Most orchids bought in the UK are phalaenopsis (moth orchids), and most of them stop flowering after the shop blooms fade and never rebloom. The cause is almost always light. Phalaenopsis will stay alive and green in dim conditions for a long time, but reblooming requires more light than most living rooms with north or east windows provide. Here is the honest guide to orchid light requirements.
Phalaenopsis light requirements
Phalaenopsis orchids grow as epiphytes on tree branches in tropical forests, where they receive dappled, filtered light from the canopy. In indoor terms this translates to bright indirect light. The target range for active growth and reblooming is 10,000 to 20,000 lux.
The useful diagnostic is leaf colour. Medium green leaves indicate correct light. Dark green leaves indicate insufficient light. Yellowish green or reddish leaves indicate too much direct light.
The ideal source is bright indirect light from an east or west window, or a south window screened by a sheer curtain. Direct harsh summer sun scorches phalaenopsis leaves. They are thin and have no tolerance for intense direct exposure, which distinguishes them from high-light orchid types such as cattleya.
The best window for orchids
East window. The classic recommendation for phalaenopsis. Gentle morning sun transitions to bright indirect light through the remainder of the day. Leaves stay medium green, and spikes develop reliably in autumn when the plant has received good light through spring and summer.
West window. Works well in spring, autumn, and winter. In midsummer the afternoon sun can be slightly intense, but placing the plant 30 to 40cm back from the glass handles this without any loss of useful light. A good all-year choice if the east window is occupied.
South window with a sheer curtain. Viable. The sheer reduces intensity to bright indirect, which suits phalaenopsis well. Without a sheer, the unfiltered south window in summer is too intense and leaves may bleach and scorch. With the curtain in place, a south window is one of the brighter options available.
North window. Marginally viable in summer only. In winter the light drops well below what phalaenopsis needs to rebloom. Most north-window orchids stay green and alive but never produce new spikes. If a north window is the only option, a small full-spectrum grow light can bridge the gap.
Light and reblooming
Orchids produce flower spikes in response to two triggers working together: a temperature drop (usually a 5 to 8 degree drop between day and night, typically occurring in autumn when windows are opened in the evenings) and adequate light accumulated through the growing season.
Without sufficient light from spring through summer, the plant does not build the energy reserves needed for a spike. The temperature drop alone is not enough. This is why orchids kept in low light all year sometimes produce a spike and then fail to repeat: the reserves were just sufficient once, but not reliably.
The sequence for a reliably reblooming phalaenopsis: adequate light from March to September builds reserves; an autumn temperature differential triggers the spike; the spike develops over 8 to 12 weeks; flowers open and last 8 to 16 weeks. To increase reblooming, move the orchid to the brightest available window from March to September, then position it near a slightly cooler window in September and October to encourage the temperature differential.
Other orchid types and light
Dendrobium. Generally needs more light than phalaenopsis. A west or south window with some direct morning or filtered afternoon sun suits most dendrobium types. They can handle 2 to 3 hours of direct morning sun without damage, which would be too much for phalaenopsis.
Cattleya and related genera. High-light orchids that need several hours of direct sun. South or west window directly on the sill, without the setback recommended for phalaenopsis. Cattleya is the most sun-tolerant of the commonly available orchid types and will actually underperform in the softer light that suits phalaenopsis.
Cymbidium. Higher light than phalaenopsis, suited to an east or west window or outdoor summer placement. Cymbidiums benefit particularly from being placed outside in summer in a sheltered, lightly shaded position. The combination of higher summer light and natural temperature differentials typically triggers reliable autumn flowering, which indoor-only cymbidiums often fail to achieve.
Reading your orchid's light signals
Correct light: medium green leaves that are firm and upright; new roots (silver-green with bright green tips) visible at regular intervals; new leaf growth in spring and summer.
Too little light: dark green leaves with a deep, almost glossy tone; no new root growth visible for several months; no spike after 12 or more months despite healthy watering; gradual leaf drop from the bottom upwards over time as the plant lives off its reserves.
Too much light: yellow-green or reddish leaves across the whole plant; bleached pale patches on the part of the leaf facing the window (scorch damage that does not reverse); limp or wrinkled leaves even when adequately watered, caused by heat stress from too much direct sun rather than a watering problem.
FAQ
My orchid bloomed for three months and then never again. What is wrong?
Almost always insufficient light for reblooming. The shop flowers were produced under controlled conditions with optimal light. At home, if the plant is in a north window or more than 1m from an east or west window, it does not receive enough light to build the energy reserves needed for a new spike. Move it to a brighter position for the next growing season and watch for a spike to develop in autumn.
How do I know if my orchid is getting too much light?
The leaves tell you. Phalaenopsis leaves that are yellowing or developing a faint reddish tinge are receiving too much direct sun. Pale, bleached patches on the sun-facing side of the leaf are scorch damage. Move the plant back from the window or add a sheer curtain. Leaves that are medium green and firm indicate correct light intensity.
Can I put my orchid on a bathroom windowsill?
Yes, if the window faces east or west. Bathrooms often have higher humidity from showers, which benefits orchids. The key is the window direction. A north-facing bathroom window provides inadequate light for reblooming. An east or west-facing bathroom window with adequate light works well and the humidity is a bonus.
My orchid has a spike developing. Should I move it to more light?
No. Once a spike is developing, the orchid is in flower mode rather than growth mode. Moving it risks dropping buds or reversing the spike development. Leave it where it is through flowering. After the flowers have finished and you cut the spike, resume positioning for maximum light for the next growing season.
Does the colour of the pot or growing medium affect light requirements?
No. The roots' need for indirect light is sometimes cited (orchid roots contain chlorophyll and can photosynthesize in clear pots) but this is supplemental at most and does not change the plant's light requirements at the leaf level. Use whatever pot aesthetics you prefer; light at the leaf canopy is what matters for growth and reblooming.