Growing Under Lights
How to Grow Seeds and Plants Under Artificial Light
NOTE: The products linked to on this page are supplied by our
partner, Gardener's Supply, you may order there with confidence.
The benefits of growing under lights are hard to ignore. There is simply no
better way to grow an abundance of stocky green seedlings. If you grow
flowering plants indoors, such as orchids, African violets, citrus and
hibiscus, lights will keep them blooming almost year-round. If you want a
wintertime harvest of vine-ripened tomatoes, herbs and salad greens, that
too can be accomplished with lights.
It's easy to grow plants under lights when you have a system that provides
adequate light. This
has color-balanced bulbs that promote growth.
By learning how plants use light and about the many bulb and fixture options
on the market, you can select an indoor lighting system that is perfectly
suited to your home and the types of plants you want to grow. Not all plants
require the same color, intensity and duration of light. Read on to learn
about your options.
The Right Color
Sunlight contains the complete spectrum of light including all colors of
the rainbow: red through yellow to blue and violet. Plants use the full
spectrum for photosynthesis, although red and blue light seem to be most
critical. Red light stimulates vegetative growth and flowering, but if a
plant gets too much red light, it will become tall and spindly. Blue light
regulates plant growth, which makes it ideal for growing foliage plants and
short, stocky seedlings.
Some plants perform best when given more of a certain color light. An African
violet will thrive under blue light, but if it doesn't receive an abundance
of red light, it may never flower. If you learn what color light your plants
need, you can then select the right type of bulbs to meet that need.
Rotate your plants each week. The light from a fluorescent bulb is more
intense at the center of the bulb than it is at the ends.
Paint your growing trays white, or use foil-covered reflectors to increase the amount of light your plants receive.
Replace fluorescent tubes when the ends darken. That means the tube is old and the light output may be less than half of a new bulb.
Clean your fluorescent bulbs each month. Dust and dirt can dramatically decrease the amount of light emitted.
Place your hand where the light hits the foliage. If you feel any warmth, the light is too close.
The Right Intensity
The intensity of light that a plant receives isdetermined by the wattage of
the bulb and by how close the plant is to the light source. Just as plants
differ in their need for certain colors of light, they also differ in their
need for light intensity. Typically, those plants that are native to tropical
jungles or shady forests do not require as much light as plants that evolved
in dry, sunny climates such as the Mediterranean or southern Mexico.
Most flowering houseplants, like African violets and begonias, are happy
being 10 to 12 inches away from a light source. Non-flowering, like ivy
or philodendron, plants can be placed as much as 36 inches away from a
light source. But many flowering plants, such as orchids, gardenias and
citrus, as well as most vegetable plants, require a much higher light
intensity to flower and produce fruit.
The Right Duration
No matter what types of plants you are growing indoors, you must be sure to
always give them a rest. When it's dark, plants respirate, which is an
important part of their growth process. The balance of rest time to active
growth time affects many biological processes, including the growth rate,
and the setting of buds and fruit.
Botanists usually divide plants into three categories relating to their
preferred day length: short-day, long-day or day-neutral. Short-day plants,
such as chrysanthemums, kalanchoe, azaleas and begonias, will thrive on less
than 12 hours of light per day. In fact, these plants must usually go through
a series of even shorter days before they will set buds and flower.
Long-day plants require at least 14 to 18 hours of light each day. Most
vegetables and garden flowers are long-day plants, and when they don't
receive enough light they get pale and leggy. Day-neutral plants, including
foliage plants, geraniums, coleus and African violets, are usually satisfied
with 8 to 12 hours of light all year-round.
Types of Bulbs
You can choose between incandescent, fluorescent and high-intensity
discharge (HID) bulbs, each of which has its own benefits. Your choice
should be determined by the type of plants you want to grow, and where you
plan to locate your indoor garden.
INCANDESCENT BULBS are the type of light bulbs used in most homes.
They are a good source of red light, but a poor source of blue. These bulbs
also produce a good deal of heat in relation to the amount of light they
give off. If you position your plants too close to the bulb, the foliage
can be easily burned. Halogen light bulbs produce even more heat and will
easily scorch foliage.
produce two to three times more light than incandescent bulbs for the same
amount of energy. They are the most inexpensive lights for indoor gardening.
The color of light produced is determined by the phosphor coating on the
inside of the bulb. Cool white bulbs are a good source of blue and
yellow-green light, but are a poor source of red light. They are used for
interior lighting in schools and office buildings, and are the most commonly
available type of fluorescent bulb. Plants grown under cool white bulbs
will be stocky or even slightly stunted. Warm white bulbs emit plenty
of orange and red light, but less light in the blue and green spectrum.
If you are growing seedlings under 2-bulb fluorescent fixtures, you can
usually achieve a good color balance by combining one cool white and one
warm white bulb.
Full-spectrum fluorescent bulbs, such as our new
T-8 SunLite Bulbs,
are 20 percent more efficient than conventional grow lights. They last 4,000
hours longer, and perform better over time. Even after burning for 10,000
hours, they retain 95 percent of their original light output. They also
contain less mercury; that's good news for the environment. And SunLite T-8
bulbs use quiet electronic ballasts -- no annoying buzz.
HIGH-INTENSITY DISCHARGE LAMPS
are used by commercial growers and serious horticulturalists. They generally
emit twice the amount of light (lumens) as an incandescent or fluorescent
bulb for the same amount of energy. Because they are so energy-efficient,
HIDs are used to light shopping malls, baseball fields, streets and gymnasiums.
The special fixtures and bulbs used in HID lighting are considerably more
expensive than those needed for incandescent or fluorescent lights. They also
tend to be high-wattage bulbs, so you need to consider the load on your
electrical system. Some of these lights burn so brightly that they must
be located in a special room and eye protection must be worn when working
Metal halide, high-pressure sodium and mercury vapor lights
are all HIDs. Metal halide lights emit an intense, bluish-white light that
is excellent for growing plants. The foliage stays green and vigorous, and
plants are usually stocky and strong. At present metal-halide are the number
one choice for serious indoor gardeners.
Mercury vapor lamps emit an intense bluish light. These lamps produce
a relatively well-balanced, high-intensity light. High-pressure sodium bulbs
are usually used to promote flowering and fruiting. Their yellow-orange hue
makes plants think that fall is coming, which stimulates flower and fruit
production. When used exclusively, high-pressure sodium lights produce
leggy, weak-stemmed plants.
Whether you grow under lights for only a few short weeks each spring, or
make it a year-round hobby, today's technology makes it easy to ensure
that your plants get the quality, intensity and duration of light they
need to stay in peak condition.
If you have any questions, contact us!