Why Moth Orchids Suit British Homes

Phalaenopsis — the moth orchid that appears in supermarkets and garden centres from autumn onwards — has a reputation for being difficult. It is not, provided you remember what it is. In the wild these plants are epiphytes, clinging to tree bark in warm, humid forests with their thick silvery roots exposed to moving air. They are not planted in soil and they do not drink from a reservoir of compost. Almost every problem people have with them comes from treating them like an ordinary houseplant in a pot of soil. Treat them instead like something perched on a branch, and a single flowering spike can last two to three months, often longer.

Getting Watering Right

This is where most orchids are lost, and it happens in both directions. Overwatering rots the roots; underwatering shrivels them. The trick is to read the roots rather than the calendar. Healthy roots are plump and green when wet, turning a silvery grey-green as they dry out. Water when they have gone silvery and the clear inner pot feels light.

In practice that means roughly every seven to ten days in summer and every ten to fourteen days in winter, though a warm south-facing room will dry a plant faster than a cool north-facing one. Water by taking the inner pot to the sink and running lukewarm water through it until it drains freely, then letting it stand for ten minutes before returning it. Never leave it sitting in a saucer of water.

• Use lukewarm water — cold water shocks the roots.
• Keep water out of the crown, where the leaves meet at the centre. Water pooling there causes rot within days. Tip the plant and dab it dry if you splash it.
• In hard water areas, rainwater is worth collecting. Limescale builds up on roots and leaves over time and is difficult to shift.
• Feed with a diluted orchid fertiliser at roughly quarter strength every second or third watering in spring and summer, and barely at all between November and February.

Light and Position

Moth orchids want bright, filtered light — the sort of brightness that makes you squint slightly, without any direct sun touching the leaves. An east- or west-facing windowsill is ideal. A south-facing window will scorch them in summer unless a net curtain or a sheet of greaseproof paper diffuses the light; move plants back from the glass between May and September. North-facing windows are usually too dim in winter but can work well in summer.

Leaf colour tells you a great deal. Deep, dark green leaves mean too little light and few flowers. Leaves with a reddish or purple tinge at the edges usually mean too much sun. Healthy mid-green, firm and glossy is what you are after. Aim for a room sitting around 18–24°C by day, dropping a few degrees at night, and keep plants away from radiators, cold glass after dark and draughts from doors.

Humidity in a Central-Heated Home

British homes in winter are dry — central heating can push humidity down to 30 or 40 per cent, while orchids prefer something nearer 50 to 70 per cent. A bathroom with a window, a kitchen windowsill away from the cooker, or a conservatory that does not overheat are all good spots. Otherwise, stand the pot on a tray of pebbles with water kept just below the top of the stones, so the roots sit above the water rather than in it. Grouping several plants together raises the humidity around them too.

Misting helps, but only in the morning, and only if water does not linger in the crown or between the leaves. In dull winter weather damp leaves are an invitation to fungal problems, so the pebble tray is the safer option.

Encouraging a Second Flowering

When the last flower drops, look at the spike. If it is still green and firm, cut it back to just above the second or third node from the base — a small dormant bud there can produce a side spike of flowers within a couple of months. If the spike has turned brown and papery, cut it off at the base and let the plant rest and grow new leaves.

To trigger a fresh spike the following season, the plant needs a spell of cooler nights. From late summer, find a spot where the temperature drops to around 15–17°C at night for three or four weeks, while keeping daytime warmth and light. Many people manage this simply by moving the plant to a spare bedroom or a cooler windowsill in September. Water a little less during this period, and expect a new spike to appear by late autumn.

Repotting, Roots and Common Problems

Moth orchids grow in chunky bark, not compost, and that bark breaks down after two or three years. When it turns dark and crumbly, or the roots are pushing over the rim, repot into fresh orchid bark in spring, in a pot only slightly larger. Snip off any roots that are brown, mushy and hollow — a clean pair of scissors is fine. Silvery roots growing out into the air are perfectly normal and should not be buried.

• Limp, wrinkled leaves: usually root loss from overwatering rather than thirst. Check below the surface before reaching for the watering can.
• Soft brown patches at the base: crown rot from water sitting in the leaves. Remove the damaged tissue, let the wound dry and water more carefully.
• Sticky residue or white fluff: mealybugs or scale. Wipe them off with a damp cloth and repeat weekly until they stop returning.
• A single yellow leaf at the bottom: nothing to worry about. Old leaves are shed naturally as new ones form at the crown.
• No flowers for a year: almost always too little light, or no cool night spell to initiate the spike.

Get these few things right — sparing water, gentle light, humid air and a cool autumn night — and a moth orchid will reward you for far longer than the six weeks most people expect.