Grow High Light Plants Indoors Without Hydroponics

There is a lot of interest in growing high light plants indoors these days and I supposed it’s because as of March 2012, growing Medical Marijuana or Cannabis is legal in 16 states. And even here in Alabama where getting caught growing even one plant will land you in jail for three years, I can find books for sale on the subject at every major book store I’ve visited.

I’ve grown houseplants for years but when I tried hydroponics and I failed miserably. I could grow lettuce and other quick growing plants but when I tried tomato plants they always died when they got larger. I’ve pretty much decided that the small hydroponics kits you see on sale on-line and on eBay may have all of the chemicals you need to grow, but they don’t have what you need to maintain the correct liquid hydroponics cocktail to grow large plants or to grow a plant to flowering or budding stage. The big guys can do hydroponics because they can afford to buy the expensive equipment needed to monitor their chemical solutions.

This article is about growing high light plants like tomatoes, peppers, marijuana, etc indoors without using hydroponics. To be successful you need a bright light source that generates minimum heat and a enclosure to contain and focus the light. Everything you need except for the LED Grow lights should be locally available. We used our own Grow Sun Grow lights in this project because they work very well.

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Step 1: Select Cabinet

The first item you need is a Low cost cabinet. LED Grow Lights are extremely bright and the cabinet will help contain the light around plants instead of lighting up the entire room with wasted light. The light will bounce off the cabinet walls and back to the plants giving you maximum light penetration through the entire plant. This also prevents nosy neighbors from calling the cops and reporting the pretty violet light that would be coming from your spare bedroom without an enclosure. And the last thing I want is the local police knocking down my door only to discover I’m growing tomato plants

I bought this 70"H x 48"W x 20"D Wood Composite Multi-Purpose Cabinet from LOWES for $108.00.

Step 2: Cabinet Details

I chose this cabinet because the inside is divided into two equal sides, each almostly perfectly square and large enough to grow two separate plants. The cabinet also has a upper section I can use to mount everything neatly out of the way.

Picture of cabinet before I installed the doors or did the modifications. Each side is perfect for the pots I bought

Step 3: Buy the Right Pot

The second items you need are two large pots and the larger the better. You can’t grow large plants in small pots and expect them to do well. I picked up two 17″H x 17″W x 21-1/2″D Plastic Pots from LOWES for $17.48 each. These pots have knockouts in the bottom that need to be punched out for proper drainage. I also picked up two low cost drain pans while I was there.

Step 4: Buy the Right Soil

The third item you need is very good potting Soil. Skimp on soil and you won’t get the healthy plant growth you need no matter what else you do. And what about filling pots with garden soil? Garden soil works outside because the plant roots can grow to where they can find food. Put garden soil in a pot and the roots can only fill the pot. So buy the good stuff – it’s cheap enough. I bought enough Miracle Grow Moisture Control Potting Mix to fill both pots.

Step 5: Provide Ventilation

To grow inside a cabinet you need to provide plenty of Ventilation to keep the humidity down. I used two 120mm PC cooling fans for ventilation. You can buy these at your local Radio Shack, pull them out of a couple of old PCs or you can buy them on-line for less than $5.00 each. You also need a single 12 VDC power supply and any wall plug style DC power supply should work fine. Also, unless you want to turn the lights on and off every day, invest in a lighting timer. I bought a timer at LOWES with 4 outlets for less than $10.00.

Step 6: Choose Good Lights

You need a good grow light that puts out very little heat and the ideal candidate is a LED grow light. Good LED Grow Lights are compact and run so cool that you put your hand on the light when it’s running. Just make sure you have at least a 40 Watt LED grow light - smaller lights, no matter how much cheaper they are, are a waste of your money because they don’t put out enough light. And don’t bother with a High Pressure Sodium and Metal Halide grow light. Either of these lights will turn your grow cabinet into an oven. Also florescent grow lights small enough to fit inside the cabinet don’t put out enough light in the targeted bands that LED grow lights do.

