7 Houseplants You Should Bring Inside in September – Before the Cool Nights and Pests Catch Them Out

A summer spent outdoors on a shaded patio or porch can be amazing for certain houseplants, most of which are tropical plants that thrive in heat and humidity. Soaking up the fresh air, natural moisture, warm breezes, and filtered sunlight can often trigger lush new growth. But in September, that outdoor haven can become a bit more risky. These tropical species like warm, consistent conditions, and sudden shifts in temperature can cause issues long before fall frost arrives.

Leaving these sensitive houseplants outside during sudden night-temperature dips can trigger rapid leaf drop, root rot, and severe cold shock. So this month is a time to transition key summering houseplants indoors to preserve all the vibrant momentum your plants gained over the summer. Sensible transitions now can protect against undue plant stress. This is also a good chance to get on top of any outdoor pests that might be looking to hitchhike indoors.

If you’re not careful, you could be bringing spider mites, scale, and mealybugs directly into your indoor spaces. By recognizing which tender species require a timely shift indoors, and taking a few quick steps to clean foliage and adjust soil moisture, you’ll protect your houseplant family and ensure they flourish through winter. Here are the key houseplants you need to move indoors now, and the easy ways to keep them clean and safe at the end of the summer holidays.

When the Houseplant Holiday is Over

There isn’t a single, universal date for bringing houseplants indoors for the winter. When you bring them in depends on your growing zone, local weather, exposure, and the types of plants you have. One of the best ways to determine when to make the transition is to keep an eye on nighttime temperatures. Many of your tropical houseplants will start to get uncomfortable when nighttime temps reach 50 degrees Fahrenheit (10 degrees Celsius) consistently. Some are even more sensitive to cold and should be brought in before the nights get this chilly.

The key to a successful fall houseplant migration is tracking nighttime minimums rather than daytime highs. While a sunny September afternoon might feel warm, a sharp drop to 50°F (10°C) at night triggers the plants' roots to enter survival mode. Extremely tender varieties will be susceptible the moment nighttime forecasts consistently touch 55-60°F (13-16°C). Delaying the transition leaves them vulnerable to chill damage, which manifests weeks later as black leaf margins, soft stems, or foliage collapse. If you’re not sure, the highly rated Serundo Digital Thermometer from Amazon can help you determine temperature and humidity levels outside.

Of course, indoor environments can present lower light levels, dry forced-air heating, and reduced airflow. To prevent severe acclimation shock, you need to ease your houseplants inside over a 7-10-day buffer window. For the best houseplant care at the end of summer, start by moving your designated potted travelers to a deeply shaded porch spot for a few days. This will help to get them used to lower light. You can then bring them indoors for the night, while leaving them out during warm days.

Before bringing any container past your threshold, you also need to perform a thorough pest inspection for each plant. Hose down foliage to dislodge hitchhikers, treat the soil with an organic neem drench, and inspect leaf undersides under high magnification so hitchhiking pests don't invade your home. To get a closer look under the leaves, use a loupe or pocket magnifier. The Jarlink 60X Illuminated Loupe Magnifier from Amazon is terrific value and gives crisp detail to flag up microscopic webs and crawlers before bringing pots indoors. Make this move as early in September as you can, focusing on these tender plants first…

1. Fiddle Leaf Fig

Fiddle leaf fig (Ficus lyrata) is a popular but tricky houseplant. It’s a tropical native and strongly dislikes both cold temperatures and sudden temperature changes. Summer outside can trigger a lot of new growth, but cold nights can lead to leaf drop due to stress. While a summer outdoors often pushes out large, glossy fiddle-shaped leaves, cold September drafts below 55°F (13°C) shock the root system. This stress causes the tree to jettison its lower foliage, leaving you with a sparse, leggy trunk.

This houseplant thrives in constant warmth and high humidity, so its return indoors is a high-stakes task. Move your fig inside early in the month (well before nighttime temperatures are consistently 50°F). Transition it into a spot that receives 6-8 hours of bright, indirect sunlight near an east or south-facing window, with no drafts or vents. Once indoors, give your fig a quarter-turn every few days, so all sides receive balanced light, preventing the trunk from leaning awkwardly toward the window.

Because indoor light is less intense than outdoor sun, soil dries out more slowly. Resist the urge to overwater: wait until the top 2-3 inches (8cm) of potting soil are dry to the touch before watering thoroughly. And remember to clean large leaf surfaces using Southside Neem Oil Houseplant Wipes from Amazon, which combine a layer of pest protection with impressive cleaning and instant sheen.

2. Bird of Paradise

Birds of paradise (Strelitzia spp.) are gorgeous flowering tropical plants that thrive in warm weather and can really put out a lot of new growth on a summer outdoor holiday. With their massive, banana-like leaves and bold silhouettes, they are built for high heat and brilliant sunlight. The right summer placement outside will allow them to stock up generous energy reserves for those distinctive blooms. But cool nights will slow that growth and stress the new foliage long before the first frost.

Bring your bird of paradise inside before the nights become cooler than 55°F (13°C) and place it in the brightest window you have to make the transition easier. Ideally, this needs to be directly in front of an unshaded south or west-facing window. The broad paddle leaves are likely coated in dust, hard water deposits, and spider mites. So give these leaves a good clean before moving day with a soft cloth and warm water or a diluted neem spray. For an extra treat, add a mild drench of Arber Organic Bio-Protectant Concentrate from Walmart to protect against fungal rots.

