Plant Grow Lighting FAQs
Find answers to common indoor plant grow light questions below or click Grow Light to go directly to our professional quality Grow Light product offerings.
What do I need to get started?
Which type of grow light should I choose?
When should I use Metal Halide (MH) Plant Grow Lights? When should I use High Pressure Sodium (HPS) Plant Grow Lights?
When should I use Fluorescent Plant Grow Lights?
Light Bulb Questions? What is the difference between Standard and Enhanced Performance HPS Lamps?
What is the difference between Universal MH and Super Horizontal MH Lamps?
How often should I replace my lamp/light bulb?
What wattage grow light should I use? Should I use specialty lamps and do they work?
What reflector should I buy?
How many hours should I run my plant grow light?
Q
What do I need to get started? A
A grow light consists of a lamp, a socket assembly, a ballast, and a reflector. Choose MS, HPS, Dual MH/HPS or a Fluorescent Grow Light System depending on your needs. You can purchase a fully assembled grow light system or you can buy components to customize your grow light. You may also want to consider a Grow Light Lift, and/or a Light Mover to make your set up more efficient.
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 Q
When should I use a Metal Halide (MH) Plant Grow Light? A
Metal Halide (MH) lamps produce a balanced light spectrum closest to natural light. Plants can be grown from start to finish using metal halide plant grow lights. MH is the best type of light to be used as a primary light source if little or no natural sunlight is available. Metal Halide's balanced spectrum contains the common blue and red wavelengths needed for rapid foliage growth.
Metal Halide Grow Lights
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Q
When should I use High Pressure (HPS) Plant Grow Lights? A
High Pressure Sodium is 10-15% more energy efficient than Metal Halide light but does not have a balanced spectrum. HPS emits an orange/yellow light similar to the sun's spectrum in the mid day. HPS is best used as supplemental light and is particularly good at promoting flower growth.
HPS Grow Lights.
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Q
When should I use a Fluorescent Grow Light? A
Fluorescent Grow Lights are very energy efficient and run cool. Fluorescent Grow Lights are best for growing seedlings.
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 Q What is the difference between Standard and Enhanced Performance HPS Lamps?
A
Standard HPS lamps lack blue spectrum light. This can sometimes make a plant get too leggy during the vegetative growth stage. Enhanced Performance HPS lamps have a wider blue spectrum, which makes a significant difference in plant growth.
Enhanced Performance HPS Lamps
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Q What is the difference between Universal MH and Super Horizontal MH Lamps?
A
Super Horizontal MH Lamps provide 12% more light output than Universal MH Lamps, but must be burned in horizontal position.
Super Horizontal MH Lamps
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 Q
What wattage should I use? A
Optimum wattage depends on several factors including the size of the growing area and the type of plants. Plants that require more light (i.e. tomatoes), need a higher wattage system. MH systems come in 100, 175, 250, 400, 1000, 1100, and 1500 watts (250, 400, and 1000 watts most commonly used). HPS lamps are available in 100, 150, 250, 400, 430, 600, 1000 watts (250, 400, 430, 600, and 1000 watts most commonly used).
Use the charts
below as a general rule of thumb
when choosing which wattage you will need:
Area
Size
|
Use
|
| 2'
x 2' |
250W
& under |
|
4' x 4' |
400W and 600W |
| 8'
x 8' |
1000W |
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Q
How high above the tops of my plants should I hang my grow lights?
A
The higher the lamp wattage the hotter the lamp. Hang your grow light high enough so your plants don't burn. The size of the coverage area is another factor. For more light coverage, raise the light. The type of plants you are growing also determines the height. For plants requiring very intense light, keep the lights as close to the plants as possible. Use a Light Hanger to make it easy to adjust the heights of your grow light. You may also want to use a Light Mover to increase the area of light coverage.
|
Lamp
Type
|
Lumens
(light output)
|
Sq.
Ft
|
Area
|
Mounting
Height
(from top of plants)
|
| HPS
70W |
7,600 |
2
|
1'
X 1' |
1.5'
- 2'
|
| HPS
100W |
9,500 |
2
|
1'
X 1'
|
1.5'
- 2'
|
| MH
100W |
9,000 |
2
|
1'
X 1'
|
1.5'
- 2'
|
| HPS
150W |
16,000 |
1
- 4
|
1'
X 1'
2' X 2'
|
1.5'
- 2'
|
| MH
175W |
13,000 |
4
- 9
|
2'
X 2'
3'
X 3'
|
1.5'
- 2'
|
| HPS
250 |
28,500 |
4
- 9
|
2'
X 2'
3'
X 3'
|
1.5'
- 2'
|
| MH
250 |
22,000 |
4
- 9
|
2'
X 2'
3'
X 3'
|
1.5'
- 2'
|
| MH
400W |
36,000 |
16
- 36
|
4'
X 4'
6'
X 6'
|
2'
- 3'
|
| HPS
400W |
50,000 |
16
- 36
|
4'
X 4'
6'
X 6'
|
2'
- 3'
|
| HPS
1000W |
140,000 |
36- 100
|
6'
X 6'
10' X 10'
|
3'
- 5'
|
| MH
1000W |
110,000 |
36
- 100
|
6'
X 6'
10' X 10'
|
3'- 5'
|
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 Q
How long should I run my light?
A
Most plants do well with up to 12 hours of light a day. Long day plants may require up to 16 hours. For best results you may have to adjust the run length according to how your plants react. Use a timer.
Plug In Timers
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Q
How often should I replace my lamp/light bulb? A
HID lamps should be replaced before they burn out. HPS lamps should be replaced at least every 2 to 2 1/2 years. MH should be replaced at least once every year. Although lamps may look like they are fine you are not getting full lumen output when lamps get old. After one year (12-14 hours a day) of use, your MH lamp puts out around 65% to 70% of the initial lumen output. After 1 year most HPS lamps give about 85% to 90% of the initial light output.
Grow Light Bulbs
Note: It is impossible to see with the naked eye if a lamp is dimmer or has lost a good percent of its initial life.
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 Q
Should I use specialty lamps and do they work? A
If you can afford them, you should use them. Specialty grow lamps like the Eye Lighting's Hortilux and the SunMaster's Warm Deluxe are engineered for plant growth. Eye Lighting is the industry leader in HPS grow lamps and SunMaster is the industry leader in MH grow lamps. The "Hortilux" lamps offer up to 25% bluer light than a standard HPS. This boosts green vegetative growth, and builds stronger stems. The "Warm Deluxe" lamps offer up to 25% redder spectrum than standard MH lamps. This helps with flowering and fruiting in plants. Both lamps also provide more lumens than standard HID lamps.
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Q
What reflector should I buy?
A
Horizontal reflectors are the most common reflectors used for plant lighting. They do an excellent job concentrating the light in a downward direction, giving your plants a more intense coverage. The only disadvantage to horizontal hoods is the amount of heat that is directed downward. You can overcome the heat problem with fans, and blowers as long the reflector is "air-coolable".
Note: Glass is optional on most horizontal hoods, and is required on MH systems for UL listing.
Grow Light Reflectors
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