Orchids belong to the vast and diverse plant family Orchidaceae, containing tens of thousands of species that span nearly every continent. Whether these plants belong indoors or outdoors depends entirely on the specific species and the local climate where they are grown. Most commercially available orchids are tropical hybrids requiring stable, warm conditions year-round, making an indoor environment the most suitable choice for the average grower. Cultivating these plants requires replicating the gentle, consistent conditions of their native jungle habitats within a controlled space.
Why Most Orchids Thrive Indoors
Most commercially purchased orchids, such as Phalaenopsis (Moth Orchid), Cattleya, and Dendrobium species, originate from tropical or subtropical environments. In their native habitats, these orchids often grow as epiphytes, meaning they cling to trees rather than growing in soil, where they benefit from filtered light and consistent warmth. They are adapted to temperatures that rarely drop below 60°F (15°C) and thrive in daytime ranges between 68°F and 85°F (20°C and 29°C).
Standard household temperatures typically fall within this narrow, comfortable range, which closely mimics the required climate for these warm-growing species. Placing these tropical varieties outdoors in temperate regions exposes them to two major threats: freezing temperatures and temperature shock. A sudden or prolonged drop in temperature below 50°F (10°C) can cause significant damage or even death to warm-growing orchids.
These tropical plants require consistent conditions to maintain healthy growth cycles. The stable environment of a home insulates them from the wide, unpredictable temperature swings common in most outdoor climates.
Key Environmental Needs for Indoor Cultivation
Light
Providing the correct illumination is a significant factor in promoting orchid growth and flowering indoors. Most orchids, including Phalaenopsis, prefer bright, indirect light, which imitates the light filtering through a dense forest canopy. Direct, intense sunlight can quickly scorch their delicate leaves, resulting in noticeable white or brown papery spots.
An east-facing window is often considered ideal, as it provides gentle morning light, while a shaded south or west window may also be acceptable if the sun is diffused by a sheer curtain. Insufficient light is usually indicated by dark green, floppy leaves and a failure to produce flower spikes. Growers can also supplement natural light with full-spectrum LED grow lights, ensuring the plant receives a consistent 12 to 14 hours of light daily.
Temperature Stability
Temperature control is a primary function of the indoor environment, and most household orchids thrive when daytime temperatures are between 70°F and 80°F (21°C and 27°C). A slight temperature difference between day and night is often beneficial, with nighttime temperatures ideally dropping by about 5°F to 10°F (3°C to 6°C). This gentle cooling is thought to help initiate the development of new flower spikes.
Warm-growing orchids must be protected from cold drafts, such as those from open windows or air conditioning vents, which can cause bud drop and stress the plant. Maintaining a minimum night temperature above 60°F (15°C) prevents root rot and leaf loss, especially when the plant is watered.
Humidity
Humidity is a challenging requirement for indoor orchid cultivation because most homes have relatively dry air, especially during winter. Orchids, particularly epiphytes, prefer humidity levels between 50% and 70% to prevent excessive moisture loss through their leaves and roots. While they can adapt to lower household humidity, supplemental moisture is often necessary for optimal health.
A simple method to increase ambient humidity is placing the potted plant on a humidity tray filled with pebbles and a shallow layer of water. It is important the bottom of the pot does not touch the water, as this can lead to root rot. Grouping several plants together can also create a beneficial microclimate by increasing the moisture naturally released through transpiration.
Conditions for Successful Outdoor Placement
While most orchids are kept indoors, some species and specific climate conditions allow for successful outdoor placement. Certain cool-growing orchids, such as many Cymbidium species, are more tolerant of lower temperatures and can be grown outdoors year-round in mild climates that do not experience hard freezes. These orchids require cool nights, ideally between 50°F and 57°F (10°C and 14°C), to set their flower spikes. In these suitable regions, they can tolerate temperatures dipping to 40°F (4.4°C), provided the cold is not prolonged.
For growers in temperate areas, the practice of seasonal placement, or “summering out,” allows tropical orchids to benefit from the natural air movement and brighter light of the warmer months. This is only viable once the threat of frost has completely passed, typically when nighttime temperatures consistently remain above 55°F (13°C). Orchids must be placed in a sheltered spot, such as under a tree canopy or covered deck, to ensure they receive filtered light and are protected from direct midday sun that causes leaf burn.
Outdoor placement increases the risk of pests, requiring careful inspection before the plants are brought back inside in the autumn. The potting medium will also dry out much faster outside, necessitating more frequent watering compared to the indoor schedule.