A summer outside can do a houseplant a lot of good. Iowa State Extension says the warmth, humidity, extra light and fresh air let plants put on lots of new, healthy growth. Clemson HGIC says most houseplants benefit, except those with fuzzy leaves such as African violets.
The risks are predictable: cold nights, sunburn, wind, waterlogged pots and pests that ride back indoors. Each has a simple check.
Night temperatures: when it is safe to go out and time to come in
The sources agree on the direction but use different thresholds. Clemson and NC State are more cautious than Iowa State.
| Source | Move outdoors when | Bring indoors when |
|---|---|---|
| Iowa State Extension | Nights consistently and reliably above 10 °C (50 °F) | Nights dip consistently to around 10 °C (50 °F) |
| Clemson HGIC 1454 | After frost; to be safe, nights consistently above 16 °C (60 °F) | Outside and inside temperatures are about the same, before the heating goes on |
| NC State Extension | Nights consistently above 16 °C (60 °F) | Before nights drop below 16 °C (60 °F) |
| University of Maryland Extension | — | Protect plants from temperatures below 10 °C (50 °F) |
Iowa State says several species are damaged below about 7 °C (45 °F), and nearly all die below freezing. Clemson says 10 °C (50 °F) or lower can damage many tropical plants. Watch the forecast and bring plants in early if a cold night is coming.
Before the move: repot and stabilise
Iowa State suggests sorting plants a few weeks before the move. Repot any that need it, because the extra growth outdoors makes pot-bound plants dry out fast or tip over. Go up only one or two pot sizes.
For wind, Iowa State recommends broad, wide-based pots or heavy materials such as ceramic. Spring is also a good time to trim lanky stems, since plants recover quickly outdoors.
Hardening off to sun
Indoor leaves are not ready for outdoor light. Iowa State says even the brightest indoor spot gets only a fraction of the light in any shady spot outside. Nearly all houseplants are tropical understorey plants.
Iowa State’s rule is blunt: never move houseplants from indoors into full sun. Leaf burn, discolouration and drop can follow. On succulents, the damage to fleshy stems and leaves is permanent.
| Source | Hardening-off method |
|---|---|
| Iowa State | Full shade outdoors first, then more light over 10–14 days. Use shade cloth if you have no fully shaded spot |
| Illinois Extension | No direct sun. A few hours outdoors on day one, more each day; ready after 1–2 weeks |
| Clemson HGIC 1454 | A few days in deep shade under a tree, then gradually brighter |
| Maryland Extension | Start with 2 hours of full sun a day and gradually lengthen it |
Where plants end up depends on the plant. Iowa State says many houseplants can stay in full shade all summer. Clemson places foliage plants in heavy to light shade, while most succulents and cacti tolerate full sun.
Watch closely for the first few weeks. Iowa State says burning or discolouration means the light is too intense. Leaning or stretching means the spot is too dark. Weeping fig and tropical hibiscus may drop leaves even after a gentle move, and new leaves replace them.
For plant-specific damage, see our sunburn guides for pothos, spider plant and indoor citrus.
Wind, rain and drainage
Clemson HGIC suggests a spot out of drying winds where the plants will still get rain. NC State says to protect moved plants from cold winds. The RHS notes that high winds damage the upper and windward sides of plants and dry leaves out, causing browning and loss of leaves.
Rain helps. Iowa State says summer rain cleans dust off the foliage. It does change drainage needs:
- Set pots on pot feet or bricks so the drainage holes stay clear (Clemson).
- Do not stand pots in saucers outdoors. Clemson warns a saucer can hold too much water and cause root rot.
- Watch leaves during wet spells. Clemson HGIC says bacterial leaf spots enlarge and run together in wet conditions, such as plants put outside in rainy periods.
Watering and feeding outside
Plants grow faster outdoors and use more water and fertilizer, according to Clemson. In the heat of summer it may be necessary to water daily when rain is not enough.
Iowa State says to check soil moisture often and water thoroughly when the mix is dry to the touch. Grouping plants near a hose makes this easier. For feeding, it suggests a balanced, water-soluble fertilizer at half strength every week or every other week. A slow-release fertilizer at the start of the season works too.
Our fertilizer schedule covers how to taper feeding once plants come back in.
Bringing plants back in: pests first
Pests are the main risk of the return trip. Iowa State lists scale, mealybugs, aphids and whiteflies on foliage, and ants or cockroaches in the soil. Maryland adds caterpillars, beetles, slugs, earwigs, sowbugs and millipedes.
- Inspect foliage, stems and the mix. Clemson suggests sliding plants out of their pots to check for anything that has crawled in through the drainage holes.
- Rinse all foliage with a hose while still outside, then let it dry (Iowa State).
- Treat if needed. Clemson sprays leaves, mix and pot with insecticidal soap, reapplies after several days, then brings plants in 2–3 days later. Check the label for your plant, or test a small area first: Clemson says symptoms can take 7–10 days to appear.
- Repot if the mix is infested. Maryland recommends fresh potting mix for insects in the mix. Illinois suggests repotting into fresh mix before plants return indoors.
- Isolate. Iowa State keeps returning plants away from others for 3–4 weeks; Illinois says 2–3 weeks. Pests usually show within a month.
Iowa State adds a hard truth: if a plant is heavily infested, composting it may be better than infesting the rest of your collection.
For identification and treatment, see our houseplant pests guide.
Re-acclimating to indoor light
The return is a drop in light, and plants react to that too.
- Step down gradually. Clemson moves plants from sun to light shade to heavy shade and then indoors over about a week. NC State suggests the brightest, most humid indoor spot first, then a gradual move to the winter location over four to eight weeks.
- Pick bright, indirect light. Iowa State says hibiscus and weeping fig often drop leaves after the move. New leaves will replace them. Clemson says some yellowing or leaf drop is normal as plants adjust.
- Do not prune hard. Iowa State warns that drastic pruning adds stress. Trim only what is needed to fit the plant indoors.
- Change care. Iowa State says to reduce or stop feeding in autumn and winter. Watering needs change because light, humidity and temperature all change.
Our houseplant care calendar puts both moves in a seasonal plan.
References
- Iowa State University Extension and Outreach: Moving Indoor Plants Outside for the Summer
- Iowa State University Extension and Outreach: How and when do I bring my houseplants back indoors before winter?
- Clemson Cooperative Extension HGIC 1454: Moving Houseplants Indoors & Outdoors
- Clemson Cooperative Extension HGIC 2251: Houseplant Diseases & Disorders
- NC State Extension: Extension Gardener Handbook, Chapter 18: Plants Grown in Containers
- University of Illinois Extension: Houseplants: Care
- University of Maryland Extension: Excess Light on Indoor Plants
- University of Maryland Extension: Diagnose Indoor Plant Problems
- Royal Horticultural Society: Weather damage