Houseplants that spend the summer outdoors come back sturdier, but the return trip has predictable problems. Insects hitch a ride in the foliage and the soil. The sudden drop in light makes leaves yellow and fall. And a plant that was drinking hard in July gets watered at the same pace in a dim October living room.

None of this is hard to prevent. It comes down to timing, a careful look at every pot, and a few weeks of adjusted care.

The short answer

  1. Move them when nights start dipping into the 50s °F, and well before the first frost. Most houseplants are damaged in the mid-to-low 40s.
  2. Inspect every plant before it comes in: leaf undersides, stems, the soil surface, and the pot's drainage hole. Rinse the foliage outdoors and let it dry.
  3. Keep new arrivals apart from your other houseplants for three to four weeks, while any hidden pests show themselves.
  4. Ease the light change over about a week, then give them your brightest windows. Expect some leaf drop anyway.
  5. Water and feed less. Plants grow slowly indoors in winter, so they use less of both.

When to move them

Watch the overnight forecast rather than the calendar. Iowa State Extension advises moving houseplants back indoors once nighttime temperatures dip consistently into the 50s °F. In Iowa, that is typically mid-to-late September; farther south it comes later. Many tropical houseplants are damaged by temperatures in the mid-to-low 40s, and nearly all die if exposed to freezing.

Don't wait for a frost warning. By the time frost is forecast, plants have usually spent several nights in the chilling range. Moving them while nights are still in the 50s also gives you daylight hours to do the inspection properly, rather than hauling pots inside in the dark before a cold snap.

If a sudden cold night comes before you are ready, bring the plants into a garage or porch for the night. Then do the inspection the next day before they join your other houseplants.

Check for pests before they come in

Outdoors, predators and weather keep most pests in check. Indoors there are no predators, and the warm, still air suits sap-feeders and mites, so a few insects in September can be a full infestation by January. This is the step that matters most.

Take each plant into good light and look at:

  • Leaf undersides and stems, especially where leaves join the stem. Look for aphids, the waxy tufts of mealybugs, the immobile bumps of scale, whiteflies that rise when you brush the plant, and the fine stippling and webbing of spider mites.
  • The soil surface and the pot's drainage hole. Ants, slugs, earwigs, and other soil insects often move into pots that sat on the ground all summer. If you can, slide the plant out of its pot and look at the root ball.
  • Sticky leaves or black sooty residue, which point to sap-feeding insects even when you cannot see them.

Then rinse the foliage thoroughly while the plant is still outdoors, top and underside, and let it dry completely before bringing it in. A strong spray of water removes a surprising share of aphids, mites, and whiteflies.

If you find an established problem, deal with it outdoors. Prune out heavily infested stems, and if a treatment is needed, use an insecticidal soap or horticultural oil labeled for houseplants. Coverage of the leaf undersides is the whole job with both. The pest identification guide covers the options in order.

Keep them apart for three to four weeks

Even a careful inspection misses eggs and the smallest insects. Iowa State Extension recommends keeping plants that have been outdoors isolated from your other houseplants for three to four weeks. If pests such as scale, mealybugs, aphids, or whiteflies are going to appear, they usually show up within a month.

A spare room, a separate windowsill, or a table on the far side of the room is enough. Check leaf undersides once a week during that time. When the month is up and the plants are clean, they can join the rest of your collection.

Ease the drop in light

Light outdoors, even in shade, is far brighter than light inside a house. A plant that moves straight from a sunny patio to a living-room corner is being asked to live on a fraction of the light it just had. It responds by shedding the leaves it can no longer support.

You can soften the change:

  • Acclimate gradually. Over about a week before the move, shift plants into progressively shadier spots outdoors, such as under a tree or on the north side of the house.
  • Give them your best light indoors. South- and west-facing windows are usually the brightest. The houseplant light guide explains how far light falls off with distance from the glass.
  • Add a grow light for plants that need more than your windows can give.

Some yellowing and leaf drop in the first few weeks is normal, and it slows once the plant adjusts. The yellow leaves guide explains how to tell this adjustment from a real problem.

Water and feed less

Indoors in winter, with lower light and cooler temperatures, houseplants grow much more slowly than they did outside, and they use far less water. Overwatering is the most common way plants are lost after the move.

  • Water by feel, not by habit. Check the potting mix with your finger and water when the top has dried, rather than on the summer schedule. Let excess water drain away, and don't leave pots standing in full saucers.
  • Cut back on fertilizer. Iowa State Extension recommends reducing or stopping fertilizer through fall and winter; feeding a plant that isn't growing only pushes weak growth it cannot support. Resume in spring when new growth starts.
  • Leave repotting for spring where you can, unless a plant is badly root-bound or its mix stays waterlogged. A plant adjusting to less light grows too slowly to fill new mix quickly.

Dry air, heat, and drafts

Most houseplants come from humid tropical climates. Heated indoor air in winter can be much drier than anything they experienced outdoors, with relative humidity sometimes as low as 10 to 20 percent. Dry air shows up as brown leaf tips and edges, and it favors spider mites.

  • Keep plants away from heat vents, radiators, and fireplaces, and from doors that let in cold drafts. Weeping figs in particular drop leaves heavily when set near a heat vent or draft.
  • Group plants together, which raises humidity slightly around them, or run a humidifier in the room.
  • Mind cold glass. Leaves pressed against a window on a freezing night can be injured. Pull plants back a few inches on the coldest nights.

Plants that need something different

Citrus. Lemons, limes, and other potted citrus need as much light as you can give them indoors, ideally a sunny south window. Iowa State Extension advises bringing them in before nights drop into the 40s.

Tropical hibiscus. Expect it to drop leaves and stop growing while it adjusts. Give it bright light near a south or southwest window, cut back on water, and don't fertilize until you see new growth. It may flower again indoors once it settles.

Tender bulbs and perennials. Cannas, dahlias, gladiolus, caladiums, and similar plants grown from bulbs, corms, or tubers are usually stored dormant rather than grown as houseplants. The November guide covers digging and storing them.

Frost-tender plants you are leaving outside. For containers too large to move and garden plants you want to carry a little further into autumn, see how to protect plants from frost.

A move-in checklist

  1. Check the ten-day forecast. Plan the move for the first run of nights in the 50s °F.
  2. A week ahead, shift plants into shadier spots outdoors.
  3. On moving day, inspect leaves, stems, soil, and drainage holes. Slide out root balls where you can.
  4. Rinse the foliage, top and underside, and let it dry.
  5. Treat any pests you find before the plant comes inside.
  6. Clean the outside of each pot and saucer.
  7. Place the plants in bright light, away from your other houseplants.
  8. Water only when the mix has dried at the top. Skip fertilizer until spring.
  9. Check leaf undersides weekly for a month, then let the plants join the rest of your collection.

Sources and further reading