By Metin A. Savignano

Reproduced from Volume 7 of the Journal of the Carnivorous Plant Society. First published Spring 1983.

When I started to build up my collection of carnivorous plants, I soon hit a problem that must affect many others who are not fortunate enough to own a greenhouse: all my well lit windowsills became full. So I turned to using artificial light, but unfortunately there is not much literature on this subject, and I had to gain my own experience.

Why and Where?

Growing CP’s under artificial light has several advantages. You can place the plants growing under artificial light almost anywhere. Another advantage is that indoor conditions are much more easily controlled. And being able to switch the light on or off at will, you can be growing or even flowering plants in the dead of winter. In addition, you can use artificial light on a windowsill to supplement daylight.

What Kind of Light?

The quality of light can vary considerably between the various sorts of artificial light lamps.

The ‘Grow-Lux’ tube was specially developed for growing plants. It has an odd, violet light, consisting mainly of red and blue light (these are the wavelengths needed for the plants to photosynthesise). Too much red light, though, will cause the plant to become tall and thin, while the blue wavelengths cause broad leaves and a generally bushy appearance; the Grow-Lux tubes combine the ideal combination of both red and blue light.

‘Coolwhite’ lamps have a lower percentage of red and blue light, particularly the red. As a result, it is a much less ‘powerful’ kind of lamp, although I have heard of CP growers who use it.

Should you intend to light a whole room for your plants, ‘Warmwhite’ lamps are very good. They are much brighter than the Grow-Lux tubes, although the levels of red and blue wavelengths are about the same. I have seen plants grow solely under these tubes, and they looked very healthy (Ref. 1). My own plants are grown under a mixture of Grow-Lux and Warmwhite lamps ina 1:1 ratio, and they seem to thrive.

A newly developed type of artificial light is provided by ‘Truelite’ lamps. They give off light with the same spectrum of wavelengths as sunlight. Thus, Truelite is the very best lamp for your plants, but costs about three times as much as either Grow-Lux or Warmwhite tubes!

How?

Adrian Slack proposes in his book (Ref. 2) that tubes should be installed directly above the plants, about 3 — 8 ins. (8 — 20 cm.) above them, depending on genus. Yet he also admits that this set-up is difficult to manage with the upright pitchered species of Sarracenia. It becomes even more difficult if you want to plant rosetted and upright plants together.

So it is best install the tubes at a fixed height, and for this the top of a CP terrarium is ideal. I use this method and am pleased with the results. However, as artificial light loses its power very rapidly with increasing distance, you will have to experiment with various numbers of tubes. With my own terrarium, the distance between the tubes and rims of the pots (ie soil surface) is 16 ins. (40 cm.), and this needs a tube every 6 — 8 ins. (15 — 20 cm). It’s also useful to cover the top of the tubes with a strip of aluminium foil, to reflect light downwards to the plants.

The light should preferably be switched on for 16 hours a day, as for summertime, and an automatic switch would therefore be helpful. It’s best to let the plants have a winter resting period by gradually shortening the photoperiod to 8 — 10 hours a day — the cold climate plants will prefer the shorter period, and the temperate plants the longer photoperiod. Apart from allowing plants to be grown all year round, artificial light also allows winter growing plants (the pygmy and tuberous sundews) to grow during the warmer season. In winter, cold climate species should be put in a plastic bag in the refrigerator, to allow for vernalisation (ie promote growth and flowering the next season).

The Plants

Most CP’s can be grown under artificial light — indeed, some prefer it to ordinary daylight. Although I have had difficulties with Darlingtonia, I have heard of someone who was growing it successfully with artificial light (Ref. 3).

The best CP’s to grow under artificial light are (in my experience): Byblis, Dionaea, Drosera aliciae, D. binata (all variants), D. capensis (especially the narrow-leaved form), Pinguicula caudata, P. gypsicola, P. moranensis, the smaller Sarracenias, Polypompholyx, and the easier terrestrial Utricularias. Those of you who are beginners at growing CP’s under artificial light should make their first attempts with one of the above species. Larger species, such as Darlingtonia, Sarracenia flava, and S. leucophylla, should be given their own high terrarium (although I prefer to keep them outdoors).

Other advice is to grow your artificially-lit plants like any indoor plant. However, I mentioned that CP’s grown this way like a high water level, which also increases their red colouration. In winter you should look scrupulously for fungal infections. To prevent these, let the compost become almost dry before you water your plants, and keep the humidity lower than usual (50 — 60%).

When you grow your CP’s in a terrarium you will notice that not many flies will get near to the plants, so you may have to feed your plants. One possibility is to raise flies especially for this purpose (Ref. 4), or to use dried Tubifex worms (Ref. 5). They are sold in cubes of dried worms, and after having broken them up into small pieces, you can put them onto sticky leaves or into pitchers. You might also feed your Venus’ flytraps the same way, although for this trap you should wet the pieces of worm first.

Happy growing!

Anyone who wishes to ask or correct me is welcome to write, and I will be pleased to discuss the problem:

Metin A. Savignano, Muehlrain 26, 7000 Stuttgart, Fed. Rep of Germany. (We would like to hear as well! — Editor).

References

• (1) Thomas Carow. Carnivorous Plant Newsletter vol. 11, pp 5—7.
• (2) Adrian Slack, ‘Carnivorous Plants’, p 184 (Ebury Press, 1979).
• (3) Jim Miller. Carnivorous Plant Newsletter vol. 9, p 39.
• (4) Douglas Wiggins, Jr. Carnivorous Plant Newsletter vol. 9, p 44.
• (5) Marc Deloach. Carnivorous Plant Newsletter vol. 11, p 5.