can overkill lights harm a plant?

There is a point at which having more light won't be beneficial, and when a plant is very young is can be sensitive to too much light intensity. That said, you're completely fine.

Number of plants isn't really a variable to consider; this in particular deals with the grow space. You generally want 50w and 5000 lumens per square foot. When I have seedlings or a fresh clone under my 600w hps, I start the light 2' away and over a week work it to ~1' away - this ensures the plants are able to properly adjust to the light as such a rapid change would cause stress. A seedling or freshly rooted clone doesn't need that much light, either.

As for heat, use the back of your hand to get a good idea of how far to keep the light away. Warm is okay, but not hot.

 

No that will not harm your plants. I'm growing two under a 400 and it works fine. Just make sure you have at least 5 square feet of grow space for them. That light is actually a bit overkill for only 5 square feet so it may help to have up to 8 square feet for that light and two plants. A 2' x 4' area for that light and 2 plants would work great. Otherwise, its actually hard if not next to impossible to get too much light. At most, as you start nearing that 10,000 lumens per square foot, your amount of photosynthesis will start to taper off but it won't hurt your plants.

 

unless heat gets out of control, you're A-ok

 

I'm growing under two sixs. And my plants loooove it. If I were to grow one plant under the two lamps it would be a gigantic beast of a plant. The more light the better.

 

Nice!! I built a 2x2x4 for my 250, make sure you get an air cooled hood for that 400 in such a small space. Scrog or not, 3' of height leaves very little room for pots and light.

 

yea, the only problem you'll really have is heat issues.

one of my first grows, I was trying to grow in a little wardrobe cabinet that was like 4 feet by 3 feet by 6 feet and was using a 400 watt lamp. ended up being way too fucking hot and crisping some of my plants.

 

I'm using a 1000 in a 1m x 1m x 2m tent.

I've turned them & they started off great, but, now I have this shooting growth on the very tips of each cola.

It looks as though they are beginning to change back & keep growing.

However, the light cycle has remained the same.

The last two pics is what they looked like before they decided to stretch in this odd way.

You can see in pic 4 that the cola is nicely formed & then it just shoots up. BTW, these are Aurora Indica & THC Bomb

 

I have a tent that is the same size as the one you got. I have a 600 watt hps for mine though. A 1000 watt light is a little big for that, but it should work as long as you have a cool tube to keep things cool. You could probably dim that thing down to 75% if possible without noticing much difference.

 

Dim it?

I wish I could!!

I have a Solis Tek switchable ballast with inbuilt timer.

It can take a 1000, 600 & 400 at standard watts or can be boosted by an extra 50w. Unfortunately, I can't adjust it anymore than that.

The tent temp is no more than 28C.

I need to nut this out with what ever is wrong & before there is irreparable damage to my girls.

I forgot to mention that this stretching is only happening to the colas that are at a certain height. All colas at the same height are stretching.
Anything lower appears thick, frosty & normal.

 

Some of the digital ballasts are dimmable. I have a 400 watt iPower ballast which has a knob right on it. I can adjust it between 50%, 75%, and 100%. Right now I just started four plants in little cups so I don't need that much light. I have it dimmed at 50% for that reason to reduce my power consumption and light output since its not needed yet. They make 600 watt and 1000 ballasts which are dimmable also.

 

Yeah, but, I only just got this one & it cost me $440Aud. No globe!

Oh yeah, it is also remote control for the power, light globe adjustment & timer.

Anyone else got an idea?

Possible nutrient problem? I have no idea.

This sucks too, cause, I used to do this years ago with not one problem & for the past 3 yrs I've never completed a crop due to the plants dying at almost full flower! So gutted when that happens.

 

Are you talking Australian dollars? I'm in the US but I think that compares kind of close to our currency. I have a 600 watt MH/HPS with a cool tube which only costed me about 230 US dollars. Some can be more expensive though. I have no idea if they are better or what if they cost more.

What are you using for nutes and water? What kind of soil are you using? 28C seems to be close to 82F since we use Farenheight over here. I think the temps should be fine. Also, what kind of light are you using? An hps light will normally produce a yellow tint on your pictures and I don't see that.

 

Yes, Aud = Australian Dollars. Our $ is worth more than the US $ at the moment.

I'm using a Metal Halide globe (the one with the bubble of mercury inside). I'm about to go buy a new Hortilux 600w globe that is apparently more efficient than all others. Bah, marketing!

Nutes are good, as they are fresh & proper levels maintained. Water is ph optimised. Soil is coco peat & perlite mix.

 

I know that Australian dollars are worth more, but they are pretty close. It came to like a $20 difference at around $400 so thats pretty damn close.

Are you using Reverse Osmosis water? That is what I am using and it turns out that you need Cal-Mag with that. Beyond that, your problem could be the bulb. Your plants are flowering and you are still using MH. You need to switch to HPS once you start flowering. HPS can work for vegging and flowering, but Metal Halide can not. Its for vegging only. Get a high pressure sodium bulb and maybe that will fix your problem.

 

Hehehe, $20 could be my delivery fee!

I buy heaps of stuff from the US & it works out so much cheaper......for the things I buy.

I bought a globe today & it's very yellow compared to the other one.

It's also much cooler in the tent now too. 22C around 71F.

Almost forgot, our water comes from the mountains to a reservoir then pumped to a sub reservoir & treated with fluoride & chlorine & what ever other shit they use to make it 'clean'.

Our water is pretty good. Usually pH is 7.0 consistently.

 

There is such a thing as light bleaching, but you won't avoid it by adding more plants (which is the corollary to your question -- if a 400w might hurt 1-2 plants under it, would adding more plants prevent that? No.)

Has nothing to do with number of plants but the intensity of the light. Very difficult to get the intensity too high without having first raised the temps to the point that you burned your plants. In other words, too much heat is the problem way before too much light is.

To clarify, with HID you want a minimum of 50w per sq ft. Important clarifications, otherwise this advice will be snapped up quickly by newbies who then will advise others that 50w of CFLs is ideal, though clearly it is not. With HID you want 50-100w per foot, with CFLs double it.

 

Ummmm, what?

What are you trying to say?

You've lost me.

 

After the seedlings are a few inches tall, and entering the veg stage they should be ready for the 400w and grow nicely. I put my plants under HID lights usually by the 3rd-4th leaf set or when a rooted clone starts growing again.