Why does my moth orchid have no flowers?

On a moth orchid this is a healthy plant with glossy leaves, perhaps a new leaf each year, that goes through one or two seasons without sending up a flower spike. Sometimes it flowers once and then does nothing for a long time.

The most likely cause is light. The entry puts this plant in bright indirect light, and says a moth orchid in a dim corner keeps its leaves for years and never spikes. The leaves are the gauge: mid green is right, dark glossy green means there is not enough light, and a yellowish or reddish tinge means there is too much. The RHS says to keep moth orchids in bright light in winter to encourage flowering, with an east or west windowsill ideal.

To confirm it in a minute, look at the colour of the leaves and the position. A very dark green leaf, or a plant standing more than a couple of metres from a bright window, points to light. Then ask about temperature. The RHS says moth orchids like consistently warm conditions all year round, which is the second cause. The entry says it needs a few weeks in autumn when nights are about 5 degrees cooler than days to trigger a spike.

The third thing to rule out is feeding and the old stem. The entry asks for a weak orchid feed every second watering, and feed pushes leaf growth. And a stem that is still green after flowering may branch if it is cut back above the second node, as the entry describes.

The RHS says that a large, healthy plant that has not flowered for a while should be moved to a spot about 5 degrees cooler for a month or so, and that it should then send up a new stem. Expect the spike weeks to a few months after the change, not within a fortnight. A plant in too little light needs a full growing season in better light before you can tell.

What this plant wants

The fix

Move it to a brighter window, and give it a few weeks in autumn where nights are about 5 degrees cooler than days.

Read on

It will not flower

The same sign on any plant, with the causes in the order they are likely.

Moth orchid care

Light, water, feeding, repotting and the rest of the entry.

Check it in the diagnoser

Opens with the plant, the part and the sign already chosen.