GROWING LOCAL ORCHIDS IN ROCKWOOL

Abstract

Epiphytic orchids, Oncidium Gower Ramsey and Dendrobium Ekapol Red, and terrestrial orchids, Spathoglottis plicata and Bromheadia finlaysoniana were grown in three different ratios of rockwool - 25% repellent:75% absorbent, 75% repellent:25% absorbent and 50% repellent:50% absorbent over a period of three months. Hoagland solution was supplied twice weekly. Growth parameters such as number of ppseudobulbs, shoot height, fresh weight, dry weight, etc. were recorded. Generally, all the orchid seedlings established well in rockwool under the various treatments. There was, however, a marked difference in growth of the epiphytics compared to the terrestrials. Oncidium orchids in rockwool of ratio 25% repellent:75% absorbent grew best. A further experiment studying the influence of concentration of Hoagland solution and its frequency of application for Oncidium seedlings grown in 25% repellent:75% absorbent were carried out. Results indicated that plants supplied with a quarter strength Hoagland solution every alternate day performed best. It was observed from the kinetic uptake of minerals by the roots of Bromheadia and Oncidium, that the terrestrial orchid absorbed a much greater percentage of nitrate and phosphate compared to the epiphyte.