Grow Lights


This may have been covered in this thread but I’ll ask anyways. Is it true that lights weighted in the 6500k (bluish white) range are better for seeding’s vegetative growth? Whereas for fruiting you’d want more in the range if 2-4k (orange-red)?

I use 6.5k T8 lights for getting my seedlings going after they sprout. They seem to like them.


That’s a good point- Iwouldn’t be thrilled to see the reflection in the sliding door glass either. I’m guessing the neighbors might also think a purple glow from my house was a bit strange…What is the best way to know if the light looks mostly white?

This one says “Using effective full spectrum 410-780nm sunlight spectrum for plants”, but someone answering a question said “They’re a light pink with a hint of rainbow”.

Is there a big benefit of COB vs the LEDs being distributed over the entire surface?


You can do full grow of most plants using lights that are 3000 to 4000k, more blue might cause them to stay compact but it will also slow growth to an extent


most of the better led marketers do. :wink:


supposedly a mix is best. most quality leds have a veg switch and a bloom switch that changes the color spectrum that most benefits that plants current growth cycle.


Oh, I never grow them (tomatoes, peppers, some herbs) to maturity indoors. I start them in pods, then put them on a heating pad until they sprout. After they sprout, I take them off the pads and under the lights they go. When they get about 2-3", they get transferred to 16oz cups and back under the lights, until I start hardening them off outside little by little.

This year was funny because right when they were getting about the size for transplanting, it was very rainy and cool. That meant I couldn’t plant them then. So, they just kept getting bigger indoors. By the time I got the tomatoes in the ground (early June) some of them were over a foot tall. Very gangly and thin. I remedied that by stripping off the lower branches and burying them deep. They all turned into robust beautiful, productive plants. That was until the deer helped themselves to them, but I won’t go into that story again.

So, I guess what was I was asking is since I’m just trying to grow them without fruiting, that the 6.5K lights would be a better temp than say 2-5K.

OK I just read your response again, and say if I did use a mix of cool and warm lights, that my plants would get even bigger?


Good light for seed starting and leafy greens would be this:


I ended up dipping my toe into grow lights. I got a few bulbs which fit normal sockets and also got a small (45W) board with 225 LED (Kingbo for $28).

The first 2 arrived (Amazon Prime) and I made a slightly broken box (bottom is intact) into a growing enclosure with aluminum foil. Yes, I know I do things classy :slight_smile:


Along with a couple jujube seedlings and a young fig, the first inhabitant is a potted muscadine. I think it is Fry Seedless (lost tag). I’m particularly excited by this, as my in ground FS hasn’t produced anything in the 3 years I’ve had it. It had the tiniest starts of grapes when I brouhgt it inside about a month ago. I’m surprised that it has been able to size them up while growing in the window. But, I figured that it wouldn’t last and needs more light.

Here’s what the setup looks like with the lights on. Given the harsh light, I will probably only leave it on during the day, when I’m not using the room.

The light on the left is a 24W Apollo bulb with 3 colors (Red- 630nm, 660nm & Blue - 460nm)
The one on the right is the 45W, 225bulb Kingbo with 6 colors- more than half is red (650-660nm) and Red (620-630nm), with a decent amount of Blue (450-460nm) and White (6000-6500K). It also includes a tiny amount of UV (380-400nm) and IR (730-740nm)- 2 bulbs and 4 bulbs.

I know that UV can be dangerous- just how bad is this? I’m guessing that brief exposure to reflected (not looking directly at it) light probably isn’t too bad, but I’m guessing that minimizing exposure would be good.



Looks good. Plz keep us updated on your muscadine progress.



380-400nm is at the end of the UV-A band. I don’t think it will be an issue. But, yeah it’d prob be best to not stare directly at it. Just put on your Ray-Bans when working with your plants. And you might might get a little bit of a tan! :slight_smile:


Plan on adding a white light if you want to work with the plants. “grow lights” are horrible for telling what’s going on. LED flood lights are pretty good for working lights - and they add a few lumens too!

For instance - on my aquaponic system in my classroom, I have a great Kind XL-750 grow lamp. Wayyy too bright to use during class hours. So it runs opposite class-time - i.e. evening/mornings. During class hours 2x50W LED flood lights illuminate the plants so students can view what’s going on.


Few plants Ive got under lights in my closet right now, mostly honeyberry but also a rosemary and buzzbutton in there. These are cheap strips I removed the ‘epiled’ diodes from and added white cobs to. These are on a meanwell HLG power supply capable of about 150watts but dimmed to about half power currently.

Plants on my desk @ work, also a rebuild of cheap chinese strip light, just saved the heatsink as it is fairly substantial. This strip has 3 cobs running at about 15 watts each.


My husband just made and installed a second light bar for the greenhouse, regular 12v LED lights. This one has 3 strips (the first one, above, has 2). The two eight foot bars use about 86 watts, cost for both would be about $30. I’m running them an hour or two morning and evening to extend the daylight, plus all day when it’s too cold and cloudy to open up the insulating curtain/panels. The first one worked well so I’m happy to have this extended help in growing greens now and in starting plants earlier in late winter. Plus it’s really cheery out there! Sue



Nice. Anyone looking at strip lights should check these out. Not super cheap but the 4’ double strips putting out 17340 lm is pretty awesome!


Excuse the stupid, I thought that the pfd said they were to replace T5HO bulbs. Does that mean a straight swap or with modification? What is not supercheap?


My little setup for the strawberries this year. LED 35x2 + 15x2 + 12x3 = Total 124W in ~3’ by 3’ tent.



The price compared to a lot of the chinese strip led lights isnt cheap, but they are some of the best available right now. They arent a direct swap for bulbs, they need a different style of driver than T5s and theres some wiring involved but its relatively simple, no soldering required.


I just got an LED for veggies, but I’m having trouble figuring out how many plants it will cover. With fluorescents it’s obvious because you want the light as close the plant as possible. Is it the same with LEDs? I plugged it in and the thing produces enough enough light to light my entire block!


If it’s white led you can use a lux measurement app for your phone. Intensity depends a lot on what u want to grow. Lower tech method is to use your hand. U should be able to feel the light on your skin, you’ll develop a sense for it after some time. Most plants will suffer from to much heat before to much light. Gud led grow lights aren’t cheap. They save u money in efficiency and lifespan but cost more up front. Cheap led lights are junk with no exceptions.