in five to six weeks, sometimes regardless of day length; at 60 to 65°F, they need about six weeks of nights at least 12 hours long. Above 65°F at night, they’re unlikely to bloom (University of Minnesota Extension).

Plants that rest. A few houseplants really do lose all their leaves. False shamrock (purple oxalis) often goes dormant, most often in summer after it flowers; its leaves turn pale, then brown, and fall off. Stop watering, keep it cool and dark, and new growth usually returns within one to three months (New York Botanical Garden). Elephant ears go dormant in cooler weather (University of Missouri Extension). Caladiums do the same: as nights cool in fall, their leaves fade and droop, and the tubers rest until spring. Gardeners in cold climates dig up outdoor caladiums and store the tubers indoors where it stays above 60°F (NC State Extension). A dormant plant usually slows down, yellows, and drops all its leaves, and needs less water and no fertilizer (University of Missouri Extension).

Normal or a problem?

• An occasional old, lower leaf yellows and drops: usually normal leaf replacement.
• Many leaves drop soon after a move or a new purchase: adjusting to new light; give it time and steady care.
• Leaves drop in winter near a window or door: check for drafts and low light.
• Brown, crispy leaf edges in a heated room: often dry air.
• Yellowing with soggy soil: often overwatering.
• A plant like oxalis or caladium drops everything: likely dormancy, not death.