Step 7: Modify the Cabinet

I won’t bore you with re-typed assembly instructions when the instructions that came with the cabinet work fine. But you do need to do some simple modifications to pull the excess humidity out of the cabinet and to concentrate the light so it’s as bright as possible.

The inside walls of the cabinet I bought were tan colored so I painted them bright white before I started assembling. You can use any white paint, even inside house paint. I used bright white glossy spray paint and 2 cans were enough to cover everything I needed to paint.

Next I followed the included instrictions to assemble the cabinet.

I started the modifications by drilling 1-3/8″ vent holes to the outside of the cabinet and a 1-3/8″ hole for the power cord.

Picture 1—Drill a 1-3/8" hole through the back, top of the cabinet for a extension cord.
Picture 2—Drill 1-3/8" vent holes along both sides of the top.
Picture 3—To protecting the finish, drill the holes from the inside until just the drill tip pokes through then finish by drilling the rest from the outside.
Picture 4—Completed vent holes along one end of the cabinet.

Note: Instead of simple exhaust holes dumping back into the same room you can mount a bathroom exhaust fan in the top of the cabinet and then run flexible exhaust fan duct to the outside.

Step 8: Add Main Ventilation Holes

Drill two 3-1/2″ vent holes holes between the top boxed in area of the cabinet and the lower sections

Picture 1—I used a 3-1/2" hole saw for the main vent holes
Picture 2—Drill one centered hole between each lower area and the top shelf of the cabinet.
Picture 3—Drill a 9/16" hole behind the main vent hole for the grow light power cord. You can see the 3-1/2" vent hole in the picture.
Picture 4—Picture of one of the inside vent and power holes from the bottom. You can see the inside of the cabinet top through the hole.

Step 9: Wire the Fans, Mount the Fans & Lights and Final Wrap-up

I added a power jack to the fan wires so I can easily replace the power supply if I need to. You could just as easily straight wire the fans to your power supply. The jack I used is P/N CP-011A-ND, ordered from DigiKey.

Picture 1—The 120mm Fans I chose for the project
Picture 2—Cut the PC power connectors off the end of the fan wires then strip back the outer covering to expose three wires. The black and red wires are negative and positive power. The yellow wire is the tach output and not needed.
Picture 3—Cut the yellow wire off - you don't need it.
Picture 4—Then solder both fans to the power jack so both fans will turn on whan you plug in the power supply. Or you can cut the power plug off the end of the power supply cord and straight wire the fans to the power supply.
Picture 5—Mount the fans centered above each main vent hole so that the fans pull air up into the top shelf area.
Picture 6—Both fans mounted and plugged into the power supply. You can see the power supply plugged into the end of the extension cord in the middle of the picture.
Picture 7—Mount the lights directly opposite from the fans. Our Grow Sun grow lights include intergal mounting brackets that can be used to surface mount like I mounted these or they can be hung from chains.
Picture 8—Here is a better picture of the mounted Grow Sun grow light. You can see the edge of the vent hole by the mounting bracket.
Picture 9—I used this light timer from Lowes because it has 4 outlets. I plugged the two plant light power supplies into 2 of the outlets then plugged the timer into one of the open extension cord outlets.
Picture 10—Here are the lights below the shelf and the power supplies and fans on top. You can see that everything fits with plenty of room left over for supplies. You can also see how bright our lights are - they are much brigher than the camera flash.
Picture 11—Here is a picture showing the Grow Sun grow light turned on. The light looks violet becase we output only red light and blue light.
Picture 12—And like I mentioned earlier, our Grow Lights run so cool you can place your hand on them. Try this with a High Pressure Sodium or Metal Halide lamp and your hand will be blistered in seconds. Also, you can see that this light is much brighter than florescent grow lights.
Picture 13—And a straight on picture of our LED grow light mounted in the cabinet. Each 1 Watt led is being driven full power and the Surface Mount LEDs are so bright that everything around the light looks black to the camera.
Picture 14—One of two tomato plants we are growing in our cabinet. And yes, we are growing tomatos and not Medical Marijuana or Cannabis. Growing Pot is illegal in Alabama!
Picture 15—Tomato plants inside the cabinet. The light gets dimmer twords the bottom because the doors are open and the light is escaping out the front. Once the doors are closed the light really brightens up from top to bottom.

