LIGHTING

Light is critical to a plant's survival. Each plant requires a certain level and quality of light for proper growth. The easiest way to determine the amount of light a plant will receive in a specific location is to purchase a light meter. Each meter measures slightly differently. Read the directions carefully to determine how to interpret the information provided by your light meter. I use a meter that shows footcandles. Others may simply indicate "low," "medium," or "high." Low lighting is 1,000.1,500 footcandles. Medium light is 1,500.2,500 footcandles, and high lighting is 2,500 and higher footcandles. [A "footcandle" is the amount of light a candle gives off one foot from the flame.]

North Windows

Any window facing north normally provides semi.shade or shade conditions for plants growing directly on the windowsills. If there are trees, buildings, or even roof overhangs further limiting the light through the window, then classify it as a shaded situation. You may use shade preferring plants in any location where you have enough light to read even if it isn't directly on a windowsill or sitting on a table in front of the window.

East Windows

These windows receive direct sun only in the morning. This is a good location for flowering plants requiring low to medium light levels.

South windows

This is an excellent location for plants needing high light levels. Some plants may even burn if the window is not shaded with a sheer drapery or partially closed blinds. This location can be hot in the summer.

West windows

This window provides high light levels particularly in the afternoon. Shading may be required for some plants. This location can be excessively hot in the summer.

Overcoming Light Problems

Supplemental lights are the easiest way to overcome light problems. There are several types of lights available to the indoor gardener today. Light bulbs emit different wavelengths on the light spectrum. The light wave spectrum ranges from ultra violet to infrared (the orange and red end of the spectrum). The visible portion of the light spectrum is from violet to red. These are the colors that we can see. Plants may be harmed by ultra violet light that, fortunately, is screened out by most glass.

Plants need the full range of the visible light spectrum for successful photosynthesis. Photosynthesis is the process that turns carbon dioxide, water and light into the carbohydrates used by the plant. These carbohydrates are further processed into the various compounds needed by a plant for growth. The distance between the light and the plant determines the amount of light energy actually received by the plant. More light is received when the lights and plants are a short distance apart. You will prove this using your light meter.

What Light Bulbs are Available to the Indoor Gardener?

The three most commonly available lights for the indoor gardener are incandescent, fluorescent, and halogen. The advantages and disadvantages of each of these are discussed below./

Incandescent. These are the light bulbs we use in lamps and other lighting fixtures. Benefits: low cost. Disadvantages: high heat output, poor light quality (for growth purposes), low efficiency in using electricity, and short life span.

Fluorescent lights: Available as cool white or warm white bulbs. Be careful when buying these. Many are now only 25 watts instead of the old 40 watt tubes. Benefits: low cost, cool running, better balance of light, and longer life span. Disadvantages: light intensity decreases from the middle of bulb to ends of bulbs, may need to balance the available light spectrum by combining cool and warm light bulbs for flowering plants, and low efficiency in use of electricity.

Halogen Lights: These lights are rapidly becoming common in shoplight fixtures and lamps. They normally come in 150 and 300-watt bulbs. Benefits: readily available, provide pleasing white light similar to natural light, provide full light spectrum for plant growth, and they provide higher level of footcandles per unit of electricity used than other bulbs. Disadvantages: low efficiency in using electricity, medium life span of bulbs, and cost of bulbs.

Recommendation

I've experimented with different types of lighting systems. The majority of foliage plants grow well under my normal cool white shoplights. Sansevierias and cryptanthus fluorish under these lights. Others, such as my Lithops or Pelargoniums require a western facing windowsill to do well.

Is Your Plant Receiving Too Much or Too Little Light?

Signs of too little light: Plant just sits without showing any growth. Leaves may turn yellow or brown as the plant slowly dies. The plant drops lower leaves. Leaves are smaller than normal. Leaves are spread apart on the stems. Plants such as cacti or succulents may show very abnormal growth.

Signs of too much light: Leaves are pale yellow or have white spots from being bleached by the sun. They may simply dry up even though the soil is moist or they may curl away from the light source.

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