Putting houseplants outside in summer can benefit many species, but it requires careful management of when, where, and how you do it. Most tropical houseplants appreciate the higher humidity, fresh air, and natural light of a sheltered outdoor position in summer. However, they are susceptible to direct harsh sun, sudden cold nights, heavy rain, and pests they would not encounter indoors. Done correctly, a summer outdoors helps many plants grow vigorously; done carelessly, it can damage or kill them.
Which Houseplants Benefit from Going Outside
Tropical foliage plants that have been growing in typical indoor light conditions benefit most from the increased light intensity and humidity of an outdoor summer. Monsteras, Philodendrons, Pothos, Calatheas, Peace Lilies, and most aroids respond well to a sheltered outdoor position with bright indirect light or dappled shade. Growth often accelerates noticeably when these plants are moved outside in summer, producing larger, more robust leaves than they would indoors.
Cacti and succulents thrive outside in a sunny position, provided rain is not excessive and they are not left in waterlogged conditions. Some succulents and cacti actually benefit from a Mediterranean-style summer outdoors: maximum light, warmth, and allowed to dry out between waterings. Many orchids also benefit from a summer outdoors in a sheltered, shaded position with good air circulation.
When to Move Plants Outside
Do not move tropical houseplants outside until night temperatures are reliably above 12 to 15 degrees Celsius. In the UK, this typically means waiting until late May or early June, depending on the year and region. Even a single cold night below 10 degrees can cause cold damage to sensitive tropical plants, producing brown patches on leaves, blackening of stems, and in severe cases, fatal damage to growing tips. Check the forecast before moving plants out and be prepared to bring them back in if a cold night is predicted.
At the end of summer, move plants back indoors before night temperatures drop below 12 degrees, typically from early September onward. Do not leave tropical plants outdoors into autumn, hoping for one more warm spell... A single cold night can undo the benefits of the whole summer.
Acclimatisation is Key
Plants grown indoors are adapted to lower light levels. Moving them directly into bright outdoor sun causes scorch, even on plants that are described as sun-lovers. The same plant that would eventually tolerate full sun needs two to three weeks of gradual acclimatisation before being placed in direct outdoor sun. Start in full shade outdoors, move to dappled light after a week, then to more light gradually. This gives the plant time to produce leaves adapted to higher light intensities.
Even after acclimatisation, most tropical foliage plants prefer bright outdoor shade (under a tree canopy, on a shaded patio) rather than full direct sun. Direct south-facing outdoor sun in June and July is far more intense than any UK windowsill and will scorch most tropical plants. See our guide on too much light for more detail.
Pest Risk When Going Outside
One significant downside of putting houseplants outside is the increased exposure to outdoor pests. Vine weevils, slugs, aphids, and scale insects can colonise plants left outdoors, and you will bring them back inside in autumn. Before returning plants indoors, inspect them thoroughly, check under every leaf and in every leaf axil, and consider a preventive treatment with insecticidal soap or neem oil. Repotting at this point, or at least removing the top layer of compost and replacing it with fresh, reduces the risk of introducing vine weevil larvae or other soil-dwelling pests.
Learn more about pests and how to manage them here.
Rain, Drainage, and Waterlogging
UK summers can include significant rainfall. Ensure all pots have drainage holes and that they are not sitting in saucers that fill with rainwater. Plants in pots without drainage holes can become severely waterlogged during heavy rain. Position plants where they receive shelter from very heavy rain if possible, particularly cacti and succulents, which do not tolerate prolonged wet conditions. The natural increase in watering from rainfall means you will need to water less frequently while plants are outside.