Step 10: Final Grow Cabinet

And a final picture with the doors closed. You can see that some light escapes but it's very little. You could add gaskets but the exhause fans need to be able to draw air in from the outside of your new grow cabinet.
Thanks, Tom Hargrave

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19 Discussions


4 years ago on Introduction

how long would you keep the plants in there? poor things, a marijuana plant needs at least 3 meters of space, if you want them to thrive completely and not hold them back from their true potential.

1 reply

This was a fun project with tomatoes and peppers. Since then I've moved to a Aerogarden and will probably set up a greenhouse this fall. But still no pot, it's illegal in Alabama.


5 years ago on Introduction

Something like 21 states now able to grow Medical Marijuana I think. The Grow Sun lights are nifty, the website states 350Ma, and a total of 54 LEDs at 1 Watt each, then it says:

  • "Low power consumption – draws only 58 watts of power
  • Very high efficiency – 54 of the 58 watts consumed by the high intensity LEDs"

If you are running at 110 Volts with 350Amps that equates to 38.5 Watts or at 120 Volts it is 42 Watts using this calculator that shows 42 Watts it seems Grow Sun are driving the LEDs at about 78% capacity (not the full 58 Watts) which is quite high compared to 3 Watt versions. I understand that commonly the 3 Watt LEDs are driven at around 55% to 60% of their capacity so they last longer, maybe that is just 3 Watt models versus 1 Watt models. For example here they state their full spectrum lights are run at 120VAC@2.1A with a power consumption of 250 Watts from 150 X 3Watt LEDs, this is about 55% power.

Looking further into the specs I am also keen to know if the gaps in the spectrum were an issue? Seems there is nothing between 500 and 620 nanometres and nothing over 650 but I understand PAR, the Photosynthetically active radiation range goes over 700?

People say that full spectrum is the key to really good produce but I just never know.

4 replies
Tom Hargravejames26

Reply 5 years ago on Introduction


What you don't see is the control circuitry running each string of LEDs in the fixture. These are not straight wired LEDs, that are arranged in 7 banks & each bank has a SMT LED controller designed for the automotive industry that manages power to the string. The controllers keep each string at a constant 350 ma. We are pulling 2.4 Amps from a 24 VDC power supply running at 85% efficiency. My efficiency statement comes from backing out the power consumed by the controllers themselves. Knowing the current is constant I took the 350 ma X the voltage dropped across the controllers to calculate the power they consume.

I looked at 3 Watt LEDs and even did some temperature measurements & light measurements from a few samples. Based on the measurements I made I believe the 3 Watt LEDs are the exact same technology, only they are being driven harder and are less efficient than 1 Watt LEDs. Their only advantage is space assuming you can find a creative way to cool them.

Also, based on temperature measurements I went the opposite direction and designed a grow light based on 720 - 20 ma Amp SMT LEDs, and yes that's seven hundred and twenty! I attached a image of the raw card drawing. I built one of these so far and it runs very cool. The advantage of 20 ma SMT LEDs is they are not being over-driven like 1 watt or 3 watt LEDs and you don't have the heat issue.

New Grow Light.JPG
james26Tom Hargrave

Reply 5 years ago on Introduction

Hey Tom, I am learning more and more about LEDs. I did a search for the '20 ma SMT LEDs' and Google thinks 'SMD'? I see SMD means surface mount and SMT means surface mount technology and they are the same thing. Glad I have that sorted! What is the advantage of say using standard 20mA, over say 1W, 3W and 5W versions.... why are the LED grow lights moving to higher Wattage LEDs? Is it purely to save on space, cost or maybe intensity?

