Florescent Bulbs


I am very confused about the different ‘grow lights’ required for orchids. I am planning to mount florescent bulbs under shelves for Dendrobiums, Paphiopedilums, and Phalaenopsis. What kind and how many bulbs should I use? What duration should they be on? Scott M.


There is no question that natural light offers the best growing environment for orchids but there are times when other sources of illumination must be considered. Every house has a finite number of windows and an enthusiastic hobbyist can rapidly accumulate more plants than there is space for. Installing a sunroom or constructing a greenhouse for overflow plants is not always an attractive option, especially in today’s economy.

One relatively inexpensive solution is to retrofit a plant stand with ‘grow lights’ – bulbs that are specially designed for plants. Orchids, in particular, respond best to visible light at wavelengths of 390 nanometers for growth and 750 nanometers for blooming. Therefore, two bulbs are required and these are mounted side by side just above the height of the foliage – typically a few inches. Once an orchid starts to produce a flower spike, it must be removed from the shelf or the buds will grow towards the lights, eventually getting scorched or broken.

The distance between the bulbs and leaves is critical – too close and the foliage will burn, too far and the light will dissipate dramatically.

For a collection that consists entirely of young plants, only the bulb for growth is desired since seedlings are not old enough to bloom and do not need high frequency light.

Tropical plants reside near the equator where days are long so horticulturalists generally use timers in conjunction with the grow lights to mimic these conditions. A common recommendation for orchids is 14 hours of light and 10 hours of darkness.

Low light epiphytes such as Paphs and Phals will respond well to florescent grow lights which emit light levels in the 1000 to 2000 foot candle range. High light orchids, including Dendrobiums, will not be happy in these ‘twilight’ conditions – producing stunted leaves and few flowers. While there are sophisticated lighting systems to handle these plants, neophyte hobbyists are encouraged to stick to the forest bottom dwellers.



My Phalaenopsis had beautiful blooms which all wilted overnight after I left it by a bowl of apples. I moved the plant and within a few weeks the stem sprouted side branches which are starting to form buds. Is this normal? Should I have cut off the stem and waited for another one? Phoebe R.


One might wonder how a bowl of fruit could possibly affect the longevity of flowers? A little known fact is that aging fruit, including apples, avocados, bananas, melons, peaches, and tomatoes give off an invisible gas called Ethylene, which causes significant damage to certain plants including orchids. Leaves turn yellow, buds fall off, open flowers fold up. Other common sources of Ethylene are Propane heaters and Cigarettes. Wherever possible, keep notorious Ethylene producers separate from valuable plants!

In the event that a Moth Orchid drops its flowers prematurely or the stem is broken in half accidentally, there is the strong possibility that the plant will attempt to bloom again rather quickly from one if its many ‘nodes’ that reside along the stem. These ‘nodes’ often sprout secondary branches or keikis during normal operation but are capable of generating the main stem under dire circumstances. Such is the case when normal flowers fold early due to Ethylene. The plant is already geared up to bloom, instinctively tries again, and usually succeeds. 

Saturday, January 1, 2011 - 17:30