Equitant Oncidiums

Equitant (Tolumnia) Oncidiums

Where most orchid growers would grow either Cattleyas, Dendrobiums, Paphiopedilums or Phalaenopsis as their favourite genera, the equitant Oncidium could be considered an ideal companion plant. I like to grow these orchids and will give you an idea of my growing methods.

They are small plants and so can occupy unused space in an orchid house. eg. hanging on the wall above Cattleyas and Dendrobiums. I use two methods for growing my orchids
(a) 3" x 2" virgin cork for small plants and 6" x 4" for larger plants.
(b) clay pots and red radiata bark (only lasts 12 months).

Cork. The method for attaching the plants to the cork is a follows:-

Lay the plant on the cork with the crown approximately 3/4" to 1" from the bottom. Place some sphagnum (about 1/8" thickness) over the roots keeping it away from the crown. With small telephone type wire or fishing line, tie the sphagnum to the cork. Using wire or fishing line, loosely tie the plant to the cork. (This saves the plant from falling forward when watering.) Drill an 1/8" hole in the top of the cork (approximately 1/2" from the top). Insert the wire hook and bend as per the diagram.

Clay Pots. I have used the 2" ‘short’ plain clay pots and seedling (bark and charcoal) mix with not a lot of success. I prefer to use a 2 1/2" (with approximately 1/4" bark) or 3" (with approximately 3/8" bark) clay pots rather than plastic pots. When watering, the clay pots will dry out quicker than the plastic pots. I also prefer to use straight red radiata bark.

Reasons why I grow equitants:-

1. With a number of plants, one can have them flowering all year around although the main seasons are Autumn and Spring.
2. The flowers are colourful and have a wide range from white, pink, purple, red, yellow and brown. Colour markings of unflowered seedlings are hard to predict and this is what increases their appeal.
3. Their cultural conditions are similar to Cattleyas and Dendrobiums, but their day to day needs are less demanding.

Growth Habit. The most commonly grown equitant Oncidiums are small, epiphytic plants which have small or non-existent pseudobulbs and three sided, fleshly leaves arranged in a fan shape. In nature, they grow on the outer branches of trees where they receive ample sunshine and free air movement. In this habitat, the plants dry off quickly after dew or rain.

Many of the species come from the drier region of the Carribean Islands where the average annual rainfall is 30-40". The Carribean area lies from 13^o to 28^o north of the equator (Brisbane is about 27^o south of the equator) and has a wet summer and a dry winter.

Temperature. They can withstand the extremes of 4^oC to 40^oC (for a short period of time) without any apparent ill effects. More ideal conditions would be 10^o to 30^oC for best results.

Watering. During Spring, Summer and Autumn, the plants can be watered every day or every second day depending on day temperatures. In Winter, less disease problems occur if the plants are watered twice a week or misted just enough to prevent the leaves dehydrating and becoming shrivelled. At all times, water in the morning so that the plants and the mounts or pots can become dry or just damp by nightfall. Overwatering or watering too late in the day can cause bulb and leaf rot which will rapidly kill the plant. I never water on an overcast day and in winter I try to water only the roots of the plants.

Light and Shelter. Bush or shade houses covered with shade cloth giving 50-60% shade (with heat and wind protection on the south and western sides) are sufficient in most areas, but in regions where sufficient rain falls, it may be advisable to provide a weatherproof area under fibreglass or plastic sheeting.

Fertilisers. If at all possible, I catch rainwater in a large drum and water and fertilise with it. When I run out of rainwater, I will fill up the drum with town water and let it stand overnight to let the chlorine evaporate off. I also use an electric pump with a hand operated spray.

September to March - Every third week, Nuform Growth Formula (from Primac) - Root Hormone. Every 5th day, I fertilise using Johnson’s formula (Australian Orchid Review September 1994).

Johnson Formula

Basically, you require 3 only 4 litre plastic bottles.

Bottle 1 Dissolve 1Kg calcium Nitrate in 4 litres of water
Application 2 ml per litre of water

Bottle 2 Dissolve 8 spoons (5ml plastic spoon) of magnesium sulphate (Epsom’s Salts) in 4 litres of water.
Application 15ml per litre of water

Bottle 3 Dissolve 4 spoons (5ml plastic spoon) of cholated iron in 4 litres of water.
Application 15ml per litre of water

Aquasol approximately 8 gms (1 1/2 5ml plastic spoon) per 20 litres of water

From April to the end of August, fertilise every 4th day - 2 weeks Aquasol (23 4 18) then 2 weeks of Phostogen (10 4.4 22.5).

Pests and Diseases. Mealy bugs and scale are my main problems which I control with Chemspray Ant Spider and Cockroach Killer. Take precautions against poisoning yourself while you are applying the chemicals.

Fungal diseases are uncommon, but soft rot can kill plants quickly. This is probably caused by water still being held in the ‘fan’ of the leaves. I spray with Mancozeb to try and control the spread of soft rot.

Percy Tesch

Reference Material

Paper by Dr Noel Grundon

Australian Orchid Review - September 1984.