The practice of bringing outdoor container plants inside for the colder months is known as overwintering. This strategy focuses purely on survival, allowing species sensitive to freezing temperatures to bypass the harsh winter environment and remain viable for the next growing season. This process saves tropicals, herbs, and tender perennials that would otherwise perish when temperatures drop consistently below 50 degrees Fahrenheit. The goal is to sustain the plant in a state of semi-dormancy until spring returns, not to encourage vigorous growth or flowering.
Identifying Outdoor Plants Suitable for Indoor Transition
Successful candidates for overwintering are non-hardy plants that do not require deep, cold dormancy. Tender tropical plants, often grown as annuals, transition well into temporary houseplants, such as tropical hibiscus, mandevilla, and container-grown citrus trees. Succulents and cacti also make excellent indoor guests because their native environments rarely experience frost; their fleshy leaves make them highly susceptible to damage from freezing. Potted herbs, particularly woody perennials like rosemary and bay laurel, can be brought inside, as can Pelargoniums (geraniums), which often continue to bloom with sufficient light.
Essential Steps for Pre-Move Preparation
The transition indoors must be preceded by a meticulous cleaning process to avoid introducing pests and disease into your home. Thoroughly inspect the foliage, stems, and the underside of leaves for signs of common pests like aphids, spider mites, or whiteflies. Pruning is also necessary to reduce the plant’s size and remove any dead or heavily infested material before entry.
A crucial step involves treating the plant to eliminate any unseen insects lurking in the soil or on the surface. Drenching the soil with an insecticidal soap or a diluted neem oil solution helps eradicate pests; soak the soil a few hours before the move to ensure thorough saturation. Once inside, place newly arrived plants in a quarantine area separate from existing houseplants for two to three weeks to monitor for delayed pest outbreaks.
Adjusting Care Requirements for the Indoor Environment
Once plants are moved inside, their care regimen must be altered to reflect the reduced light and warmth of the indoor setting. The intensity of natural sunlight near a window is significantly lower than outdoor exposure, especially during the shorter winter days. Plants that were in full sun outside should be placed directly in the brightest south-facing window possible, or supplemented with a dedicated grow light to prevent etiolation, or “stretching.”
Watering frequency needs to be substantially reduced, as the plant’s metabolic rate slows down in lower light. Most overwintering plants should only be watered when the top inch or two of soil is completely dry to the touch, preventing root rot. Fertilizer application should be entirely suspended until new growth resumes in the spring, as feeding a dormant plant can lead to salt buildup that burns the roots. Since indoor heating dries the air, grouping plants together or placing them on a humidity tray filled with pebbles and water can help raise the surrounding moisture levels.
Outdoor Plants That Must Remain Outside
Not all outdoor plants benefit from being moved indoors, particularly those that require a period of cold temperatures to complete their natural life cycle. Many common perennials and flowering shrubs, such as lilacs and peonies, need a specific number of chilling hours to set buds for the following season. Denying this required deep dormancy by bringing them into a warm house will prevent them from flowering or thriving when they are returned outside. True annuals, like marigolds or zinnias, are programmed to complete their life cycle in one season and are generally not worth the effort of overwintering. Furthermore, large, mature plants or those deeply rooted in the ground are impractical to move, as attempting to dig up and pot a large garden specimen often causes irreparable root damage.