Grow light distance according to lux or wattage

[c4ctim4n]

Hello
I have started to plant some cactus seeds. I can't use sunlight so I have to use a grow light. I bought a 10 w COB LED chip. I have searched the websites a lot but there was no specific article about the distance from light to plants according to lux or wattage. there is just some general advice like 20 to 30 cm!

I have a lux meter app on my phone and I know this is not accurate but this is the only option I have. at 30 cm away it shows 1000 to 1500 lux that is too low for plants. So I have this question: is the effect of lux equal for colored light(growing led) and white or sunlight? I mean if the lux of sunlight 5000 be OK for my plants, is this correct for artificial light too? Because grow lights have just a specific wavelength I'm worried that in a short distance it burns the seedlings.

10W COB LED

[RorBurg56]

Tbh 10 w is a bit weak sauce. My old indoor setup used one large hanging 100 w led about half a meter or a bit more up and several separate gooseneck lamps (3) each with 50w capacity at closer range. I never burned anything and use the 100w and one 50w gooseneck for seed growing now.

[c4ctim4n]

Tbh 10 w is a bit weak sauce. My old indoor setup used one large hanging 100 w led about half a meter or a bit more up and several separate gooseneck lamps (3) each with 50w capacity at closer range. I never burned anything and use the 100w and one 50w gooseneck for seed growing now.

Thanks for your reply.
Yes 10 w is weak and for this reason i want to decrease distance to compensate lack of enough power! does it work?
you don't change distance for different phases of growing seed? i mean is it ok to have high amount of light at the beginning of planting seeds?

[RorBurg56]

I have recently moved seeds from one indoor location where they had mostly just a 3 headed 66 watt lamp, they are larger now and I just got a greenhouse so they get a better position with the main lamp. It's alot higher than most so I was using it to supplement the closer lights. Seeds are under a large clear plastic tub overturned with capillary matting. Just measured and the big "sun" lamp is abt 41 cm above and the double 50 w lamp is about 11 cm above. The clear plastic tub cuts down intensity a little, which helps because there is an hour of natural light coming through during the day. Seedlings in place abt 2-3 weeks now and are fat and dark green.

Bringing it closer is the right thing to do. I know ppl use low power led strips at v close range successfully. If your seedlings are condensed close together then maybe 1 chip might be OK very close, but I'd suggest a series in a row might be brighter. Either way I'd just test to see. I used most of my lights to grow larger plants before so I bought strong lights. Seedlings seem to appreciate them too so I haven't bought any others.

[RorBurg56]

Also I just use timer plugs to control the exposure rather than changing distance

[c4ctim4n]

Also I just use timer plugs to control the exposure rather than changing distance

Thank you @RorBurg56 for your reply

What type of light do you use? As you know there are a lot of options when in comes to growing. According to your experience which one is better for cactus growing?
And about changing distance i meant that: is it necessary to control amount of light by changing distance at early days of planting seeds? For example is it OK for young seedlings to be 10 cm away from 50 w light or it's too high for them?!

[RorBurg56]

I feel I have to clarify first I used lights for abt 2 years in relatively constricted setup and with limited cash moneys to blow on lights. First, I've used "warm" full spectrum lights and "cool" ones and basically found that the warmer (more yellow tinted) lamps seem to pull slightly more weight, although both effect growth similarly. The warm lights such as the 50w gooseneck and 100w sun lamp cause nice blush on my large echeveria and aeonium and the heat would usually trigger flowering when brought inside for winter. I also use fluorescent tube lamps screwed to the underside of metal shelving to grow smaller and maybe light sensitive plants but supplement this cool spectrum with a wall mounted warm 50w gooseneck. I use stronger lamps and try to give more space than is needed because I feared burning too. Will post some current pics.

[RorBurg56]

I've never measured lux before but did for this. Top shelf maxes at 4k near the edge, second shelf is 3.5k at edge. Top of tub in center if I lift the lamp heads up so as to avoid direct glare and its 10-11k. If I put it right under a lamp head, 65k...

Seems strong lol, and no burning. (OK I killed one aloe the day I got that light but nobody gets to know that)

[RorBurg56]

Here are amazon links for the two lamps used on the tub. My other lights don't exist on amazon anymore and the first of the links says it's not stocked, sadly. But the specs r there at least. I recommend the first or one like it if u can find. The rectangular bulbs are the best shape imo. And you can attach foil hoods to the easily to increase lamp focus. They get warm but not hot, even with a hood.

Double headed warm goose with rectangular bulbs, my first and favourite lamp: https://www.amazon.co.uk/gp/aw/d/B07MNF ... asin_title

Big 100w sun lamp. This was definitely more useful for mature plants but I haven't tried not using it since things grow well so forth. https://www.amazon.co.uk/gp/aw/d/B07PNG ... asin_title

[RorBurg56]

Idk if you would even be looking at these lights or focusing on less powerful setups. If u do use small lights, think about using mylar or foil on nearby surfaces to increase "efficiency of lighting“, or whatever the correct term is.

[RorBurg56]

Oh yeah, definitely I used weaker lights before moving them to here, 3headed 66w cool full spec at v close range. It worked fine. But it's still not really "weak". I'm actually about to sow directly into the tub as is now and see how seedlings fare. Maybe it will be too strong but I feel it will be ok

[Download]

Aim for 5000 to 10000 lumens per square metre running 12 hours per day. Distance doesn't matter unless the lights are physically hot which might burn the plant.

[c4ctim4n]

Aim for 5000 to 10000 lumens per square metre running 12 hours per day. Distance doesn't matter unless the lights are physically hot which might burn the plant.

It doesn't matter how shine is the light? I mean if it's very shine but not hot doesn't hurt plant?

[c4ctim4n]

I feel I have to clarify first I used lights for abt 2 years in relatively constricted setup and with limited cash moneys to blow on lights. First, I've used "warm" full spectrum lights and "cool" ones and basically found that the warmer (more yellow tinted) lamps seem to pull slightly more weight, although both effect growth similarly. The warm lights such as the 50w gooseneck and 100w sun lamp cause nice blush on my large echeveria and aeonium and the heat would usually trigger flowering when brought inside for winter. I also use fluorescent tube lamps screwed to the underside of metal shelving to grow smaller and maybe light sensitive plants but supplement this cool spectrum with a wall mounted warm 50w gooseneck. I use stronger lamps and try to give more space than is needed because I feared burning too. Will post some current pics.

Thank you for sharing your photos. it seems very good and i hope you will get fantastic result . Unfortunately i haven't access to amazon. I have limited options for light types and limited space too . i'm going to build a custom light by putting different lights together and i hope it works

[mikethecactusguy]

10,000 lux is shaded direct sun. You need a minimum of 10,000 at plant surface. Not what the bulbs say not in the general area. Plant surface.