Step 11: Lighting
What kinds of lighting are used for growing plants?
Most applications use HID (High Intensity Discharge) lights. All HID systems require both a ballast and a bulb in addition to the socket and reflector. You can also use a T5 High output fluorescent bulb which blends the light spectrum. You can use regular T12 fuorescent bulbs for smaller seedlings and cuttings.
There are two types of T5 bulbs -- one for blooming and one for growing. Compared to their HID counterparts, they use less heat and all of the spectrum output is used by the plant. The ballast works for both types of bulbs.
There are three main types of HID: Metal Halide(MH), Mercury Vapor, and High Pressure Sodium (HPS). For growing, only MH and HPS are used.
What do I need for HID?
If you're growing leaf/bushy plants (lettuce, greens, herbs) - you want MH all the time. For plants with a vegitative and bloom phase (i.e. tomato, flowering annuals, fruits) - you want to start with a MH and then swtich to HPS while the plant flowers and starts producing fruit. If all you're doing is supplementing natural light - use HPS.
What if I can only afford one light system?
Here are a few options
1. Use a MH system for growth and then an HPS conversion bulb for flowering.
2. Use HPS for flowering and a MH for growth
3.Buy a standard system and upgrade to an enhanced color corrected bulb. Most go for an HPS system because of the higher lumen output per watt compared to its MH counterpart.
4. Buy a switchable system where the ballast can support either type of bulb
5. Use a T5 system with cool spectrum lamps and warm spectrum for flowering.
What is this conversion bulb?
You can only match a bulb to its ballast (ie MH does not work on an HPS ballast). However, special conversion bulbs will work with the opposite type of ballast.
HID System Primary Supplement
2 lamp 2 foot||||||||||||||||||||||||1'X2'||||||||||||||||||||||||1'X2'
4 lamp 2 foot||||||||||||||||||||||||1'X2'||||||||||||||||||||||||2'X2'
2 lamp 4 foot||||||||||||||||||||||||1'X4'||||||||||||||||||||||||1'X4'
4 lamp 4 foot||||||||||||||||||||||||1'X4'||||||||||||||||||||||||2'X4'
8 lamp 4 foot||||||||||||||||||||||||2'X4'||||||||||||||||||||||||3'X4'
Reflector shape/size is also going to play a role -- and these are approx. measurements ;)
from m little supplier catalogue...
100watt HPS or MH: $170
400watt ranges from: $250-$350
400watt switchable: $290-$400
2 lamp 2': $125
4 lamp 2': $190
T5: 2' = $16ea 4'=$17ea
HID: $50(100watt MH) -- $35 (400watt MH) -- $30 (400 watt HPS)