The moth orchid is one of the most widely bought houseplants in Ireland, and one of the most frequently abandoned. People buy them in flower, enjoy weeks of those extraordinary blooms, and then watch the flowers drop one by one until they are left with a bare spike and a handful of leathery leaves. At that point, most plants end up on the windowsill in a kind of horticultural limbo, neither dying nor doing anything in particular. The truth is that this moment, when the flowers have gone, is exactly when the real care begins. Get it right and the plant will flower again. Get it wrong and it will sit there indefinitely, alive but going nowhere.

Moth orchids, known botanically as Phalaenopsis, are epiphytes in their natural habitat. They grow anchored to tree branches in the forests of Southeast Asia, with their thick roots exposed to warm, humid air rather than buried in soil. Their roots absorb moisture from rain and mist as it passes, then dry out before the next rainfall. This rhythm of wet and dry is fundamental to the plant's health, and it is almost the exact opposite of how most people water them. Overwatering is the single most common cause of failure, not underwatering. If the roots are sitting in wet compost for extended periods, they begin to rot. A plant with rotting roots cannot absorb water or nutrients regardless of how much you give it, which is why a neglected moth orchid on a dry windowsill often outlasts one that is watered weekly with the best of intentions.

The correct approach to watering is to observe the roots rather than follow a schedule. Most moth orchids are sold in clear plastic pots, which is not an accident. The roots are photosynthetic and need light, and the transparent pot allows you to see exactly what is happening beneath the surface. When the roots look silvery or pale, take the pot to the sink, run tepid water through it thoroughly for thirty seconds or so, allow it to drain completely, and return it to its position. Never leave the pot sitting in a saucer of water. In an Irish home through the winter months this might mean watering every two to three weeks. In summer, or in a warmer room, it might be more frequent. The plant will tell you when it is ready if you learn to read the roots. One important note on water quality: softened water should never be used on orchids. If your home has a water softener, use water from an outside tap or collect rainwater instead. Irish rainwater is ideal, and there is rarely a shortage of it.

Light is the other critical factor, and in Ireland it requires honest assessment. Moth orchids need bright, indirect light to flower reliably. An east-facing windowsill works well through most of the year, catching gentle morning light without the intensity of afternoon sun. A south or west-facing window in summer needs some screening or the leaves will scorch, showing as bleached or papery patches that do not recover. In winter, when Irish light levels drop considerably, moving the plant to a south-facing sill and removing any screening is often necessary just to give it enough light to sustain itself. A plant in a dark corner of a room through a grey Irish November and December will not flower the following season. If your windowsill gets cold at night when the curtains are drawn, move the plant behind the curtain or place a sheet of card between the pot and the glass. Moth orchids dislike cold draughts and temperature fluctuations far more than they dislike slightly lower light.

After the flowers drop, cut the spike just above the second node from the base. A healthy plant will often produce a secondary spike from that point within six to eight weeks.

Getting a moth orchid to flower again is where most people lose patience, because it requires a temperature drop rather than a change in feeding or watering. In their natural environment, orchids experience a drop in night temperature in autumn that triggers the production of a flower spike. You can replicate this in an Irish home by moving the plant to a cooler room or an unheated hallway for two to three weeks in September or October, somewhere that drops to around 16 degrees Celsius at night, then returning it to its usual warm position. Within six to ten weeks a new spike should begin to emerge from between the leaves near the base. When you see it, stake it loosely from the outset so it develops in the direction you want. Do not stake it tightly or move the plant once the spike is forming, as the buds orient themselves toward the light source and turning the pot at that stage can cause them to develop unevenly. When the flowers finally open, do not move the plant at all if you can avoid it.

Feeding a moth orchid should be light and infrequent. These are not hungry plants. A dilute orchid fertiliser, applied at half the recommended strength, every three to four waterings during spring and summer is sufficient. Do not feed in winter when the plant is resting, and do not be tempted to increase feeding to encourage flowering. Flowering in this plant is triggered by temperature, not nutrition. Excess feeding leads to a build-up of salts in the bark compost, which damages the roots. If you notice the root tips becoming brown or shrivelled despite adequate watering, flush the pot thoroughly with plain water to clear any salt accumulation before feeding again. Repotting should happen every one to two years, not into a larger pot but into fresh bark compost. Moth orchid roots need air as much as moisture, and old bark that has broken down into a dense, compacted mass no longer provides the drainage and aeration the roots require. When repotting, trim away any soft, brown roots cleanly and position the plant so the base sits at the surface of the fresh compost rather than buried within it. If you would like specific advice on positioning, reflowering or diagnosing a problem with your orchid, tell me about your situation and I will give you a direct answer.