Insufficient natural light — in some instances, a complete lack of it — give many would-be indoor gardeners a major headache, as only a limited range of houseplants will survive in unnatural light conditions.
There has, however, been a major step forward in growing many houseplants — as well as some vegetables and herbs — using nothing more than artificial lighting. With careful judgment, combined with experimentation, this can change the growing game completely for those living in homes having little or no natural sunlight to brighten the days.
Some plant species such as Pothos (money plants) and Sanseveria (mother-in-law’s tongue) are known to grow perfectly well without any natural light at all but others, especially flowering houseplants, rarely survive more than a few days of sunlight deprivation. Installation of suitable artificial lighting can change this.
Indoor plants perk up living spaces but need proper light, humidity and temperature to thrive
Basically, in order to thrive, plants photosynthesise sunlight into food. Sunlight comprises blue wavelength light for foliage growth, red wavelength light for flowering and fruiting, and green wavelength light is largely reflected back off plants — because of this the leaves on the whole are green.
Hence, when replacing sunlight with artificial lighting, remember this artificial light must produce blue and red wavelength lights for satisfactory plant growth and health. It is not just a matter of simply utilising already fixed light-sockets/fittings, flicking the switch and leaving the lights on for a few hours each day as, along with humidity levels and temperature control, the distance between plants and artificial lighting is also of prime importance.
It is not necessary to invest in the costly ‘grow light’ type of light bulbs/tubes which are rapidly increasing in popularity in some parts of the world if you are growing ‘ordinary’ houseplants. For these, as long as you select suitable light bulbs/tubes and place then correctly, you have a pretty good chance of success.
Indoor plants — especially those grown under artificial lights — tend to need watering more regularly than their outdoor counterparts, so please do pay strict attention to this.
It is important to remember that plants and humans see and use light very differently: a drawing room which gets enough natural light for a human to sit and read by, for example, may very well be lacking in enough light for healthy plant growth. But judicious placing of one of the light types detailed below could very well transform such a room — or another room in the house/apartment — into a growing space that plants adore.
Fluorescent light bulbs/tubes are the most economical to use and, being relatively cool, they can be placed approx 12 inches away from plant foliage without causing leaf burn or other damage. White light tubes/bulbs contain the necessary blue and red wavelength light with some green wavelength light for good measure. A 60-watt fluorescent tube light, suspended 12 inches above the plants will provide equal light to an area measuring about 3ft x 3ft and needs to be kept on 18 hours a day when used as total replacement for sunlight.
Incandescent lights radiate far more heat than fluorescent ones and cost more to run but as they produce a higher percentage of red wavelength light they are invaluable in encouraging plants to flower. A 60-watt incandescent light suspended three to four feet above plant foliage will light an area of three to four square feet and, for ‘ordinary’ houseplants, needs to be on for 18 hours a day if it is the sole light source.
Halogen lights are variable: some do provide the necessary white light, which is broken down into blue, red and green wavelengths, but they have a tendency to emit a lot of heat and are more costly to use than fluorescent ones.
LED lights are energy efficient and low heat but their wave-length light varies so much from brand to brand that they can be complicated to use.
Specialised horticultural grow lights are purpose-designed, expensive and largely unavailable here.
Temperature and humidity levels are just as important as the actual lighting provision.
Room temperatures should average 18oC to 23oC all year round for houseplants to give their very best. This, with the help of a combination of fluorescent and incandescent tubes/bulbs, is not very difficult to achieve from late autumn through until early to mid spring. But summer, when the temperatures go off the scale, can be a major problem, especially as the majority of plants will not tolerate cold draughts from fans/air conditioning units.
Reasonable levels of humidity are important too: these levels can be maintained during dry weather by placing bowls/trays of water here and there amongst the plants. Overly dry atmosphere badly damages — even burns —leaves of many plant species.
If growing plants under artificial light doesn’t tempt you but you still want houseplants in shady rooms, African violets, Gloxinias and orchids are worth trying, as are a selection of foliage plants such as Sanseveria, Pothos, Philodendron and Dracaena, which can be moved around until they find ‘their’ place.
In addition, plants such as Parlour palm, Maidenhair fern, Bromeliad, Umbrella plant and the above mentioned Dracaena, Philodendron and Sanseveria will grow with very little light at all.
- Growing vegetables and herbs with artificial lighting needs a more complex technique and I will write about this at some point in the future.
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Published in Dawn, EOS, May 13th, 2018