Our speaker this month was Dr Derek Copley, the holder of the National Collection of Odontoglossum, who gave a most entertaining and instructional talk on this genus which has now been included in Oncidium. He began by describing his background as a nuclear physicist and U.N. peace negotiator and that he was a purely amateur orchid grower, having started with windowsill plants. This lead to him joining the Bournemouth O.S. and meeting Keith Andrew, one of the leading hybridizers of the genus.
Odontoglossum is a South America genus of cool to intermediate growing orchids distributed along the High Andes from Venezuela to Peru. The first plant Odont.epidendroides was collected in 1802 and the genus was established by Karl Kunth in 1816. The name refers to the two tooth like calluses on the base of the lip. They have a wide altitude distribution from 600 ft. above sea level to 11,500ft with increases in the diurnal temperature change rising with the altitude. Between 6000 –7500ft the mossy forest gives high root humidity, while in the semi shade between 7500 and 9200ft the temperature range is between 72oF in daytime dropping to around 53o F at night. In this area several species are found growing as terrestrials. In the higher regions between 9200 and 11,500 ft. the temperature range is from 77oF to below 50oF with cool air movement.
Derek then described the set up of his 12ft x 10ft greenhouse that houses some 600-700 plants. It is insulated with bubble polythene and between mid March and October the roof is shaded with 50% green shade cloth and the sides treated with white shading. Humidity is increased by an electric heater blowing onto a dish of rainwater. A large roof fan and small fans at leaf level provide air movement. A minimum temperature of 530F is maintained all year, with addition heat for Paphiopedilums and Phalaenopsis being provided by placing them on a heated sand bed.
The plants are grown in a mix made up of 70% medium bark, 10% medium charcoal, 10% chopped sphagnum moss and 10% Perlite. The main growing period is between September and June, with growth stopping outside this time. Repot the plants every year when growth is vigorous. Die back will occur if left for longer. Any outbreak of mealy bug is treated with Provado, with a tip from Sally Mill to water the plants with Provado three times a year. Feeding is done using Orchid Focus feeds, with some foliar feeding at a weaker strength applied to the underside of the leaves.
The talk was illustrated with images of Derek’s greenhouse and both Ondontoglossum species and hybrids. Throughout the talk there was considerable discussion on culture together with questions at the end, which made for an extremely enjoyable evening.
Editor’s Note: Although Odontoglossum is now transferred to Oncidium it has been used in the above report in respect of the title of the talk.