Identium
Bringing Plants Indoors for Winter: Do This Before the First Frost
The plant that loved your patio all summer is about to lose half its leaves. Some of that is unavoidable. Most of it is not.
If you put houseplants outside for the summer, this is the two weeks that decide how they look in February. Get it wrong and you import spider mites into a warm house, or shock a plant so hard it drops everything it grew since May.
None of it is difficult. It is just a sequence, and most people skip straight to the last step.
When to do it
Start when night temperatures drop to around 10 to 13°C, or 50 to 55°F. Not when frost is forecast. By then you are rushing.
Most tropical houseplants start suffering well above freezing. Cold damage on a monstera or a philodendron can begin in the low 40s Fahrenheit, and it shows up as blackened patches days later, long after you have brought it in and assumed it was fine.
Watch the ten day forecast from early September. When the overnight lows start touching 13°C, begin the process. Give yourself two weeks, not two hours.
Cold damage is not a frost event. It starts in the low 40s Fahrenheit and shows up as black patches a week later.
Rule of thumbStep one: debug them, properly
This is the step people skip, and it is the one that matters most. A plant that has spent four months outdoors is carrying passengers, and a warm house with no predators is paradise for all of them.
- Inspect leaf undersides, stem joints and the growing tip on every plant. Use a torch. Look for webbing, white fluff, brown bumps, and anything that moves.Look first
- Hose the whole plant down, top and underside of every leaf. Physical removal does more than any spray.Rinse
- Check the pot itself. Slugs, woodlice, earwigs and ants shelter under the rim and in the drainage holes. Tip the pot and look.Under the rim
- Submerge the pot in a bucket of water for 15 to 20 minutes. Anything living in the soil comes to the surface. Let it drain fully afterwards.Soil soak
- Treat with insecticidal soap or neem, covering leaf undersides, whether or not you saw anything.Treat anyway
- Quarantine for two weeks away from your existing houseplants, checking twice a week.Quarantine
Two weeks of quarantine feels excessive until the year you skip it and spend February fighting spider mites across fifteen plants.
Step two: acclimatise gradually
Outdoor shade is still far brighter than the brightest windowsill. Moving a plant straight from a patio to a living room is a light drop of maybe ninety percent, and the plant responds by shedding the leaves it can no longer support.
Over a week to ten days, move it in stages. Full sun to bright shade for a few days, then deep shade or a covered porch, then indoors. Each step lets it adjust rather than panic.
Do the same thing in reverse next spring, or you will sunburn everything in a day.
Step three: repot only if you must
Plants grow fast outdoors and many will be pot bound. It is tempting to repot everything before bringing it in.
Resist, mostly. Repotting is another shock on top of the light change, and the plant is heading into the season where it grows least and recovers slowest. Unless roots are bursting out of the pot or you find rot, wait until spring.
Do knock off the top layer of soil and replace it with fresh mix if the surface is full of debris, moss or insect eggs.
What to expect once they are in
Leaf drop. This is normal and it is not a failure. Expect to lose some of the oldest leaves as the plant sheds what the reduced light will not support. A fiddle leaf fig may drop a lot. A monstera drops a few. It is adjusting, not dying.
What is not normal: rapid loss of many leaves at once, mushy stems, or wilting while the soil is damp. That is cold damage, overwatering, or both.
Cut watering roughly in half immediately. This is where most plants actually die. A pot that dried out in three days on a windy patio can take three weeks on a windowsill in November. Keeping the outdoor watering rhythm indoors drowns them.
Stop feeding until spring growth resumes.
Keep them off radiators and out of draughts. A plant that just came in from outside is already stressed, and a hot dry updraft from a radiator is the fastest way to crisp it.
The plants that need extra thought
Tender perennials you want to keep. Geraniums, fuchsias, begonias. These can be overwintered in a cool bright spot, watered sparingly, and cut back by about a third. They are not trying to grow, just survive.
Tropical bulbs and tubers. Dahlias, cannas, caladiums. Lift after the first frost blackens the foliage, dry them off, and store the tubers somewhere frost free and dark rather than keeping them in leaf.
Citrus. Wants the coolest bright spot you have, ideally 10 to 15°C. In a warm living room they drop leaves and attract scale.
Cacti and succulents. Want a cool dry rest. Water very little from now until spring. Many need that cool dry period to flower next year.
Two weeks of work for the whole winter
The plants that die in January are almost always the ones that came in during a panic on the night of the first frost warning, unwashed, straight from full sun into a dark corner, and then got watered weekly out of habit.
If you are not sure what a particular plant needs over winter, or you inherited something and never knew what it was, photograph a leaf with the stem visible. Identium will name it and tell you whether it wants a cool dry rest or a warm bright windowsill, which is a bigger difference than it sounds.
Frequently asked questions
When should I bring my plants inside for winter?
When night temperatures start dropping to around 10 to 13°C or 50 to 55°F, not when frost is forecast. Most tropical houseplants begin suffering cold damage in the low 40s Fahrenheit, and the damage often only becomes visible as black patches a week later. Give yourself about two weeks for the whole process.
How do I stop bringing pests indoors with my plants?
Inspect leaf undersides and stem joints with a torch, hose the whole plant down including undersides, check under the pot rim and in the drainage holes, submerge the pot in water for 15 to 20 minutes to flush soil dwellers, treat with insecticidal soap or neem whether or not you saw anything, then quarantine for two weeks.
Why is my plant dropping leaves after coming indoors?
Because outdoor shade is far brighter than any indoor spot, so the plant sheds leaves it can no longer support. Losing some older leaves is normal. Moving plants indoors gradually over a week to ten days reduces it considerably. Rapid loss of many leaves, mushy stems or wilting in damp soil is something else and usually means cold damage or overwatering.
Should I repot before bringing plants inside?
Usually not. Repotting adds a second shock on top of the light change, going into the season when plants grow least and recover slowest. Wait until spring unless roots are bursting from the pot or you find rot. Replacing the top layer of soil is fine and worth doing if the surface is full of debris.
How often should I water plants once they come indoors?
Roughly half as often as you did outdoors, and check the soil rather than following a schedule. A pot that dried out in three days on a windy patio can take three weeks on a windowsill in November. Continuing the outdoor watering rhythm indoors is the most common way these plants die.