Zygopetalum (zi-go-pet-a-lum) are part of the Odontoglossum alliance and require similar conditions. 

They originate from tropical Central and South America, especially Brazil.  There are about 20 species found naturally from which many hybrids have been developed.

They are compact clump-forming evergreen plants with large egg-shaped pseudo-bulbs from which 1 to 5 leaves form and the flowering spikes are produced.  Flowers are quite often scented and long lasting.

Flowering:  The flowering season is usually during the autumn to spring with flower spikes growing from the new bulbs.  Individual flower stems may last for 4 to 6 weeks.

Successful flowering requires low temperatures and restricted watering during the winter, whilst maintaining relatively high humidity and very good ventilation.

Temperature:  Intermediate conditions are required for most hybrids with a nighttime temperature of 13°C-16°C and a daytime temperature of 18-24°C.  In summer, the maximum temperature should be around 24-27°C; if they are kept higher than this for any length of time they may not flower.  In winter, the temperature should be kept above 12°C; if they are allowed to get colder than this extra care should be taken to water less.

Note:  To help prevent flower and bud drop, keep plants away from drafts, radiators and other heat sources.

Light:  Good light in winter but during the summer months they need to be shaded from direct sunlight.  A north facing windowsill is ideal.  If you notice a red pigmentation to the leaves this may be an indication that the plant is getting too much light.

Water:  During the summer, keep compost evenly moist; this is the growing period when the plants are producing new growths.  In the winter, keep plants on the dry side and water sparingly, however, do not allow the pot to become so dry that the bulbs start to shrivel as this indicates the plant is stressed and using up its reserve energy.  Always water from the top, avoid getting water on the foliage and allow any excess to drain away.  Plants grow most actively during the summer when they should be watered once a week.  The autumn is the time of year when the pseudo-bulbs are ripening and, to encourage flowering, plants can be kept on the dry side until they start to flower.  Water more often when in flower.  Clean rainwater is preferred by the plant but you can use filtered tap water if necessary.

NOTE:  NEVER STAND THE PLANT IN WATER OR ALLOW THE PLANT TO BECOME WATERLOGGED.  This will cause the roots to rot and kill the plant. 

Feed:  Zygopetalum benefit from a weak solution of orchid feed, especially in the summer when it is best to feed every other watering.  Use a balanced orchid fertilizer, such as Ivens Orchids’ Orchid Feed.  During the winter, feeding once a month should be sufficient.

Air Humidity:  Relatively high levels of humidity are needed, (about 50-60%,) so moist air is essential; they also require good air circulation (not drafts) to prevent botrytis or bacterial/fungal infection.  The plant can be placed on a tray of moist pebbles to help with local humidity or keep in a room where humid air is present such as a bathroom, kitchen, utility room or conservatory.

After Flowering:  Cut off old flower stems near to the base.  Next seasons flowers will develop from new pseudo-bulbs.

Repotting:  Compost seldom remains in good condition for more than two years.  Zygopetalums will benefit from repotting every other year or when the plant is too big for its pot.  The best time to do this is spring when the new roots and shoots are developing but before flowering spikes have developed.  If the new growths are accompanied by flower spikes, repotting can be delayed until the autumn, or after flowering.  It is best not to repot in the summer.  It is important to use orchid compost which has a very open texture usually made from a mix of moss and bark.  Special orchid compost is available from Ivens Orchids.  Do not be tempted to use too big a pot; only pot up to a size sufficient to accommodate one year’s growth.  Older or larger plants can be divided by splitting large clumps into 4 or 5 bulbs.  Make sure the new plants have at least two bulbs with leaves and two older bulbs which can support the plant whilst it makes new root growth.  At the end of the season, it is normal to lose the odd lower leaf or two and new leaves should develop from the top of the pseudo-bulbs.  

Basic Repotting Technique:  Tap the plant out of its old pot and inspect the condition of the root-ball.  Shake off any decaying compost and remove all the dead, soft or black roots.  Remove any old black or soft bulbs with no roots but make sure to leave at least 2 bulbs with leaves and 2 older bulbs; these will help to support the plant should it become stressed after repotting.  Using a pot big enough to take a year’s new growth, support the plant in the centre of the pot while you feed fresh orchid compost around the root-ball.  Do not pack the compost in too firmly as these plants prefer a free draining pot.  Always dampen down the compost before potting and only water sparingly for the first 4 to 6 weeks after repotting, allowing the plant to get used to the new compost.  

Pests:  Prevention is always better than cure so look for good healthy plants to start with and keep them that way with a clean environment for your plants.  Throw away old, weak or infested houseplants and maintain good housekeeping in the greenhouse.  Most often seen pests are scale insect, aphids and red spider mite. All of these will weaken the plant if left unchecked.  The scale and aphids may be cleaned off with soapy water, (if found early enough,) otherwise treat with a specific systemic insecticide.

Buying Tips:  Always buy good quality orchids from a reputable supplier and look for clean healthy plants.  Unless you have ideal transportation and growing conditions, buying a plant with immature buds may be a mistake as some plants can be sensitive to being moved during the early stages of flower development. Look for plants whose flower buds look quite plump and ready to open. 

Special Notes:  Zygopetalums are cooler growing than most orchids so find a nice cool spot in the house well away from any heat source.  Try to find a cooler place to keep them when they are out of flower, still maintaining good humidity and ventilation.