Orchids (Cymbidium, Oncidium, Paphiopedilum, Phalaenopsis)

Orchids are now our most popular flowering houseplant. This isn't that surprising, since they are relatively easy to grow - if you give them the right conditions - and many of them flower for many months on end.

The orchid family (Orchidaceae) consists of literally tens of thousands of different species and varieties, which grows year on year as there are lots of avid hybridisers producing new varieties.

Luckily, only a few species are available to buy, which makes things much simpler for us when choosing which plants to grow. The commonest are Cymbidium, Oncidium, Paphiopedilum (slipper orchids) and Phalaenopsis (moth orchids). Cymbidium and Phalaenopsis are the most popular.

In their native habitats, most orchids are tropical plants that live as epiphytes - this means they grow on trees and between rocks, not directly in the soil. This is why they are grown in a specific orchid compost, mainly based on bark.

 
How to grow orchids
Cultivation

Most orchids, certainly the common ones we grow, prefer bright but diffuse light. Avoid strong, direct sunlight, so if you are growing them on a south-facing windowsill make sure it is shaded.

Cool-loving orchids, such as Cymbidium, Dendrobium and Oncidium, need a minimum winter night temperature of 10C (50F). Paphiopedilumprefers a minimum temperature of 13-15C (55-60F), and Phalaenopsis needs a minimum temperature of 18C (65F).

Avoid placing orchids near heat sources, such as radiators.

Many orchids produce aerial roots, which are generally silver-green in colour. These take in moisture and help the plant ‘breathe’. Never cut these off and do not cover them with compost.

 
Planting orchids

Orchids should be grown in pots filled with an open, free-draining specialist orchid compost.

They prefer to be slightly potbound, so only re-pot when the roots fill the pot. Always use a pot that is only 1 or at the most 2 sizes larger than the current pot. Don't bury the large aerial roots in the compost as this can result in rotting.

However, it is usually a good idea to replace the compost every 2-3 years, as it can break down and cause problems. Carefully remove as much of the old compost as possible, but without causing any damage, and repot in the same pot.

 
Suggested planting locations and garden types

Houseplant, indoor plant, summer patio plant.

 
How to care for orchids

Orchids usually suffer if over watered. In spring and summer, water them around once a week or so, using tepid water. Water from above and tip out any excess water that collects in the saucer. Or plunge the pot in a sink of tepid water for no more than a couple of minutes and allow to drain.

They can also suffer if overfed, which burns or damages the roots. Use an orchid feed and follow the instructions carefully. A foliar feed spray is often a very effective way to feed.

Orchids need high air humidity, so mist the leaves and aerial roots daily. Or stand the pot on a wide saucer filled with gravel or hydroleca, which is kept damp. Remember to keep the saucer topped up with water, but not so it is in contact with the bottom of the pot.

Many orchids need a resting period during the winter, so reduce watering and stop feeding unless the plant is flowering.

Problems
  • Orchids may be susceptible to the following problems.
  • Overfeeding
  • Over watering
  • Sun scorch
Ultimate height

From 15cm (6in) to 90cm (3ft)

Ultimate spread

From 10cm (4in) to 90cm (3ft)

Time to ultimate height

5-10 years

Soil PH

Neutral

Moisture

Moist but well-drained