Tom Hargravejames26

Reply 5 years ago on Introduction

Technically SMT is Surface Mount Technology and SMD is a Surface Mount Diode (the part).

Regarding diodes and power, the LED manufacturers are getting 1 watt, 3 watts and 5 watts respectively by over driving (pushing a lot of current) through the diodes. This creates a lot of heat which is why you have to use a heat sink with high watt diodes.

The LED grow light manufacturers are going to higher wattage LEDs to increase light density in a small fixture. But I also believe there's a little bit of a "LED Arms Race" going on and if mine's bigger than yours I will get more sales than you will!!!! This also means that the day a 10 Watt LED hits the market several manufacturers will be advertising their 10 Watt LED based grow lights for sale!

There is also a lot of misdirection in the industry..I base this opinion on the fixtures I actually bought and measured. The lights just weren't doing as advertised, then when I would measure the actual power being drawn by the fixture I knew right away what was going on. In most cases the fixtures were not drawing enough power to support the amount of light they were supposedly putting out. I won't post a list because that was over three years ago and some of them might have actually gotten their act together. Maybe....


5 years ago

love it but HPS lighting is really the onlylighting you can use or another specific grow light or bulb

1 reply

I agree that HPS is a superior light as long as you can deal with the waste heat. But you aren't going to put a HPS light in an enclosed cabinet like this one. I ended up growing these two plants successfully and I picked some peppers of the pepper plant. I learned through this whole process that:

1. Tomatoes are very difficult & they won't pollinate without some outside assistance.

2. No matter what you grow in a cabinet, the upper growth will shield the light from the lower growth causing the lower leaves to die off. I believe that growing plants in a cabinet or enclosed box is a good idea, but only for something fast growing like lettuce. Anything taller with structure & a long growing season needs to grow in a room where the plant can spread out and light can reach in from the sides.


7 years ago on Step 10

have you had to reinforce the cabinet
very good instructable.. what price where each of the lights because i know they can be expencive

5 replies
Tom Hargraveandybuda

Reply 7 years ago on Step 10

I have not had to reinforce the cabinet. We designed the light ourselves but you are right, if I had to buy them they would be about $300 each.


Reply 6 years ago on Introduction

same here I am using standard CFL bulbs from a hardware store, not the special grow light ones, the only thing is with those is you have to have them less than 8 inches away so the plants can get the useful waves of light. i use cool daylight (6500k spectrum) for the veg stage then switch to warm white in flowering stage (2700k spectrum)

Tom Hargravediy_bloke

Reply 7 years ago on Introduction

They aren't for sale right now because we are doing a redesign. We discovered a heat issue while the lights were being tested. It wasn't a safety issue, it was a performance issue.


6 years ago on Introduction

I've had a lot of success using a heliostat to bring natural outdoor sunlight into even a north facing room. Then you have plenty of light for your indoor garden. You can get a heliostat at for example.


7 years ago on Introduction

Actually, the last thing I wld want is the local cops knocking on my door and discover I am growing illicit substances.
As I am growing tomatoes they can do all the knocking they want

2 replies
Tom Hargravediy_bloke

Reply 7 years ago on Introduction

I agree with you and I grow peppers & tomatos - problem is, when they knock they don't stop & say "please, can I come in". They come in, assume guilt even though you only have tomatos or peppers growing under your light. Then they run on that assumption of guilt and search your whole house. If they find weapons in your house, they gather them up & have you explain each one even though they are legal.

The safe thing to do is to not let the light escape where it will draw nosy neighbor's attention.

diy_blokeTom Hargrave

Reply 7 years ago on Introduction

that is true: I run just a bright light in my office and neighbours already think i am in the growing business + police dont't like disappointments so they will clear your tomatoplants, seize yr lights, name and shame you and by the time it is all sorted out you won't get back your stuff