Phalaenopsis (moth orchid)

Phalaenopsis (moth orchids) grow well in centrally heated rooms and have long-lasting flowers produced all year round. They are one of the most popular indoor orchids.

Phalaenopsis 'Kung's Green Star' displayed by McBeans Orchids. Hampton Court Palace Flower Show 2007. Tim Sandall/RHS The Garden

Quick facts

Common name Moth orchid
Botanical name Phalaenopsis
Group Houseplant
Flowering time All year round
Planting time Re-pot occasionally in spring to early summer
Height and spread 15cm-1m (6in-3ft) by 20-30cm (8in-1ft)
Aspect Bright light, but shaded from direct sunshine
Hardiness Tender, minimum 16°C
Difficulty Moderately easy

Cultivation notes

Light

Ensure good light levels in winter, as these are essential to encourage flowering. An east- or west-facing window would be ideal. Move to a shadier spot in summer and protect from direct sunshine. Occasionally wipe off the dust from the leaves with a damp cloth, as dust will block light from reaching the foliage.

Temperature

Phalaenopsis grows best in a warm environment. Provide night temperatures in the range of 16-19°C (61-66°F) and day temperatures between 19-30°C (66-86°F). Avoid draughts and fluctuating temperatures.

Flowering

Phalaenopsis produces flowers that last about three months (sometimes even longer) at any time of the year. Once the flowers have faded, cut the flowering stalk back to just above the second node (joint) visible beneath the spent flowers. A new flowering side shoot may develop.

If a plant is large and healthy but does not produce flowers in a reasonable time, then reduce the temperature by 5°C (8°F) for four weeks, and a flower spike will usually develop.

Watering, humidity and feeding

Water Phalaenopsis regularly throughout the growing season. Reduce watering slightly during the winter. Always keep the foliage dry, taking care not to splash the leaves when watering. Do not let the roots dry out completely, but avoid letting the plant sit in water. Mist the plant lightly in summer.

Feeding can be done regularly in the growing season – almost every time you water – but plants do need the occasional 'flushing out'. So, apply proprietary liquid orchid fertiliser with three waterings, but use only plain water (with no fertiliser) every fourth watering to ensure that any potentially harmful accumulations of salts are leached from the compost. Feed sparingly during the winter months.

Repotting

Phalaenopsis can be repotted at any time of year. Some notes on repotting your moth orchid;

  1. Clear pots are useful as an aid to watering as they enable you to see if the compost is still moist below the surface. Phalaenopsis' roots are also attracted to the light and prefer growing in clear pots.
  2. It is time to repot your plant as soon as it has become too large for its pot or when it has been in the same compost for 2 years.
  3. In the case of phalaenopsis repot when the roots are active and showing green tips.
  4. Always use a proprietary orchid compost.
  5. Remove the plant from its pot and work at the rootball with your fingers, untangling the roots and removing all of the old compost maintaining your orchid’s roots in good condition is essential to its successful cultivation.
  6. Snip off any diseased or dead roots with sterilised scissors or secateurs. These are brown, mushy, shrivelled or hollow in appearance.
  7. Shorten the remaining healthy roots, that should be white and firm, back to around 12cm (5in).
  8. If the roots comfortably fit into the old pot, then reuse it. When using a larger pot unnecessarily, the compost will stay wet for too long causing roots to rot.
  9. Hold the plant at the correct level in the pot and fill in the spaces around the roots with fresh compost, gently firming in as you go and ensuring the compost is pressed down firmly around the perimeter of the pot, so that finally, when the plant is lifted by its stem, the pot and compost is lifted with it and does not fall off. Loose compost will cause the plant to be unstable and damage the new root tips, stopping them from growing.
  10. Don’t bury the roots that are growing out into the air, as these will rot if confined in the compost.
  11. If the plant needs the support of a cane or two until its roots establish in the pot, insert them now. Finally, give the plant a thorough watering ensuring all the rootball is moistened.
  12. Drain the plant thoroughly and do not allow it to sit in water.

    Tipping out a moth orchid ready for repottingTrimming off old rootsRepotting the prepared moth orchid with fresh compostStaking the newly repotted orchid to keep it stable

    Propagation

    Sometimes small plantlets (keiki) appear from the nodes on the flower stems. Detach the plantlets when they have developed several good roots and pot them up in orchid compost. Water them sparingly at first, but mist them daily.

    Production of offsets can be encouraged by application of keiki paste (a specialist hormone preparation) to the nodes of the spent flower spike. Ordinary hormone rooting compound will not do.

    • With a scalpel make a vertical cut through the bract covering the node. Do not cut into the bud beneath
    • With tweezers pull away the two halves of the bract and apply a little keiki paste to the exposed bud
    • After six to eight weeks little plantlets may be produced

    Keiki paste can obtained from specialist orchid suppliers such as Ratcliffe Orchids.

    Cultivar Selection

    Many new hybrids are introduced every year, but most Phalaenopsis offered for sale are unnamed hybrids. Only specialist orchid growers will offer named species and hybrids. Newer introductions and recent hybrids (even if unnamed) tend to be easier to grow and bloom more frequently, but here are some species to try for the keen grower:

    Phalaenopsis schilleriana: Deep rose pink-flushed white flowers up to 8cm (3in) across, with silver-mottled dark green leaves.
    P. equestris: Clusters of 10-15 small pink flowers, each 2.5cm (1in) across, with fresh green leaves.
    P. cornu-cervi: Spidery yellow flowers spotted with dark red, each 2.5-3.5cm (1-1.5in) across, in clusters of about 12 blooms that open successively.

    Problems

    Phalaenopsis suffer from the same problems as other orchids, including mealybug, slugs and snails.

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