LED Grow Light

[jeff5may]

Don't burn 'em. The first growth from the "seed leaves" is not especially light dependent, as the baby is feeding off the seed. In this phase, it is normal for the plants to stretch. It is also the time when the leaves are most sensitive to light. By the time the leaves show signs of stress, it's too late, and often the babies wilt and die.

Then again, you may not have enough output to do serious damage. I have zero practical experience growing with LED light sources. However, you have close to the same output as a 75 Watt HPS bulb, which will decimate seedlings up close. I have heard from others that the red+blue fixtures put out way more useful plant-growing light than they appear to.

[natethebrown]

So far, things are looking pretty good.



As of right now, the grow light sits about 4" above the tallest seedling pots. A quick Internet search indicated one needs approx. 60W/sq ft of growth. I say approximately because that is for a Pot Plant (once again, they seem to be the only ones that do any scientific research in this stuff), and that may not apply as much to veggies. With the grow light about 4" above the top of the seedling pots, that puts a lighting footprint of 3.3 sq ft of illuminated area or 18 W/sq ft.

Comparing to images I took two days ago, it seems like I did have an inadequate amount of light. You can see there isn't much vertical growth in the seedling compared to 2 days ago, and the stem is darkening. I haven't noticed any indications of leaf burn or signs of stress but I will keep my eyes peeled.



The real indicator that I am on the right track is when their second leaves start to emerge. I will be observant for signs of stress.

[jeff5may]

Any updates? How are the seedlings doing?

[natethebrown]

Originally Posted by jeff5may

Any updates? How are the seedlings doing?

To be honest, not great. Nearly all of my seedlings still do not have their true leaves yet. Contrast that with my cucumbers and green beans I directly sowed in my garden only 20 days ago, they are shooting up like weeds.

[natethebrown]

So, after a long delay I have finally gotten around to seeing what went wrong with my seedlings this year. I came up with 3 possible variables that caused all of my seedlings to fail:
1) Not enough light intensity from the grow light
2) Too cold in the garage and stunted growth
3) Poor soil

After replanting a bunch of basil seeds and pretty much getting the same result again, even though they were in direct sunlight, I figured I needed to test the soil.

I went to one of the big box hardware stores and got 3 other types of soil, allowing me to test 4 total soils:
1) Jiffy All Natural Seed Starter Mix
2) American Country Side Top Soil - My original soil that I used
3) Miracle Grow Nature's Care Potting Mix
4) Miracle Grow Seed Starting Potting Mix

For this test, I used the seeds that I had: Roma Tomato, Cherry Tomato, Jetstar Tomato, and Kale. Each pot had exactly 3 seeds in them, and they were all started at the same time, on 7 June 17.

Here is the experiment layout (from left to right in the pictures):
Pots #1) Jiffy All Natural, with seeds soaked for 1 hour.
Pots #2) American Country Side
Pots #3) Jiffy All Natural
Pots #4) MG Nature's Care
Pots #5) MG Seed Starting Mix

And here are the results as of today:


A closer look at Pots 1 and Pots 2:


A closer look at Pots 3, 4, and 5:


From the results, it is quite clear that the soil I was using this past winter was garbage! Right now, the current winner is MG Nature's Care (the pots in the middle of picture #3), but I am going to wait a little longer before I can conclusively say it is the best seed starting medium. Also, I plan on running this exact same experiment under my grow light to see if I get similar results.

[jeff5may]

I used the mix the local commercial greenhouse uses to start all their fast growing annual stuff this year. It's like generic pro mix.

[where2]

Thanks for the updates Nate & Jeff. At some point, the 20+ acres of farmland my wife and I have may benefit from this soil and lighting data. For that matter, the 10 bare root blue spruce seedlings I planted last summer may have benefit from the soil data, had I known it at the time...

[natethebrown]

Originally Posted by where2

Thanks for the updates Nate & Jeff. At some point, the 20+ acres of farmland my wife and I have may benefit from this soil and lighting data. For that matter, the 10 bare root blue spruce seedlings I planted last summer may have benefit from the soil data, had I known it at the time...

Glad I could help. It is crazy how quickly technology has transformed. Even though I did this project earlier this year, these LED COBs are old technology. If I was to build this grow light again, I would go with these:

110v led cob grow light | eBay

[natethebrown]

And the latest picture as of last night:


Any guesses as to which one was my original soil?

Anyways, right now I would say Jifffy All Natural seems to have faster growth but MG Nature's Care seems to have a better propagation rate. Ultimately, I think any growth medium is better than the cheap stuff.

Also, I did get this same (well nearly the same, a couple of different plants since I ran out of seeds for two) experiment setup under my grow light last night. As soon as they start sprouting (7-9 days from now) we will see how well the grow light does compared to actual sunlight.

[Sully01]

The babies are coming along nicely. Your lighting set up is legit. Looks like you just need a few lava lamps and you're all set lol!