Orchid Care – The Right Amount of Light
Orchid Care – The Right Amount of Light
Measuring the amount of light
Along with temperature, light influences the most important life processes: germination, growth and the formation of flowers. The light requirements ‘of orchids tend to be determined by their temperature requirements in their natural environments.
Light requirements: Among other factors, adaptation to light has influenced the shape of orchids for millions of years. Even if you own a “nameless” plant, you can still work out its light requirements by studying certain characteristics of the plant:
- with large, fleshy leaves and no bulbs will not cope well with a lot of sunlight either. Example: ( ).
- Orchids with relatively tough leaves with large surfaces and relatively well-developed bulbs will not require direct sunlight until they reach the flowering stage and begin to open. Examples: , , , , .
- Orchids with narrow, tough, leathery leaves and large bulbs are genuine sunlovers. Example: .
- Orchids with narrow leaves, almost like stems, or with striated leaves, and with no bulbs are well adapted to great intensity of light. Example: striolatum.
How to measure light
In general, orchids thrive in light intensities of 6,000-10,000 lux. These values are normally to be found in windows. However, remember that even only 1m (3 ft) away from the window, the light intensity will be only a quarter of that near the window. An exact measurement of light can only be carried out with a luxmeter (obtainable from garden or photographic suppliers).
The best window position
Once you have made sure that the window is not open to the sky nor obscured or overshadowed by trees or other houses, the following guidelines can be accepted:
- East- and west-facing windows (3,000-5,000 lux) are the best positions.
- North-facing windows (800-1,000 lux) are really only suitable during the very light summer months and even then only for species that can cope with lots of shade.
- South-facing windows (up to 20,000 lux) are perfect during the winter. During the spring, summer and autumn, however, they will have to be provided with shade using curtains, blinds, sheets of tissue paper or with the help of neighbouring plants: during early spring between 11 am and 4 pm; from early summer onwards between 10 am And 6 pm.
The more humid and airy the position in which an orchid is placed, the lighter and warmer it may be.
Light from the mains
Even in a north-facing window or in a dark corner of a room, orchids will thrive with artificial lighting. Do remember, however, that ordinary light bulbs will not supply the right light for plants! I recommend special plant strip lights, two of which can be installed at intervals of 6 cm dust over 2 in) about 50 cm (20 in) above the orchids. Ask a professional electrician to install these and also have a timer switch fitted so that the lamps can be turned on and off on demand.
An alternative to this form of lighting is attractive hanging or wall lamps. They can be installed individually or in rows. As these kinds of lamps will require special fixtures, you should, again, get an electrician to install them for you. One hour of additional illumination with these lamps will cost only a few pence.
Only buy lamps that are resistant to splashes with water and make sure that they carry the British Standard kitemark. All electrical installations should be carried out by a professional electrician.
Artificial light — when and for how long?
The sum of natural and artificial light should not exceed 14 hours, otherwise your orchids will go on strike when it comes to flowering, just as they would if they were receiving too little light. Turn on the plant lamps:
- if you grow your orchids in a cellar, for a maximum of 14 hours per day
- on sunny autumn and winter days in the mornings and afternoons
- on dull autumn and winter days for 12 hours during the daytime.
Plant lamps give a real boost to freshly repotted orchids or those damaged by too much shade. If you own only one lamp, give the orchids a “light bath” if you are trying to coax them to flower.