Metal halides?

[tmmason10]

Hey all,

I have been doing a good amount of research and also have asked about this topic on other forums, and I want to pick the minds of the nuthouse. I am looking to give my tropicals some pep and get a good indoor setup going. I originally was going flourescent but I am now heavily leaning towards metal halide. Any one have any experience with MH and would you recommend it?

 

[lupe21]

metal halide produce a lot of heat, good ventilation is required

 

[monza]

They are the old standard 'grow' light. New tech is steering towards high output t5's. Cheaper, less power consumption and as stated above way less heat.

 

[Redwood Ryan]

I agree that they're pretty expensive (to buy and run) and very hot. I think you may be overthinking this a bit too much Tom . The trees will do well under T5s.

 

[tmmason10]

I agree that they're pretty expensive (to buy and run) and very hot. I think you may be overthinking this a bit too much Tom . The trees will do well under T5s.

Ha yup, pretty sure I am overthinking it. Just want to be sure.

 

[tmmason10]

If I had the money, I'd buy both and run tests because there is a lot of debate with very little side by side growth comparisons.

 

[edprocoat]

Well, maybe, well done bonsai trees would be nice....

ed

 

[tmmason10]

Well, maybe, well done bonsai trees would be nice....

ed

Well that would be the goal, agreed.

 

[FrankP999]

I use T5-HO and have two 4 foot fixtures with 4 bulbs each. That is a total of 432 watts at 54 watts per bulb. The bulbs last me about 2 years but I do not use them in the late spring or summer as everything goes outside then. My ficus like it as do my orchids. My grow area is 2'x4'. I have to keep low light orchids at the edges or they burn. I have some 4 inch cuttings of Green Island Ficus that have tiny figs starting to form.

I started slowly with a single T5-HO for about $150 and added a second one this year.

 

[Bonsai Nut]

I have a LOT of experience with metal halides.

Where to start... first you need to make sure you are buying the proper bulbs. You don't want to get just any old bulb from Home Depot to grow plants. You are interested in bulbs that maximize "Photosynthetically Available Radiation" or "PAR" for short. In a nutshell, chlorophyll A and B absorb light in two narrow bands, peaking at about 440nm (violet/blue) and 670 nm (orange/red). You want bulbs that maximize light in this spectra - light in other bands is useless to your plants.

MH bulbs that maximize PAR can be bought from horticultural supply centers, or aquarium supply houses. Unfortunately all MH bulbs degrade rather quickly with use. You will lose 50% of their spectral intensity in approx 6-9 months of 10 hour per day use. That may be ok for you - just start each winter with new bulbs and toss the old ones in the spring when you move your trees outside.

Another consideration to take into account is distance from fixture to plant. As people have pointed out, metal halides are HOT. They generate a fair amount of infrared radiation, making them great heat lamps However your plants will not appreciate being within 24" of the bulb. Light diminishes based on the square of the distance from the source, so as you double the distance, you actually reduce the light by 75% (i.e. the plant receives only 1/4 as much light). You may find that you are better off buying one high wattage bulb (say 400 watts) and using it several feet above your plants, than you are trying to create an array of lower wattage bulbs.

Finally, metal halide is a point light source, so you need to be concerned about shadowing. If you leave your plants unmoving, and the light unmoving, you will find that your trees all grow toward the light, and any branches that are in shadow will wither and may die. You need to rotate your trees, or (as in many greenhouses) buy a motorized light rail to move your light slowly back and forth (eliminating shadows).

If you need any other info, ask away. I didn't want to write too much at one go...

 

[woodguy]

I use a metal halide for my tropicals and orchids during the winter. Results have been very good. Orchids stay off to the edges and plants that will tolerate higher light stay in the center under the bulb. As BNut pointed out you do need to turn and move stuff from time to time get even light exposure.

 

[tmmason10]

Great informative post bnut, a lot to take in. Thanks for sharing woodcut as well. I am going to try and stop by a local hydroponics store today and check some of thr stuff out in person.

