lighting for seedlings

[greentoe]

Next grow season I'm thinking of starting my seedlings under lights before I move them outdoors once they're around 4-6 weeks old or until they've outgrown their indoor space. I plan on creating a mylar covered enclosure with the top NOT completely covered so air can move freely in/out, the dimensions will be 57cm x 100cm and 120cm tall, the room the enclosure will be in is large and cool but is not well ventilated with fresh air.

 

I plan on filling the enclosure with 10+ seedlings and using a 12/12 light cycle, I have access to 80 W and 24 W CFL lights (both 6400K), which are more appropriate considering they're for seedlings and the small dimensions of the enclosure? and how many lights will I need?

Also will it be necessary to add a fan to reduce heat and increase oxygen or will having the enclosure not completely covered be OK? 

 

As the enclosure will only be used for a small amount of time I'm looking for a relatively inexpensive solution. I'm very inexperienced with lights and eager to learn more so any suggestions on different types (LED, T5, HID etc) is more than welcome.

 

Thanks in advance,

Greentoe

Edited May 11, 2014 by greentoe

[KRON BOURKE]

Ok so id add a small desk fan or something to move the air around, 80w cfl will do you fine. As for lighting schedule, 12/12 is a flowering cycle so go with 18 on and 6 off to replicate a long summers day and good luck to ya! Edited May 11, 2014 by KRON BOURKE

[greentoe]

Thanks, will do.
Because I'm transferring them outside after around 4 weeks I can only use a 12/12 cycle as it needs to match the natural cycle of the sun for when I transfer outdoors (will be transferring early October). If I start at 18/6 they will start to flower when transferred. The 12/12 cycle when indoors shouldn't make the plants flower because there is no reduction in the light cycle, plus I don't think a plant can begin to flower until it reaches sexual maturity (?).

 

Any idea how many 80W CFL's will be necessary?

Edited May 11, 2014 by greentoe

[wurlie]

yea a couple o 80watters be ok

to start @ 12hr and increase 15 mins each week for 4 wks and then outside Oct.

reduces chances of flowering onset

[KRON BOURKE]

my bad, been doin it wrong all this time! Why people get on here when they already know all the answers or are unwilling to take the advice they asked for in the 1st place is beyond me.

[greentoe]

Sorry Kron, didn't mean to sound blunt or unwilling to take advice, I was just stating the advice I was given in another thread which is why I was focusing my questions on types and numbers of lights required rather than light cycles. I do appreciate your advice, I just thought you may have misinterpreted my intentions to move the seedling outdoors. I tried to indicate some uncertainty on my behalf and hint at a request for further discussion with the question mark in brackets at the end of my last statement, I should have been more direct though. So do you disagree with wurlie's advice? If so why?

 

Big thanks to Wurlie for helping again too.

Edited May 12, 2014 by greentoe

[merl1n]

If you put any plant under a 12/12 light regime and it will go to head, if you put a seedling under 12/12 it will automatically turn to a flowering cycle. You need to grow the plant first, develop some branches for the buds to grow on. The more branches the more tips the more tips the more buds.

As you were advised by Kron you want 18/6 to grow the plant. You DO NOT need to match the light cycle, but if you place a plant outdoors when the natural light cycle is 12/12, the plant will stop its grow cycle (making branches) and convert to flower cycle.

Wurlie's advice is not starting until September then advance your lighting from 12/12 before putting outside. Using his method you'd be at 14/10 before going outside. Again not 12/12.

12/12 is for flower. 18/6 is for grow. These are hours that the light is on, 18 on and 6 off. So 12/12 IS a reduction in light, this causes flowering.

If you are starting indoor, you want 18/6 but, Personally I wouldn't be putting outside till mid to end of October. If you started now and kept the plant in veg, by the end of October your plant would be HUGE. You'd be able to do an indoor crop in that time

You say you've got advice from elsewhere, I'd say that info is incorrect. Maybe you need to verify your sources and confirm the information you receive.

 

Merl1n

Edited May 12, 2014 by merl1n

[Sir PsychoHashy]

Kron and Merl1n's info is correct.  However there is something to be said for being closer to the light cycle you will be putting them out into.

 

I have had issues with taking plants outside after being under 18/6 when it was about 13.5 hrs of daylight, and ended up having to assume that the sudden drop in light hrs was enough to trip the hormonal response in the plants as they had already reached sexual maturity before going out.  As a result I would now err towards going with 14-15hrs light per day to veg up for going outside, and make sure that the outside light cycle was at least close to this before going out.

 

If you start on 12/12 they will all start going into flower at sexual maturity, and the amount of light hrs outdoors will struggle to switch them back into veg.

 

Good luck with your grow, hope you post a grow diary for us to enjoy

[greentoe]

Thanks for the info, just going to clarify a few things to make sure there's no confusion. My purpose for putting seedlings under lights for 4-6 weeks (6 weeks is probably maximum due to limited space, dimensions in first post) at the beginning of their life is to be able to start the outdoor grow season a bit earlier and to have much healthier and mature plants by the time I transfer into the ground. I'll then continue veg outdoors until flower time next year, I do NOT want to induce any flowering until next year. 

 

Correct me if I've misunderstood your points:

• I can't start at 12/12 to match the sun's cycle, this will cause flowering even at a young age
• I can't start at 18/6 and transfer in October because the sudden drop in light hours when transferred outside will cause flowering
• 18/6 to 13.5 or even 14 hours of daylight may cause flowering also
• So 14/10 and then transferring outdoors to matching daylight hours in November is probably the only way to go?

Last year for my outdoor grow I germinated at the start of September (around 11.5 hours of light per day) and from that point on they were outside in pots, they were put in the ground 6 weeks later in mid October (13 hours of light per day). Even though the plants were sexually mature and getting only 12-13 hours of light they continued to veg. Was I just lucky then?

[merl1n]

OK, look I have a bit of a problem with your repeated reference to 'sexually mature'. When you change the lights, no matter how old the plants are, they will show their sex. For instance, I do this purposely so I'm not raising a male plant. I grow the plant probably till its on its 4th set of leaves then place the plant under a 12/12 light. By doing this the plant will show hairs or balls. If the seedling shows balls I rip it out, its a male. If it shows hairs its a female and is returned to an 18/6 light timing. Then let her grow to the desired size before going 12/12 for around 12-13 weeks. When you go 12/12 and leave her at 12/12, the plant has a huge growth spurt, so don't be filling the whole growing room with veg growth or you will run out of room for the buds to develop.

 

Merl1n