Odontoglossum (oh-DON-to-gloss-um), and their close relatives, make up this highly attractive group of orchids.  They include:  Miltonia, Brassia, Oncidium, Wilsonara, Cambria, Odontoglossum, Vuylstekeara, Maclellanara and Zygopetalum.

These plants are so closely related that it has been possible to cross breed between the families and, in so doing, produce more robust hybrid plants with larger more varied flower shapes and colours.  The hybrids tend to show more vigorous growth and withstand warmer conditions than their parent species. 

They originate from South America where they grow at high altitude as epiphytes amongst moist shady areas of the Andes. 

They are compact clump-forming evergreen plants with egg-shaped, slightly flattened pseudo-bulbs from which 1 to 3 leaves form and the flowering spikes are produced.

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, (not drafts).

Temperature:  Cool to intermediate, most hybrids are happy at a nighttime temperature of 10°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 10°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 on the leaves, the plant may be getting too much light.

Water:  Most orchids prefer free drainage and it is best to 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.  During the winter, if the temperature is low, you may water less often but do not let the bulbs shrivel.  Clean rainwater is preferred by the plant but you can use filtered tap water.

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

Air Humidity:  Odontoglossum need relatively high levels of humidity so moist air is essential.  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, therefore, Odontoglossums will benefit from repotting every other year after flowering.  The best time to do this is spring when the new roots and shoots are developing, but repotting can also be undertaken in the autumn.  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.  Suitable 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 of 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 or slightly to one side of the pot, (allowing room for new growth,) 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 2 weeks after repotting, allowing the plant to get used to the new compost.  Water as normal after this period.

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, thrip 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:  Odontoglossum 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, (not drafts).