 

[tmmason10]

I went to my local hydroponic store today and went with this fixture. He recommended it over metal halide for all the reasons you have stated. I'll post some pics at some point but thank you all for your input. I'll update this with some progression shots of growth too. Had to get a light today I might have already lost some of my tropical starters as they were in thr cold dry window sill.

http://www.hydrofarm.com/pb_detail.php?itemid=10658

 

[tmmason10]

So here is a picture of my setup for now. I plan on enclosing the whole rack with 4mil contractors poly sheeting to keep it humid.View attachment 19184

 

[Fangorn]

I have a LOT of experience with metal halides.

If you need any other info, ask away. I didn't want to write too much at one go...

Hey Bnut I do have a question or two.
I've been using a 400 watt MH in my basement (during the winter) for a few tropical trees and assorted house plants. The bulb is about 18-22" above trees and while they've been doing OK, they never really thrive. I've always assumed that it was because they are in a chilly basement, but could it be because they are too close? I've measured the temp at the tallest tree and it was about 76 degrees
I'm also currently using a green blub, would I be better off with a different color?

 

[Bonsai Nut]

Hey Bnut I do have a question or two.
I've been using a 400 watt MH in my basement (during the winter) for a few tropical trees and assorted house plants. The bulb is about 18-22" above trees and while they've been doing OK, they never really thrive. I've always assumed that it was because they are in a chilly basement, but could it be because they are too close? I've measured the temp at the tallest tree and it was about 76 degrees
I'm also currently using a green blub, would I be better off with a different color?

Other people keeping tropicals can chime in, but at least for me, my tropicals take a rest during the winter (they stay outside year round in Southern California). It gets cold at night (high 40's - low 50's), but the days are all temperate in the 60's or even 70's. They stop growing from Sept-Oct and perk up again in January-February. This holds true for tropicals planted in my landscape (ficus, etc). So I guess what I am trying to say is it may not be normal to expect strong growth in an artificial lighting setting if you are only overwintering your trees because your trees may think it's winter (but people's experience may be different depending where they live).

Grow lights that maximize PAR will have a bluish/red or purplish hue to them (because they are generating purple/blue and red light). Green light is generally NOT good for plants - the reason plants look green is they are reflecting all green spectrum lighting. If you are using a single-ended bulb, I would recommend something like this.
Also consider getting a good quality reflector if you don't have one. It will literally double your light output if you aren't currently using a reflector, or using a poor one. You may find once you change your bulb your grow picks up dramatically and my earlier comments no longer apply

 

[Klytus]

I recognise that shelving,i had something similar with 5 or 6 foot long mixed spectra fluorescent growing tubes.

I used it for gaining a few months whilst starting Brugmansia and Cactus.
It was in the window of my second floor flat emitting this strange pink light during the day.

I seem to remember various alien races breezing by these shelves in 90's space station sitcom Babylon 5,it may have been the methane breather,i don't remember.

 

[Kevster]

I have been reading a lot of people's indoor light setups and I see a lot of people have great advise. I moved all my tropicals inside my old 125 gal fish tank since its not being used and am using the HO compact florescent light strip I originally had on the tank which is 6 feet long and has 9 96watt bulbs in it of which there are many to
Buy and choose from. Currently I have 3 Actinic (put out only 420nm), 3 50/50 (which is 7,000k and actinic) and 3 10,000k bulbs.

I'm sure it's overkill but the plants love it.
I just wonder why people don't look into the HO compact florescents?

 

[rockm]

"local hydroponic store"

Duuuude, you got a local headshop? Wow... The local Po-Po keep an eye on those down here. If you walk out with light fixtures, they will follow you home with a FLIR camera to examine your home for a grow operation...

Another source for halide fixtures is the aquarium supply store. Look in the reef tanks. No, not the "reefer" tanks...

 

[tmmason10]

I have been reading a lot of people's indoor light setups and I see a lot of people have great advise. I moved all my tropicals inside my old 125 gal fish tank since its not being used and am using the HO compact florescent light strip I originally had on the tank which is 6 feet long and has 9 96watt bulbs in it of which there are many to
Buy and choose from. Currently I have 3 Actinic (put out only 420nm), 3 50/50 (which is 7,000k and actinic) and 3 10,000k bulbs.

I'm sure it's overkill but the plants love it.
I just wonder why people don't look into the HO compact florescents?

That has been the general consensus I have noticed actually, people are suggesting t5hos and this is why o hanged my mind. I guess I'll keep this updated with progress and results