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Pleurothallids

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The Subtribe Pleurothallidinae contains 20+ Genera, so any recommendation of cultural conditions must be a generalisation, and conditions for a particular species should always be checked in the literature, if this information is available.

However, most pleurothallids grow as epiphytes in cloud forest, in cool, airy conditions at a high altitude. This gives us indications of the conditions we should be trying to reproduce in our greenhouses.

Thus, most plants require a minimum night temperature during the winter months of 10C (50F). This should rise during the daytime by about 4C (7F). During the summer, the night temperature will naturally be higher, but the daytime temperature should be kept below 30C (87F). Even this is too high for some species such as Dracula which should be kept below 26C (80F) or desiccation of the plant and flower spikes will occur. These plants also require a higher minimum winter night temperature of 13˚C (55˚F).

The plants should be kept well shaded from direct sunlight from as early as March until October, and certainly heavily shaded during the summer. This in turn will help keep the temperature down.

Most plants require a moist, humid atmosphere. For some, it is not sufficient to 'damp-down' the greenhouse floor, and the use of a humidifier to maintain a relative humidity of at least 70% is recommended. Plants growing in cool, dark cloud forest, where cloud surrounds the plants night and morning, would require a humidity of 90% at these times.

The plants are often found at sites exposed to the wind, so fans are another essential to keep the moist air moving and fresh. Air circulation also helps to minimise fungal growths which can be a problem in the damp conditions.

The plants need to be in a compost which retains moisture but is also free draining. A mixture of fine fir bark, Perlite and dried Sphagnum moss (3:1:1) can be used. This medium should be kept moist by watering with rainwater when required. Rockwool based media can be too wet and cause rotting of the plants.

A general fertiliser should be applied for three waterings, then washed through with plain water to flush out any remaining salts. The concentration should be about 300 μSiemens - i.e. not too concentrated.

Many pleurothallids flower successively on each flower spike so it is important to be sure that this is dead before cutting it off. Some spikes emerge from the plant in a horizontal direction, some even growing downwards through the compost, and these plants should be planted in wire-mesh baskets. The plants should be repotted each year, either in spring or autumn and this opportunity to inspect plant growth carefully should be taken.

The pleurothallids are a varied and fascinating group of orchids to grow and to enjoy.

Eileen Watson

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