How to grow cymbidium orchids

What are cymbidiums?

These tender orchids flower from late autumn to spring, at a time of year when few other houseplants are in bloom. They produce arching stems that carry lots of large exotic flowers that are often speckled or streaked. There are lots of species and cultivars to choose from, with flowers of various colours. The flower stems sprout from a fountain of long, thin, evergreen leaves.

Choosing cymbidiums

Cymbidiums are available in two sizes:

• Standard – up to 1.2m (4ft) tall and ideal as a spectacular centrepiece for a bright room

• Miniature – 30–60cm (1–2ft) tall and easy to accommodate on a windowsill

There are many different flower colours to choose from, including pink, purple, ruby, yellow, lime-green, cream, white and more. The petals are often splashed or speckled with contrasting hues.
 
New hybrids are introduced every year, but most are sold unnamed. It is usually only specialist orchid nurseries that offer named species and hybrids. The newer introductions tend to be easier to grow.
 
Several cymbidiums have an RHS Award of Garden Merit, which means they performed well in RHS trials, so should do well in your home:

• Cymbidium erythraeum – fragrant green flowers with red speckles

• Cymbidium Dorothy Stockstill gx – spectacular red-maroon flowers on pendent stems

• Cymbidium lowianum – green flowers on stems up to 90cm (3ft) tall

• Cymbidium Sarah Jean gx ‘Ice Cascade’ – a ‘miniature’, with white, lightly scented flowers 

• Cymbidium Tiger Tail gx – very compact, only 30cm (1ft) tall, with yellow-green flowers

For more ideas and inspiration, visit the Glasshouse at RHS Garden Wisley to see all kinds of orchids in full bloom. Many of the RHS Shows also feature spectacular displays by orchid nurseries, and every spring the RHS holds an orchid show.

Buying cymbidiums

Cymbidiums are available from many houseplant retailers, including garden centres, florists and some supermarkets. They are also available from online plant suppliers and tropical nurseries. For the widest choice, go to specialist orchid nurseries.

Cymbidiums can be kept in their original pot for the first couple of years. They should then be repotted at least every two years, as bark-based orchid compost deteriorates over time. Vigorous plants may need to be repotted sooner if they are very cramped in their pot. The best time to repot cymbidiums is in spring, just after flowering but before new growth starts.

Choose a container that has enough room for two years’ growth (about 10cm/4in wider than the previous one). Avoid using a much larger pot (overpotting), as the compost will stay wet for longer, which can cause root rot. Transparent containers are not necessary, although they do allow you to see if the compost is still moist below the surface, which can help you avoid overwatering. You will also need a bark-based orchid compost.
 
Repotting is very straightforward:

• Carefully tip the plant out of its container. If it has made a large clump of ‘pseudobulbs’ (swellings at the base), divide into several new plants by sawing through the centre of the clump and the rootball with an old bread knife. Aim for at least five pseudobulbs on each new plant

• Remove all the old bits of bark compost from the rootball, gently untangling the roots if necessary

• Snip off any dead or rotten roots (these may be brown, mushy, shrivelled or hollow), then shorten the remaining healthy roots (these should be white and firm) to 15–20cm (6–8in) long

• Hold the plant in the new container at the level it was previously growing, and fill in the spaces around the roots with fresh bark-based orchid compost. Gently firm it in as you go, especially around the edges. If done correctly, when you pick up the plant by its stem, the container and compost should come with it and not fall away. Loose compost will cause the plant to be unstable and may damage the new root tips, stopping them from growing
• Finally, give the plant a thorough watering, ensuring the entire rootball is moistened. Let the water drain straight out – and don’t leave the plant sitting in water

​Check out our guides to repotting houseplants:

Location
Cymbidiums need good light all year round, especially in winter. But keep them out of strong summer sun.

Feeding

• In spring – apply a half-strength general liquid fertiliser or orchid fertiliser for three waterings, then use only water the fourth time to ensure any potentially harmful accumulations of salts are washed out

• In summer and autumn – switch to a high-potassium specialist orchid fertiliser, to stimulate flowering, for three out of every four waterings (using just water the fourth time)

• In winter – stop feeding altogether or feed only occasionally with a half-strength general-purpose liquid fertiliser or orchid fertiliser

Encourage flowering

• Flower stems start to grow in mid- to late summer, when plants need good light and a distinct drop between day and night temperatures. This is best achieved by moving plants outdoors, into a sheltered spot, out of direct sun

• Support developing flower stems with bamboo canes, as they can become top-heavy in flower. Insert the canes into the centre of the clump, so you don’t damage new roots near the outside

• To prevent bud drop, keep plants below 15°C (59°F) while the flower stems develop. Wait until the flowers have opened before moving plants into a warmer position, to put on display

• Each stem generally flowers for six to eight weeks. Ideally keep plants at about 21°C (70°F) during flowering. At higher temperatures the blooms may fade prematurely

• Cut stems down to the base after flowering

In mid- to late summer, ensure cymbidiums have good light and a distinct drop in temperature at night, to help initiate flowering

Cymbidiums need very little pruning – simply cut back the flower stems to the base once all the blooms have faded. 

It’s easy to make new cymbidium plants by dividing a mature clump when repotting in spring, especially if it has become overly large or if some of the pseudobulbs (swellings at the base) have died and turned brown.

Remove the plant from its pot, then cut it into several pieces by sawing through the centre of the clump and the rootball with an old bread knife. Each piece must have at least five healthy pseudobulbs. Discard older or shrivelled material. Pot up the new smaller plants individually into bark-based orchid compost. They will usually take two to three years to flower.

Cymbidiums are generally healthy and long-lived houseplants, but look out for the following:

• aphids

• mealybugs

• red spider mites

• slugs and snails (when outdoors in summer)