Welcome to ProgressiveGardening.org
View Indoor Gardening In A Bright New Light!
Has weather ever dampened your gardening enthusiasm? Too hot or too cold? Too humid or too dry? Too much rain, or not enough? Have you ever wished or imagined being able to garden in the air-conditioned comfort of your home? Now you can even grow vine-ripe tomatoes indoors, all year long with high intensity garden lighting!
Advancements in artificial lighting technologies over the past decade have introduced a whole new generation of plant growing lights for the indoor seed starter, gardener, and houseplants enthusiast that are brighter, more efficient, and better looking than ever. Now it is possible to remove the weather aspect of gardening forever, by bringing the garden into the climate controlled comfort of your home.
Below you will find easy-to-understand information on the various artificial light sources used in horticultural applications along with some of the more important factors to consider when choosing from among the many different indoor and greenhouse plant growing lights that are available today.
General Lighting Requirements For Plants
To determine how much light a plant will require, consider where and how it grows best in its natural environment. Most vegetables, for instance, grow best in full sunlight, which means as much light as possible must be supplied to grow vegetables indoors. Foliage houseplants like the Philodendron grow in full shade and therefore can grow normally with relatively little artificial light. Exotic plants, such as Bromeliads and Orchids, grow in varying conditions depending on the species. Some grow in deep shade in the jungle, while others grow in bright sunlight. The lighting level required for growth indoors depends upon the characteristics of the particular plant being grown.
Plants NEED Darkness
Plants need dark periods. Periods of light (called photo-periods) and dark periods and their relative lengths have an effect on plant maturity. Recent studies have conclusively proven that it is not just the length of the day which affects growth, but the duration of the dark period which follows. The dark period of each day affects flowering and seeding of most plants. Although many plants can grow under continuous light, nearly all plants prefer a dark period each day for normal growth. All plants need some darkness to grow well or to trigger flowering. The ideal photoperiods of plants vary, some preferring long days and short nights; others the reverse; and some do best when the length of the night and day periods are equal.
Color Temperature
In scientific terms, Kelvin temperature is a measure of the color of a light source relative to a black body at a particular temperature expressed in degrees Kelvin (°K). In simpler terms, it is the degree of warmth or coolness of a light source, not with regards to the physical temperature, rather to the visual temperature of the light. The higher the degree K, the more blue, or "cooler" the lamp appears. The lower the degree K, the more "warm", or red the light appears. Incandescent lights have a low color temperature (approximately 2700°K) and have a red-yellowish tone; natural daylight Kelvin Temperature Chart with Lighting Examples has a high color temperature (approximately 6000°K) and appears bluish. Today, the phosphors used in fluorescent and high intensity (HID) lights can be blended to provide any desired color temperature in the range from 2800°K to 6000°K.
Color Rendering Index (CRI)
The Color Rendering Index (CRI) is a rating scale for light sources (lamps) from 0 to 100 to indicate how accurately colors can be perceived under a light source. The higher the CRI, the more accurately colors appear. Technically, CRI ratings should only be compared for lamps with similar color temperatures (Kelvin ratings).
Lumen Output
Most grow lights are rated for brightness according to their lumen output, which is a measure of the perceived power of light by humans. Some manufacturers are marketing indoor plant grow lights using a term known as PAR watts, or Photosynthetically Active Radiation, which is claimed to directly indicate how much light energy is available for plants to use specifically in photosynthesis. Generally speaking, higher lumen or PAR watt values are better for indoor plant growth.
Click here to read more about specific types of plant grow lights.
