Advice
RHS Help & Advice
Growing orchids - Cymbidium and Phalaenopsis
Orchids have a reputation for being difficult to grow. However, the most popular, Cymbidium and Phalaenopsis are two of the least demanding.
Cymbidium
Temperature: A minimum night temperature of 10-14ºC (50-57ºF) is required. It helps if plants have a spell outdoors from June to September to encourage flower-bud initiation. Gradually acclimatise plants to sunlight to prevent leaf scorch. While spikes are developing, night temperatures must fall below 15°C (60ºF).
Flowering: This can occur from November to May with flower spikes lasting roughly eight weeks. Support developing spikes with a cane, and cut them down to 5cm (2in) when blooms have faded.
Watering and feeding: From spring to autumn, water from above and allow excess water to drain away; compost should just dry out between waterings. Moderate feeding during the growing season is beneficial. Use a general purpose liquid feed at half strength every third watering. Then use only water the fourth time to ensure that harmful salts are washed out. In winter, reduce the watering and allow plants to dry out for a time.
Re-potting: Re-pot congested plants after flowering in spring. Don’t overpot plants. Some of the old pseudobulbs that have lost their leaves can be removed. Use a specially formulated orchid compost which is available at larger garden centres and specialist nurseries. When dividing plants, ensure that there are at least three or four healthy pseudobulbs per division.
Phalaenopsis - moth orchid
Position: Requiring bright, but not harsh sunlight - as this can cause scorch - Phalaenopsis are best placed on an east- or west-facing windowsill. Move them into a shadier spot during summer.
Watering: It is important to maintain the correct moisture levels. Regularly check the compost and when it starts to feel dry, run tepid water through the pot until it runs out of the bottom. Too little water can result in leaves withering whereas too much water will lead to bud drop, yellow leaves that fall away, and root rot.
Nutrients: To encourage growth, add liquid orchid feed to every fourth watering between late March and September. Increase humidity around plants by placing the pot on a tray of damp pebbles, and mist the leaves (but not the flowers) regularly.
Prolonging blooms: A flower spike can continue to bloom for up to three months. Once faded, cut the spike just above the second node (joint) beneath the spent flowers, and a flowering sideshoot may develop.
Repotting: Moth orchids only need repotting occasionally, when they have outgrown their container or when the compost has started to disintegrate. Being epiphytes (plants that in the wild cling to trees and rocks rather than grow in soil) they will usually sprout aerial roots. Always use specialist orchid compost (usually bark-based) which is available from most garden centres.
Further information
Orchid Society of Great Britain; e-mail: Val@micklewright.com
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Photographs: (top) Cymbidium hybrid from Eric Young Foundation, (bottom) Phalaenopsis Sussex Melody 'Cooksbridge Pink Lips'. Photographs copyright RHS.