LED Growlights 2021

[Stevepeat]

I have now transferred my seedlings to a light enclosure using a Mars Hydro SP 150 LED light bar. The enclosure was made entirely from a bed base I salvaged from a neighbour. It needed hardly any cutting, just screwing together. The enclosure is 42 cm x 90 cm and 90 cm tall. This is just short of the 1.5 x 3 foot coverage of this light. It has white hardboard on three sides, currently an open roof and a blackout roller blind on the front to shield the room from the very bright light as it is on a shelf above our television! The light is currently 45 cm from the floor of the enclosure. The internal temperature range has so far been 17.5 to 25 degrees C.

MG602866.jpg (96.23 KiB) Viewed 1389 times

I am interested in the concept of using LED growlights indoors for those who cannot have a greenhouse and for growing seedlings all year round and possibly providing better conditions for winter growing plants in the UK. Much progress seems to have been made recently and the lights now available are white rather than the blurple which was popular. There seem to be a few options (Mars Hydro being a recommended range) but these tend to have a square format for grow tents because of a common use for these lights (weed). The SP 150 is more of a bar format and includes IR and UV as far as I understand.

I have also recently joined a facebook group which promotes lights only available directly from a Chinese factory developed by one of their members, specifically for cacti and succulents. These are dimmable, available in 60, 90 and 120 cm formats and cover a shelf of 40 cm wide. This seems to be a better format for indoor shelf units. I am including the link and would be interested in any comments anyone might have. If these prove to be a good option, a group buy can be arranged.

https://www.facebook.com/groups/7663161 ... 245742987/

[esp]

I have also recently joined a facebook group which promotes lights only available directly from a Chinese factory developed by one of their members, specifically for cacti and succulents. These are dimmable, available in 60, 90 and 120 cm formats and cover a shelf of 40 cm wide. This seems to be a better format for indoor shelf units. I am including the link and would be interested in any comments anyone might have.

I get good results with standard 60cm 20W LED batten lights. Available in 30, 90, 120cm lengths also, 3 would probably be needed for a 40cm shelf width.
Full power and close to the plants seems to be needed for cacti and succulents, even as fairly young seedlings. A dimmer capability would be unnecessary.

[Pattock]

From the spectrum they show for the Mars Hydro SP150 the short end stops completely at about 410nm. No UV at all. Not that you would want it for most plants except weed.

I just use a mixture of warm and cool white 13ishW Philips household LED bulbs. The ES fittings are easy to buy and easy to replace and reliable. I can spread them out to fit the space, raise and lower them individually and have multifocal sources. Philips should know what they are doing with the engineering and corporate responsibility.

[KarlR]

Neat setup! Looks nice and tidy. My wife would have me admitted if I attempted to put something like that over the TV

Thanks for the Facebook link. The prices are not what I would call cheap for being directly from the factory, if that's true. But then I haven't bought anything from China post pandemic so i maybe prices have gone up considerably.

I've been growing c&s under lights for over a decade now. Mostly for seedlings these days, and the more tender succs over winter. I switched from MH bulbs to all LED a couple years ago. I much prefer the MH bulbs I used (2x400W) for the actual quality of the plant growth, but LED is more customisable, produce a lot less heat and, at least for cacti and succulents, allow you to cover a much greater area with decent light.

I have a setup in the basement with 5 shelf units with 4 levels on three of them and 1 on the last two. I've tried a few different LED systems from China and generally been dissatisfied with them. Currently I almost only use Samsung full spectrum LED fixtures @6400K of 20w and 10w (60cm and 30cm). It's not made for plants specifically but it's just as good. I have about 60 of those fixtures installed at the moment, as well as two 120w LED quantum boards, but only using half of them now. When they're all up and running they draw 1200w, which isn't an issue during winter with all the heat produced, but becomes too hot in the summer.

Adding a photo for reference. No recent photos and this is just a frame from a video, so apologies for the terrible quality...

[N.D.]

When they're all up and running they draw 1200w, which isn't an issue during winter with all the heat produced, but becomes too hot in the summer.

How many watts per square foot (or meter) does this translate to, and what is the ambient temperature in the room?
I have a very similar set up with 40W/sq.ft., and I need a massive cooling system to keep temperature to around 15C. I suck in outside air using two 5-inch fans (for a total grow area of 8 feet). This cooling works when outside temperature is between -20C and 0C. When it warms up above freezing outside, the systems cannot keep my plants at 15C any more.

[KarlR]

When they're all up and running they draw 1200w, which isn't an issue during winter with all the heat produced, but becomes too hot in the summer.

How many watts per square foot (or meter) does this translate to, and what is the ambient temperature in the room?
I have a very similar set up with 40W/sq.ft., and I need a massive cooling system to keep temperature to around 15C. I suck in outside air using two 5-inch fans (for a total grow area of 8 feet). This cooling works when outside temperature is between -20C and 0C. When it warms up above freezing outside, the systems cannot keep my plants at 15C any more.

Not 100% sure about the measurements of my shelves, but I think this translates to ca 200W/sq.m. That's with the Samsung LED fixtures of 20 & 10W (80W per shelf). My two Quantum LED boards work out to 300W/sq.m., while the MH bulbs were 1000W/sq.m.

The ambient room temperature is probably between 20-35C depending on time of year and time of day (and the number of lights that are on). It's difficult to ventilate the room better as there's no window and it's below ground level. I have fans running, which help, and the room is open to the rest of the basement so it's not too bad.

Still, it's not ideal for mesembs and high altitude cacti, but is fine for seedlings and all the succs and cacti that don't mind those temperatures. And then there are lots of succs and cacti that love being warm all the time.

[esp]

I'm nearly always surprised by the distance between the lights and the plants when I see photos of LED set-ups.
Simply having the lights closer will enable fewer light to be used, hence less power consumption and heat production. If there are taller plants included, this becomes less feasible, but not for trays of seedlings

[KarlR]

I'm nearly always surprised by the distance between the lights and the plants when I see photos of LED set-ups.
Simply having the lights closer will enable fewer light to be used, hence less power consumption and heat production. If there are taller plants included, this becomes less feasible, but not for trays of seedlings

Having the lights closer means they cover a smaller area. It's no good having one light 10cm above the plants if that means the light doesn't hit 75% of the plants on the shelf. There's also a very big difference in the need for light depending on whether the lights are just for starting off seedlings for a couple of months. Then you don't need much, but beyond 6 months to a year you need more light. There's a balance between the area you want to cover and the distance of the lights. It would be better to have the lights closer than what I have but then I would need more lights. But with more lights there would be more heat. So that's also a balancing act. For me there's also a practical issue of wanting to be able to look at the plants, or extract a pot or water from above without having to take out the whole tray.

[N.D.]

I'm nearly always surprised by the distance between the lights and the plants when I see photos of LED set-ups.
Simply having the lights closer will enable fewer light to be used, hence less power consumption and heat production. If there are taller plants included, this becomes less feasible, but not for trays of seedlings

I do have my lights almost touching the plants, but this is not to maximize light; it is co conserve vertical space. I measured light flux at the plant level as a function of distance, and found out that there is almost no difference (at least for enclosed space with reflective walls). I am aware of the inverse square law, but it is only applicable to point light sources. In our case the light source is a tube (or even a plane). Inverse square law does not apply here, and I confirmed it experimentally. In my case, light flux begins to fall off only at very significant distances; it also goes up only at very close distances (about an inch from the light tube).

[SimonT]

Is there a recommended PPFD range for growing cacti from seed?