Orchids have a reputation for being difficult, but the familiar moth orchids sold in supermarkets and garden centres can live and flower for many years. Their care becomes much simpler once you understand that they don't grow like ordinary houseplants. Many have roots adapted to gripping tree branches, so burying them in dense potting compost is a common way to damage them.
This guide focuses on Phalaenopsis, or moth orchids, because they are the most popular indoor orchids in Britain. Other orchids, including cymbidiums and dendrobiums, have different requirements. Check the plant label before treating every orchid the same way.
Choose a healthy orchid to begin with
Look for firm, green leaves and roots that appear sound rather than black and mushy. A clear inner pot can help you inspect the roots. It's normal for a moth orchid to produce thick aerial roots that arch out into the air.
Choose a plant with several healthy flowers and, if you want a longer display, some unopened buds. Avoid plants that have spent a frosty night by an open shop entrance. Sudden cold can damage buds even when the leaves still appear healthy.
The best light for orchids
Moth orchids like bright but filtered light. An east- or west-facing windowsill often works well. Strong direct summer sunshine through south-facing glass can scorch the leaves, leaving pale or brown damaged patches.
Deep shade creates a different problem: the plant may survive but flower poorly. Move a struggling orchid to a brighter place gradually rather than placing it in intense sunlight without warning.
The Royal Horticultural Society recommends keeping moth orchids warm, generally above 16°C, and avoiding cold draughts and temperatures that fluctuate dramatically near doors or radiators.
What compost should you use?
Ordinary dense multipurpose compost is usually unsuitable for a moth orchid. These orchids need an airy, bark-based orchid growing mix that provides space around the roots while retaining some moisture.
Many are sold in clear plastic inner pots. These make it easier to see root condition and judge when watering is necessary. Decorative outer containers are fine, but take the orchid out to water it and ensure the inner pot drains completely.
Do not bury aerial roots simply because they look untidy. They are part of the plant's normal growth. Equally, don't force a mass of thick roots back into a container that is too small.
How often should you water an orchid?
Watering frequency depends on temperature, root condition and how quickly the bark dries. A common starting point is to check weekly during active growth, reducing the frequency in cooler, darker weather.
Examine the roots and potting mix. Plump green roots generally indicate moisture, while pale silvery roots may suggest that watering is due. The bark should approach dryness without the root system becoming severely dehydrated.
Run tepid water through the pot or briefly immerse the inner container, then let it drain thoroughly. Never leave the orchid sitting in a deep pool of water inside its decorative cover. Wet roots that cannot breathe may rot.
Avoid leaving water trapped in the centre of the leaf crown, where it can encourage decay. If water collects there, tip it away gently.
Humidity and temperature
Moth orchids appreciate ordinary comfortable indoor warmth and moderate humidity. They dislike cold draughts, especially around flowering time. Keep them away from radiators that produce dry blasts of hot air.
In a very dry room, a humidity tray or humidifier may help, but the roots still need drainage and the air shouldn't remain stagnant. Repeated misting is not a substitute for watering the roots properly.
If you move an orchid from a shop or conservatory into your home, it may shed a few buds while adjusting. Protect it from abrupt temperature changes and give it stable conditions.
Should you feed orchids?
Orchid bark contains relatively little nutrition, so a suitable specialist orchid feed can help during active growth. Use a weak solution at the frequency recommended on its label. Strong fertiliser can damage sensitive roots.
Feed less during periods of slow growth, and don't assume a plant without flowers needs an enormous dose. Light, root health and temperature have a major influence on flowering.
What to do after an orchid finishes flowering
A fading flower spike doesn't mean the orchid is dying. Once the flowers drop, inspect the stem. A healthy green spike may produce a new side branch from a node below the old flowers, although results vary.
Some growers cut a green stem just above a suitable lower node to encourage another display. If the stem turns brown and dry, cut it back carefully near its base. Use clean secateurs and avoid injuring leaves or roots.
The plant may need several months to produce a new spike. Keep it in good light and continue ordinary care. Don't repeatedly cut healthy leaves or repot immediately just because the last flower has fallen.
How to repot a moth orchid
Repot when the bark has broken down, drainage has deteriorated or the root system has become too congested. This may be every couple of years, depending on conditions.
Gently remove the old mix and examine the roots. Firm healthy roots can be kept; clearly dead, hollow or rotting material may be trimmed away with clean scissors. Choose a slightly larger orchid pot if necessary and surround the roots with fresh bark-based mix.
Repotting is often easiest when the plant isn't carrying a heavy display of flowers. Work patiently: orchid roots can be surprisingly brittle when handled roughly.
Why are my orchid leaves yellow?
One older leaf turning yellow occasionally can be part of normal ageing. Multiple yellow leaves, mushy roots or a deteriorating crown suggest a more serious problem.
Overwatering is a frequent cause. If the roots have rotted, the plant may look thirsty despite wet compost because it can no longer absorb water. Inspect the rootball before applying more water.
Direct summer sun can cause pale scorch marks, while cold exposure may damage leaves or buds. Look at recent changes in the plant's environment as well as what the leaves look like.
Why won't my orchid flower again?
Light may be insufficient, especially during a British winter. Move the plant into brighter filtered light where possible. Some moth orchids respond to a modest difference between day and night temperatures when initiating new flower spikes, but avoid exposing them to damaging cold.
Check the roots and bark condition, too. A plant using its energy to recover from rot may not be ready to flower. Patience is important: successful care is measured in months rather than days.
Common pests and problems
Mealybugs and scale insects: Look for cottony deposits or small attached bumps around leaf joints and flower stems. Isolate affected plants and treat using appropriate houseplant guidance.
Shrivelled roots: Check for prolonged drought or dead roots. Rehydrate sound roots cautiously and adjust watering.
Bud drop: Cold draughts, sudden moves and temperature changes are common triggers.
Soft crown: Water trapped between leaves may contribute to rot. Keep the crown free of standing moisture.
Keeping your moth orchid healthy
Keep the orchid in filtered light, use bark-based orchid compost and water only when the roots and pot suggest it is needed. Feed gently during growth and let the flower spikes follow their own cycle.
A moth orchid doesn't need complicated tricks. Stable warmth, healthy airy roots and patience are what keep it alive long after the supermarket flowers have faded.
Sources
Royal Horticultural Society: How to Grow Moth Orchids and Moth Orchid Genus Guide.