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Notebook · Guide 8 October 2026 · houseplants

Cymbidiums won't flower without a cold autumn

A cymbidium with lush leaves and no spikes was almost always kept too warm. Summer it outdoors, let it feel cool nights of around 13°C or below, and bring it in before frost.

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You bought a cymbidium in full flower, it finished, and since then it has made handsome grassy leaves and fat bulbs and not a single spike. That's the most common cymbidium story there is, and the fix is almost never a product. These are cool-growing orchids. They set their flower spikes in late summer and early autumn, and they only do it when the nights turn properly cool. A warm living room all year round keeps them growing and never flowering.

01At a glance

  • The trigger: cool nights from late summer into early autumn. The American Orchid Society puts the night figure at about 13°C (55°F) or below.
  • Outdoors: roughly June to mid-September, in a warm, sheltered spot in light shade. Harden it off first so the leaves don't scorch.
  • Coming in: before any frost. Then keep it cool and bright, ideally 10–14°C in winter.
  • Feed: high-potassium orchid feed through summer and autumn. Avoid high-nitrogen feeds from mid-August.
  • Light: the other big reason they don't flower. Good light all year, with shade only from strong summer sun.

02The summer-outdoors routine

  1. Harden it off in early June. Introduce it to outdoor light gradually, in a sheltered spot out of strong sun, so the leaves don't scorch.
  2. Stand it somewhere warm, sheltered and lightly shaded. Dappled light is ideal. The RHS suggests keeping it below 30°C in summer.
  3. Water and feed well. In growth, cymbidiums drink far more than a moth orchid. Let the bark dry slightly between waterings, and use rainwater if your tap water is hard. Feed with a high-potassium orchid feed at three waterings out of four, and plain water at the fourth.
  4. Leave it out as the nights cool. This is the bit people skip. Those cool late-summer nights are the signal to make spikes. The RHS window runs to about mid-September. The American Orchid Society says the plants will take near-freezing temperatures with a little protection, so there's no need to rush it in at the first chilly night.
  5. Bring it in before frost. Watch the forecast, and don't gamble on a clear, still night.

03Indoors while the spikes grow

Once it's inside, the job is to keep it cool and bright, not cosy.

  • Below 15°C while the spikes develop. The RHS says this helps prevent bud drop. A cool porch, spare room or unheated conservatory beats a warm lounge.
  • Don't move it about once buds form. Sudden swings, warm draughts and new positions are the usual reasons buds blacken and fall.
  • In flower, about 21°C is ideal, according to the RHS.
  • Water less in winter. Weekly or fortnightly is usually enough. Never let the pot stand in water.

04Why yours isn't flowering

Work down this list. The first two cover most plants.

  • Nights too warm in late summer. It spent the summer on a windowsill indoors. Next year, put it outside.
  • Too little light. The American Orchid Society says poor light is second only to warm nights as the cause. A useful tell: healthy leaves should be a light yellow-green. Dark grass-green leaves usually mean it wants more light.
  • Too much nitrogen late in the season. A leafy growth feed in autumn keeps it making leaves.
  • Recently divided. The RHS says newly divided plants usually take two to three years to flower again.
  • Buds formed, then dropped. Too warm while the spikes grew, or moved once buds had set.

05Repotting without losing a year

Repot only when the bark has broken down or the plant is bursting its pot. The RHS says at least every two years; the American Orchid Society says generally every two to three. Do it in spring, straight after flowering, so the roots recover before the next autumn. Use coarse orchid bark, never ordinary compost, and go up about 10cm in pot width. If you divide it, keep at least five healthy bulbs in each piece, as the RHS advises. The American Orchid Society says five or six, and never fewer than three.

Save your money
Don't buy a "bloom booster" for a plant that never felt a cool night. No feed replaces the temperature drop. Your garden provides it free.
Don't buy grow lights for summer. Outdoors in dappled light gives it far more light than any windowsill.
Collect rainwater for watering, especially in a hard-water area. It's what the RHS suggests where possible.
Don't overpot. About 10cm wider than the old pot is enough, and repotting only every couple of years.

Before placing it where children or pets can reach, check the safety flags on our cymbidium profile.

How we checked this

Every care and safety claim on this page is verified against horticultural and veterinary sources.

Sources: RHS — How to grow cymbidium orchids · American Orchid Society — Cymbidium culture

Checked 8 October 2026. If our advice ever conflicts with the RHS, believe them and tell us.