Orchids are shade-loving plants, and while they are growing they need the equivalent of the dappled sunlight they would receive growing in the tree canopy of their natural home. Too much light during the summer will harm the plants by turning the foliage a light green-yellow.

A useful piece of equipment is a maximum/minimum thermometer, or even several, which can be placed close to the orchids and the temperatures noted. In a greenhouse, it becomes difficult to grow orchids from these three ranges together in one place. What suits one group will not suit another, and you will find that inevitably some orchids will suffer from being too cold or too warm. An ideal situation is to divide a greenhouse into two or three sections, depending upon which orchids you wish to grow.

The cool-growing orchids are the largest group, and these include cymbidiums from the Himalayas, odontoglossums from the Andes, and many other genera, most of which are high-altitude plants, coming from elevations as high as 2,500m (8,000ft). They are often subjected to cold nights that drop to freezing, but at high altitudes the air is thinner, and occasional frosts do them no harm. In cultivation, we grow these orchids in a temperature band that rises from 10C (50F) minimum to 30C (86F) maximum.

After flowering and before the new growth starts, Calanthe pseudobulbs can be taken out of their pot and left to dry until the new growth is seen.

The summer daytime maximum should not exceed 30C (86F), which is a comfortable temperature for the orchids. Above this, the plants will inevitably become stressed, and growth will slow down and may even come to a stop. Overheating can be difficult to prevent in a greenhouse and needs to be controlled by sufficient ventilation, shading and damping down.

After their winter’s rest, orchids commence their new growth in the spring. Repot the plants as soon as this happens and before the new roots start at the base.

Calanthes are deciduous orchids which produce their flower spikes at the end of the growing season, as the plant is about to shed its leaves and rest. The flowers will appear while the plant is leafless.

Orchids can be fed at all ages, from young seedlings and propagations to adult plants. Feed only healthy plants, however, because they have the ability to absorb and convert the chemicals. Do feed plants that are sick or have lost their roots. New roots that appear may be burnt by the residue remaining in the compost (growing medium). For the same reason, do not feed orchids that are resting. Their roots will have become inactive, and the chemicals will remain in the compost where they may cause harm as the plant sans into growth in the spring.