3. Rex Begonia

Begonia rex-cultorum hybrids, also known as Rex begonias, are gorgeous plants known for their striking foliage. Loved for their swirls of metallics, magentas, and rich emeralds, Rex begonias are among the most decorative yet cold-sensitive foliage plants. These pretty leaves are especially susceptible to cold damage, which can cause leaf margins to turn translucent, crisp, or drop off entirely. So bring yours indoors as temperatures start to drop to around 55°F (13°C).

Cool damp weather creates ideal conditions for powdery mildew to take hold on their textured surfaces, which is another great reason to bring these plants indoors. Place them in a spot indoors with bright but indirect light (not your sunniest window which can scorch their rich pigments). Allow the top inch of soil to dry between waterings and check moisture levels if you’re not sure. The Xlux Soil Moisture Meter from Amazon is a steal and works across every plant you own (just keep it clean).

4. Calathea

Calathea (classified under Goeppertia) is a group of plants prized for their multi-hued and striped leaves. Also known as prayer plants, zebra plants, and peacock plants, these striped beauties have a bit of a reputation as being divas, due to their precise environmental requirements. They require high humidity and steady warmth, and they don’t respond well to environmental changes. They are also vulnerable to nighttime temperatures that dip sharply to 60°F (16°C), which can cause leaf curling, crisp brown tips, and stem collapse.

Transition your calathea back inside over 7-10 days, once nighttime temperatures outside are 55-60°F (13-16°C). Choose a spot indoors that has bright but indirect light, far from drafts, vents or AC units. Tap water containing high chlorine or fluoride levels can cause leaf tips to turn brown, so hydrate with distilled or filtered water. Running a cool-mist humidifier can also ease the transition. For a budget humidity option, the Pure Enrichment MistAire Drop Ultrasonic Cool Mist Humidifier from Target is compact and great for small spaces.

5. Boston Fern

Boston fern (Nephrolepis exaltata) is a classic summer porch plant, with dense, frilly fronds. They make awesome summer porch staples, tumbling out of hanging baskets in feathery green cascades. However, their lush growth relies heavily on high summer humidity and steady airflow. As September brings cooler nights below 55°F (13°C), these ferns stop growing and prepare to shed fronds. Bringing them indoors before cool weather sets in will preserve their vibrant color, though you should prepare for some minor leaf shedding as they adapt to drier indoor air.

Bring these ferns inside before the nights are consistently cool. Be sure to check for pests before making the transition. Give the pot a firm shake, then spray with a gentle hose stream to wash away dust, whiteflies, and scale. Trim yellowed or bare fronds back to the crown. Then give yours a spot with bright, indirect light and good humidity: a large bathroom window or near a kitchen sink is ideal. For a light mineral boost that can help them adapt in peace, apply a diluted seaweed tonic such as Bloom City Organic Liquid Seaweed & Kelp Fertilizer from Walmart. A gentle soil soak strengthens delicate fern roots and improves frond retention indoors.

6. Tropical Hibiscus

Tropical hibiscus (Hibiscus rosa-sinensis) plants thrive outdoors in summer, blooming abundantly and putting out new green growth. With fiery, tropical blooms that draw hummingbirds all summer, it makes a dramatic outdoor patio centerpiece. But while some hibiscus plants are hardy, the tropical hibiscus cannot tolerate cold temperatures. Exposure to night temps below 55°F (13°C) can trigger leaf yellowing and bud drop. Bring your potted hibiscus indoors early in September, while night air is still mild, so it can settle before winter arrives.

Bring it indoors while temperatures are mild, about 60°F (16°C) at night. Your tropical hibiscus will fare best with a spot at your sunniest window. Where indoor light is limited, add an LED grow light for 10-12 hours daily. If you are going to invest in full spectrum lighting, get something that offers at least 35W, like the SANSI 35W Wall Mounted LED Plant Lights from Amazon to supply sun-hungry hibiscus trees with the light intensity they need. These plants can get large in summer, so give it a light trim, but avoid aggressive pruning during this stressful transition.

7. Anthurium

Anthurium plants (Anthurium spp.), also known as flamingo flowers, are loved for their glossy spathes and long-lasting reds and pinks. As a houseplant, they can bloom all year, and they really appreciate some time outdoors to soak up the warm, humid conditions. Outdoor summering encourages robust root systems and continuous flowering. However, when nighttime temperatures fall to 60°F (16°C), growth halts, leaves turn yellow, and emerging flower buds can abort. So you should bring yours indoors as soon as late-summer weather begins to turn cool.

Clean foliage surfaces with a damp cloth to dislodge hitchhiking scale insects or aphids before moving in. Then place your anthurium wherever it will receive bright, indirect light, such as near an east or curtained west-facing window. Avoid cold drafts and harsh afternoon sun that can scorch those glossy spathes. Allow the top 50% of the potting medium to dry out between waterings. Top-dress with a little epiphytic potting mix such as Miracle-Gro Coarse Potting Mix from Amazon.

Houseplant Cleaning Essentials

Transitioning your tropical houseplants indoors for autumn requires a few targeted plant care products and protective accessories. This collection of essential supplies will help you carry out your September plant move with total confidence, eliminating pests, supporting healthy roots, and keeping foliage lush and vibrant through the winter months ahead.

Timing is everything when transitioning sensitive tropical plants indoors, but success relies on patience and timing. Always ease your plants inside over several days, so they aren't shocked by sudden shifts in light and humidity. Before moving a single container past your threshold, perform a thorough pest inspection, wash off foliage, and treat the soil to protect your wider houseplant family.

Select indoor locations based on each plant's needs, placing sun-lovers near bright windows and delicate foliage species in humid, shaded spots. Remember, the earlier you begin the transition process, the easier it will be for your plants to settle in and maintain their lush beauty all winter long.

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