TOLUMNIA (Toh-LUM-nee-ah)

The key to Tolumnias (equitant oncidiums) is understanding their natural habitat. The species are endemic to the Caribbean Basin with many confined to a single island. Most are found in intermediate to warm conditions on twigs exposed to bright light and air movement. Humidity is high and heavy dews or rain showers occur daily. Air movement is constant and plants never remain wet for long. Today's hybrids offer an astounding array of colors and patterns. Petite size and adaptability to a wide range of conditions make them suitable for under lights or on windowsills. And wait ... don't cut off that spike after the flowers fade. A secondary flowering will often occur and provide several more weeks of bloom.

Light

Bright, diffused light somewhere between that for phalaenopsis and cattleyas. Plants growing well but reluctant to bloom usually need more light. Tolumnias are fairly tough, but when moving plants to a higher light, do so gradually to prevent burning. This is especially true when moving plants outdoors for the summer.

Temperature and Humidity

Provide intermediate temperatures (55 to 90F) and relative humidity of 50 to 70 percent. Plants grown in windows or under lights benefit from summering outdoors where climate permits.

Watering is the most crucial aspect to success with tolumnias. Plants must dry out between waterings. Drying will be faster outdoors than on a humidity tray in a windowsill. Damp, cloudy days retard drying, bright, breezy days hasten it. Mounted plants can be misted daily because drying is rapid. Pots must be observed more closely for complete drying. The adage "if in doubt, don't water" applies here.

Do not mist or water during the heat of the day. Water trapped in the overlapping leaf bases can reach "cooking" temperatures and severely damage plants, especially tender new growth.

Fertilize with a balanced fertilizer applied every second or third watering at half to quarter strength. Accumulated salts can damage roots, especially those of mounted plants, so flush with plain water between fertilizer applications.

Potting and Mounting

Plants are best mounted. Twigs, cork bark, small wood or tree-fem plaques all work well. Moss or coconut fiber can be placed around the roots to help hold moisture. A daily light misting will help establish growth. If plants on mounts show a tendency to shrivel

despite regular watering, pare off some of the mount without disturbing the plant and set it in a clay pot (with no medium). This may afford the right amount of extra moisture. If conditions remain too dry, sift potting mix into the container around the base of the plant. The medium used should be porous and drain readily. Repot in spring when new growth begins to assure quick re-establishment.

Problems

Mealybugs, scale and aphids are typical pests and can be controlled simply by direct removal using a cotton swab soaked with ordinary rubbing alcohol. Wettable powder formulations of Malathion or Orthene (used according to manufacturer's directions) provide efficient control. Cygon seems to be toxic to the plants and should be avoided.

Divide and repot plants larger than 3- to 4-inch pots unless grown in baskets. Decline of the center of large plants invites bacterial or fungal problems.

Information gathered from the American Orchid Society www.aos.org