What makes a number of orchid genera ideal house plants is their tolerance of lower light levels eg Phalaenopsis, Paphiopedilums, and Odontoglossum Intergeneric hybrids. Cymbidiums require higher light levels to flower and therefore are better in a heated greenhouse.
At the end of February orchids require shading from direct sunlight; the shading must be removed gradually, at around about the beginning of October as an Indian Summer may cause leaf burn.
From October to the end of February, Paphiopedilums, Miltonias and Odontoglossums will tolerate direct sunlight; Phalaenopsis, however require some shading all the year round, as they can be sensitive to full sunlight.
Orchids generally need re-potting every year, (large plants every other year), if they are grown in bark based compost. The usual time to re-pot is after flowering or springtime, prior to the growing season.
Re-pot Odontoglossums when the new growth is 2 – 3 inches high. Over potting is one of the biggest orchid killers; if in doubt re-pot the plant back into the original pot.
Remove most of the old compost from the roots, trim the roots and cut off any black leaves or rotting pseudobulbs. In the case of Miltonias, Odontoglossums and other Pseudobulbous orchids, keep the plant limited to 2 or 3 bulbs + the accompanying new growth. Any extraneous back bulbs can be removed with a sharp knife.
If the plant has outgrown the present pot, then it can be ‘dropped on’ into a pot one size larger. It is best not to disturb the plant too much, though some roots and compost may have to be removed.
The new growth in most cases should be placed as near to the centre of the pot as possible. In the case of Miltonias and Odontoglossums give the new growth a thumbs-width to grow into (this is a good guide to choosing the correct size of pot).
Slugs and Snails Common due to moist atmosphere. For control use products containing methaldehyde.
Red Spider Mite, False Spider Mite The appearance of which is enhanced by low humidity and dry cultural conditions. Clean your plants with soft soap, spray them with S B Plant Invigorator, Provardo or proprietry bug gun.
Scale and Mealy Bug Difficult to detect as they hide in inaccessible places.
Not easy to eradicate , clean the plants regularly with soft soap or dilute methylated spirits. Spray with S B Plant Invigorator , Provardo or other insecticide bug gun. Test these first to check they are not phytotoxic.
To prevent crown rot make sure water does not collect in the crown of the plant. Water early in the day to ensure that any water that has collected in the crown will dry out before night time. If bacterial rot is only in a portion of the leaves it can be cut out with a sterile knife or blade and fungicidal powder sprinkled on the wound to prevent secondary infection.