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Old March 16, 2009   #1
gflynn
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Default Metal Halide Lights and Hardening Off

Tomato Folk,

Right now I am using at 430 watt High Pressure Sodium light. These are Yellow Red light in the spectrum. They are good for seed starting.

Every year when I take my tomato plants outdoors the leaves burn at least a little if not a lot.

If I was to use the 1000 Watt Metal Halide (blue) light instead that my brother just loaned me would I avoid leaf burn when I took the plants outside?

Greg
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Old March 16, 2009   #2
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I was under the impression that HPS was more for the flowering/fruiting phase of the plant. I think you will find that the MH is better for seed starting than the HPS. Ami
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Old March 17, 2009   #3
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Ami,

The Metal Halide makes a Blue light much like the sun in mid-summer. Red/Yellow light is much more like what you will see near the beginning and end of the year when the sun rides lower in the sky. I have heard it said that the blue light is better for vegative growth and Red/Yellow is better for Flowering and Fruiting as you said, however, seeds start early in the season so I would assume they would have adapted to Red/Yellow Vs Blue.

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Old March 17, 2009   #4
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MH lights can go from 3,000 K to 20,000 K color temperature.

dcarch
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Old March 18, 2009   #5
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Dcharch,

What is color temperature?

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Old March 18, 2009   #6
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Quote:
Originally Posted by gflynn View Post
Dcharch,

What is color temperature?

Greg
Here you go:
http://en.wikipedia.org/wiki/Color_temperature

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Old March 18, 2009   #7
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I dunno why you feel you need HID lighting for seed starting. Its just alot of juice and the lights are too hot to get close to the seedlings where they need to be...Also I've read about T5 lighting. In my opinion and what I've found in growing my own is that the T8's are working just fine. In my four foot T12's right now I have a 6500K daylight and a cool lamp that is in the 2700-3000k range...I know you don't get the lumens out of these bulbs but seedlings don't need it. I'd go with fluorescents unless for some reason you're doing a total indoor grow.

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Old March 18, 2009   #8
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This year I have two fluorescent shop lights which I kept touching the leaves the whole time(plus constant fan directly on the plants, and I have the healthiest transplants ever before. These are in 1gallon pots and just moved outside at nearly a foot tall with beautiful broad leaves and tight internodes. Back in the day I used the big HOT metal halides and HPS for other things, and even then you don't need something so strong unless you plan on growing full size plants.
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Old March 19, 2009   #9
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Vince and All,

This year I am starting 500 tomatoes and 70 peppers and a bunch of Petunia's. They are currently all together and will need to be separated. They take up an area of about 6 feet by 2.5 feet. I have a motorized track that pushes the 430Watt HPS light back and forth. I am keeping it on 100% of the time.

Very soon I will need to start putting the plants in 18oz plastic beer cups. I usually start later and I can just sit'm out on the deck and on top of the camper around April 1st or later. As is I will need to start converting some to cups soon!

My brother gave me a 1000 watt MH lamp and I am wondering if I should switch up so I can cover more area? I am worried; however, that switching will burn the plants. Also, I wonder if the MH light will reduce burn when I finally put them outside 2 to 3 weeks from now.

Greg

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Old March 24, 2009   #10
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That is a good idea to have the motorized track.

I don't have a problem with leaf burn. Just set the plants under a tree that will give them partial sunlight, for maybe 3 days. Then throw them into full light, and no burn. This works for me.
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Old March 24, 2009   #11
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Vince,

The tree idea is not a bad one. Perhaps the branches swaying prevents continous sun and keeps the plants cooler? I am a little worried about bunnies and deer, however.

I wonder if your flouresent lights are key to you avoiding burn? They have a component of green light.

The track is nice because it keeps the plants a little cooler. Also, I borrowed the setup so its free :-)

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Old March 26, 2009   #12
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Flourescent lights do not help avoid sunburn when planting out.
If anything, they need to be hardened off even more than if they
were grown under bright metal halides.

You can put them up close against the north side of a building
for a few days (protected from beasts, slugs, etc). The sun is still
to the south at this time of year, so that should be ok, although
a few cloudy days is better.

If the sun is shining, one usually needs to build up gradually
to a full day in the sun (like all shade the first day, hour of
sun the next day, then few hours, and so on).

I have not gone from metal halide to direct outdoor sunlight,
so I don't know how much that changes the time that they
need to adapt. They need to adapt to wind, too, so I start
with a couple of hours in the shade outside, and build up to
a full day gradually, with more and more sun each day if the
weather is actually clear and sunny. (If it is cloudy the whole
time, no big deal. After a week of cloud filtered sunlight, they
can handle direct sun without problems, assuming that they
have enough roots to stay hydrated.)
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Old March 28, 2009   #13
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Right now I have my seedlings under a light fixture containing 3ea 48" Vita-Lite Power Twists with a CRI of 91 and 6ea 26W CFL's running at 6400K. Just got done building my racks mounted on a board with rollers on the bottom. Each rack has 5 shelves that I put my newly potted plants on and put in my south facing Window. Being on rollers I can turn them 180 degrees every day so they get even lighting. Here's a couple pictures of my racks from last year. When planting out time comes along they are ready for whatever mother natures throws at them. Ami
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Old March 30, 2009   #14
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Things are warming up around here so I am starting to think about putting the plants outdoors.

Here comes the burn!

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Old April 13, 2009   #15
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Quote:
Originally Posted by mx4inpa View Post
Plants reflect green light. It's also what lumens are measured in, because thats what our eyes see best. Pretty much all bulbs have that component.

If you want what I consider to be the best bulb then youd go ceramic metal halide. They have a CRI over 90 and the most sun-like spectrum of any bulb on the market. Lots of money for a 1k though (around $200). You can get 400w retrofit CMH that will run in a HPS ballast for around $50.
This is what I am using in my growroom. the CMH is the best way to go.
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