DISCUSSION THREAD. MH bulbs are 4200k. Are they a waste of time?

[wes2wright]

So i am a beginer grower. But in my instense studying i been doing to improve my skills (pity i wasnt this motivated at school) i have learned about light spectrums.

The optimal spectrum is between 5500k and 6500k. So i looked at my MH which i have such good things about and it is 4200k. This has left me confused. Is it cfls are better for light spectrum but lack in light penetration and vice versa?

I have read many threads on this and threads on MH vs Cfls but obviously we get a persons personal opinion. No doubt thats all we can give.

I am wanting to do the best growing i can and wish to gain some more knowledge so hoping everyone can give me any experiences they have using both. Or even better if someone has a few facts to explain this.

 

[woodydude]

Here's my take on the debate. Both MH and CFL's can offer something to the grower. Which you choose comes down to how much space you are wanting to illuminate and how large you intend to veg your plants. MH are more efficient, provide more lumens and run cooler per W than CFL's. Both can encourage stretch if the spectrum is not right. IMHO, T5HO are the best option for veg unless you intend to grow your plants larget than 2ft before flipping. Over 2ft, T5's loose their penetration. How much space, how large will you veg? Answer these to find the best option. JMO W

 

[bamfrivet]

the great thing about CFL is that they can be used in almost every grow situation to add a little bit of extra light with out adding a ton of heat and fit in small spaces. You can add CFL bulbs down between plants to get a little extra light to the lower buds and inner growth. If you tried that with a MH you would burn your plants up pretty good. CFL also cost less and keeps your electric bill down.

but mh are really only used for veg, not for flowering. you need different light spectrums for each stage of the plants life.

edit:
Also, t5ho are great for vegging, but the light dies off well before 2ft. floros light dies off drastically after about 4-6 inches. keep your t5's 2ft away from your plant and you'll get a tall plant really quick, but you'll have to stake it up through the whole grow.

 

[poindexterous]

4200K is entirely fine for vegetative growth, most Metal Halides are 4000K or so, some higher, but most are about 4000K. I have friends who veg and keep mother plants under HPS's which are 2100K and they even do fine, though I wouldn't use HPS for veg. I use 6500K florescent T-8's for moms and cuttings but switch to a 4000k MH for aggressive vegging and the lumen increase seems more relevant than the spectrum. The T-8's have to be much closer to the plants than a 1000watt MH of course.

 

[wes2wright]

I understand that cfls are useful for small spaces and saving electricity. But that aside just curious to which is more efficient? It seems that fluorescents are more effective and only failing when it comes to light penetration.

Poindexterous you said something interesting that the increase in lumens seems to outweigh the spectrum. I wonder if i had 2 2' plants with same lumens on the plant which would be more effective. The MH or the fluorescents

 

[poindexterous]

Hey Wes, the growth under my fluorescents is always just as nice as under my 1000watt MH as long as the foliage is within a foot of the tubes, farther and they'll stretch and get lanky, where the MH supports the same growth from four feet away. To me each is most appropriate and has it's place in very different situations. Small plants close together are most efficient under fluorescents, but when I want to veg them to two foot wide bushes in three gallon pots then fluorescents would be futile, and it's time for that 1000watt MH. Both MH and fluorescents are similar in lumens per watt at about 100 to 120. Each just serves a very different role for me, fluorescents for keeping moms, taking cuttings, and small plants in veg. MH and HPS for production. Hope that helps.

 

[wes2wright]

Thanks for that info. Helps a lot. Was a bit confused with it all and which way to go with the lights

 

[PacNW]

Ceramic metal Halide will improve that spectrum but, needs to be matched to the right ballast. T5ho with 4000k bulbs were anemic compared to 6500k. Woody is right. T5ho can be kept an inch from plants with a fan on em. This keeps the lumens real close to MH that are 16 inches above. Less heat and won't burn the grow.

 

[minorfelony]

4200K is a measure of the color spectrum that the bulb will output the most. Ideally, before anything was legal there was less choices and you either went with a 5-6000k bulb for Veg and a lower 2000k bulk for flower/bloom. Now, they have conversion bulbs and bulbs in between at 4,000k, 7,000k and 10,000k. Ideally I am understanding that the best bet is to go with a conversion bulb. (Quite expensive and haven't used one) This covers the whole spectrum and emits light in all the ranges listed above. (with no peaks and with no pointless peaks in the green or purples which the plants don't even use. This enables you to use one bulb from start to finish. A 4200k bulb would be used in a transition between flower and bloom bulbs if u want to mimic a summer in the N. Hemisphere. It will also work well for Veg.

 

[minorfelony]

I have used stategically placed CFL bulbs on lower branches. They did nothing but create heat burn. Nothing noticeable on the plant. Only more wires to deal with. I feel The lower branches are better off clipped and cloned. Let the plant finish to bloom. Cut off the top cola and the mid level(if u want). Continue to let the plant grow. There are pros and cons to this, I admit. It works though. This was the only way I could get the lower branches to produce anything big enough worth saving.