Move These 7 Houseplants Inside in September

Seven specific tropical houseplants should be brought indoors in September to avoid damage from cool nights and pests, according to a guide from Gardening Know How. The publication states that sudden temperature drops can cause leaf drop, root rot, and cold shock long before the first fall frost.

A summer outdoors can trigger lush growth in tropical houseplants. But September's cooler nights pose a significant risk. The key to timing the move is monitoring nighttime temperatures, not daytime highs.

When to Make the Move

There is no universal date for bringing houseplants inside. The transition depends on your growing zone, local weather, and plant type. Many tropical houseplants become uncomfortable when nighttime temperatures consistently reach 50 degrees Fahrenheit (10 degrees Celsius). Some more sensitive varieties should be moved indoors before nights get that cool.

Extremely tender plants are at risk the moment nighttime forecasts consistently touch 55-60°F (13-16°C). Delay can lead to chill damage, which may manifest weeks later as black leaf margins or soft stems. To ease the acclimation shock from lower indoor light and drier air, the guide recommends a 7-10 day buffer period. Start by moving plants to a deeply shaded outdoor spot for a few days, then bring them indoors at night while leaving them out on warm days.

Preventing Pest Invasions

A thorough pest inspection is crucial before bringing any plant inside. The source warns that spider mites, scale, and mealybugs can hitchhike indoors. Foliage should be hosed down to dislodge pests, and the soil can be treated with an organic neem drench. Inspecting leaf undersides with a magnifier, like the Jarlink 60X Illuminated Loupe Magnifier from Amazon, is suggested to spot microscopic crawlers.

The guide focuses on seven tender plants that need priority attention for a September move indoors.

The Priority Houseplants

The source lists seven houseplants that require an early September move. Their cold sensitivity and key care tips for the transition are outlined below.

Fiddle Leaf Fig

Fiddle leaf fig (Ficus lyrata) strongly dislikes cold and sudden temperature changes. Cold September drafts below 55°F shock its root system, causing lower leaf drop. The guide advises moving it inside well before nighttime temperatures are consistently 50°F. Once indoors, rotate the plant a quarter-turn every few days for balanced light. Wait until the top 2-3 inches of soil are dry before watering.

Bird of Paradise

Birds of paradise (Strelitzia spp.) thrive in high heat and sunlight. Cool nights will slow growth and stress new foliage. Bring the plant inside before nights become cooler than 55°F. Its broad leaves are likely coated in dust and possibly spider mites, so they should be cleaned with a soft cloth and warm water before moving.

Rex Begonia

Rex begonias are highly decorative but cold-sensitive. Cool damp weather can cause leaf margins to turn translucent or crisp and encourages powdery mildew. They should be brought indoors as temperatures drop to around 55°F. Indoors, they need bright, indirect light, as direct sun can scorch their colorful leaves.

Calathea

Calatheas, also known as prayer plants, require high humidity and steady warmth. They are vulnerable to nighttime dips to 60°F, which can cause leaf curling and brown tips. Transition them back inside over 7-10 days once nights are 55-60°F. Use distilled or filtered water to avoid brown tips from tap water chemicals. A cool-mist humidifier can help.

The guide from Gardening Know How concludes by recommending this move be made as early in September as possible, focusing on these tender plants first.