I use grow lights a lot, and I always have them connected to a plug-in timer. There's no way I'd remember to turn them on and then off again to give the plants the proper amount of light. Check Amazon or any hardware store, you can get them for $10 or so and not have to worry about it again.

Not sure what style, brightness of your grow light, but generally they are set close overtop the growing area. Can you post a pic of the light and container?
I am not sure the light affected which sprouted early. Some seeds do better if 'seeing the light' but not sure that applies to radish.

https://www.highmowingseeds.co...

In practicality, Light intensity doesn't have a direct effect on germination, but HEAT does! All light, especially light from fluorescent tubes and even more so from incandescent, will warm the soil. Yes, there is definitely a difference in soil temperature depending on how much light reaches the soil. Remember your physics class: the farther away from a light source, the less light intensity(and indirectly, less heat). The inverse square law applies here: light intensity is reduced by the square of the distance. That's a big difference.

So the soil near the light is warmer, causing faster germination. Unwittingly, you performed a sixth grade experiment: The Effects of Light and Temperature on Radish Seed Germination.

@Leftwood

@sallyg good keeper article

Here's pictures of the setup, and the seedlings. They're red, blue, white lights, I can't feel a lot of heat coming from them. The seedlings are turning yellow? Should I take the wrap off, maybe holding to much moisture?

Put that light Much closer down, and vent or remove plastic.

I was also wondering about the plastic wrap. Radish is a cool-weather crop. I'm not sure that they're happiest in a warm, humid environment. What is the ambient temperature in that room?

Here's how close my light is to my radish seedlings. 6 inches. And it could be closer. And notice how short my seedlings are, seed leaves right on the soil. That is desired, not long stems reaching for the light.

I put the wrap on to keep up the humidity, as the house is really dry. I did just pull it off. I put the grow light higher so the light reached the length of the container, but I'm going to lower it & move it to the opposite side. I'll have to move it back and forth by lowering it. It's 68 in my room & the house. I have a indoor temperature gauge. Thanks everyone for the advice, this is the 1st I've used a grow light and grown from seeds, so it's all new to me.

Yes to all the previous comments. And I don't think you seedlings are turning yellow, they haven't turned green yet. Notice that the yellow ones haven't been up as long. With adequate light, seedlings are green directly out of the ground, but if light is lacking, it will take more time to develop green (or they will stay yellow).

Removing the plastic completely all at once can be drastic. Here's what I would do: First slit the plastic lengthwise the whole length to decrease humidity, and move the light twice as close. Would that make it 1 ft away? it's hard to know for your pics. Leave it this way for a few days. You will probably find that growth will stifle as the seedlings adapt to new, better environment. As long as the seedlings still look good, you will be able to increase the light and open the plastic more and more, until you completely remove it.

You're doing great! Please don't take my comments as criticism. Rather, critique.

It's all good Sally! I'm learning a lot and appreciate all the comments and advice. Thanks.

And here are my radishes damping off because I left them covered too long, and too wet

What is 'damping off' mean? I can't see any different, what am I missing? I was/am worried that my soil is too wet, but can't figure out how to dry it w/o affecting the seedlings. Here's mine so far. The covering is tully, to keep my sister's plant eating cat out of them.

It's a fungal infection of seedlings

From the University of Wisconsin:
"What is damping-off? Damping-off is a common and fatal disease that affects all types of plant seedlings. The disease is most prevalent when seeds are germinated in cool, wet soils. Fortunately, seedlings are susceptible to damping-off for only a short period following emergence and eventually outgrow their susceptibility to the disease as they age."

More information here https://hort.extension.wisc.ed...

So this is what they look like now. I did pull a few out as they were too close to others & really gangly. They're a bit tangled as I had to tip the container to drain water out, way too much water. Aren't there supposed to be secondary leaves developing. The ones I pulled had heathy roots on them. When they develop more can I move some to space them out better?

Update: So the seedlings stopped developing, & were just flopped on the soil, some broke or bent. I tried adding more soil to support the legginess, as it had compacted since I started. Nothing. I also noticed that the top 2" where I put the seed mix was drying out but the bottom layers were wet. So take two: I decided that the plants weren't going anywhere so I pulled them all out & started new.

I took out half the rocks, mixed the seed soil in with the regular/compost soil (I have worms! Yeah) to make the moisture level more even & aerate the regular soil & put both of my grow lights on the container, one on either side, & lowered them. I planted the seeds more organized & don't water, only spritzed the surface.

Fingers Crossed. Thanks for following, & the encouragement.


Unfortunately I only have the 2 lights so the cuttings I'm trying to root are going without. I don't have a place to put in the sun.