Introduction: TerraHydro Boxes, the Ultimate Self-Watering Vegetable Container System (aka TeraHydro Box, TetraHydro Box, DIY "EarthBox", or DIY "Grow Box")


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This is a guide to building a 2 different great "EarthBox" systems for next to nothing in relation to the $50 commercial version. The smaller is a more experimental idea and may just be TOO small... the larger will work as well or better than the commercial counterpart. This instructable will cost you about $10 for EVERYTHING for the smaller and about $15 for the larger... I recommend building 2 of which ever you chose to bring down cost... or build 2 of each like I did :)


EarthBox is a commercial version of a "self contained gardening systems". From here on out I will call mine TerraHydro Boxes... lol... my own brand... lol

TerraHydro Box explains exactly what it is though... it is basically a hydro system for growing plants that also incorporates a small amount of dirt for plant stability and fertilizer delivery. Further explanation of the science is in the first step of this project.


The advantages of growing plants in a TerraHydro Box are abundant.

-A place to grow for those without "real dirt" aka large yards

-Requires much less space

-Saves huge amounts of water

-Easy to keep plants well watered

-Almost maintenance free all season after planting

-Huge crop yields

-Easy to grow organic or "regular"

Update!! BOTH the small and large TerraHydro Boxes worked excellent. The Large TerraHydro Box worked much better than the original Earth Box even!! I harvested gallons and gallons of salsa. Way to much in fact, haha... While I still recommend 6 tomato plants for the large THB, 2 would be better for the small one. Six plants was just too much vegetation for such a small area and the plant were a little small from not getting enough light. Check my account soon for more garden projects in 2010! :)

Step 1: How It Works

Here is an explanation or TetraHydro Boxes and how they work. The first image is a cutaway from the Earthbox website and helps you understand what i am saying if you have never seen one.

Essentially, you have a large plastic tub, with a water reservoir in the bottom, dirt on top with a huge strip of fertilizer, and the whole thing acts similar to a hydro system for growing plants and vegetables. If you don't know what hydro growing is, the short and sweet version is: it it a growing system with no dirt, that allows the roots to grow in a large bucket of fertilized water. After taking apart an Earthbox after a season of growth i discovered all of the roots had reached the water reservoir and were doing just that. NOTE: whether you use my build design or not there are two things i know are very important that most other guides overlook. In order for the "hydro" part of the earth box to work the water reservoir has to be absolutely dark, to promote roots and discourage algae, and there also must be tons of hole in whatever device you use to separate the water and dirt. Other wise you end up with wet dirt, like you needed, but root bound plants which is not as good for plant health.

Earthbox is a good system. A great system even. Just wayyy overpriced. My TetraHydro Box is based off the same principles, and i deviate in a few small ways, but usually will tell why i did and what Earthbox recommends instead. For example... Earth boxes recommends only 2 tomato plants per box, yet i have grown 6, even in their box, with tons of success so that is how i do it now. Perhaps they have a reason, or think they have a reason for why you should only plant 2 plants, but i think its just to sell more boxes... lol... alot of the things they recommend doesn't seem like there is a real solid reason tho... i think they pushed the product to market as fast as possible and did not get real exact on how or why you should plant things a certain way. The majority seems like educated guesses from smart people, so i use their instructions as a guide and experiment with my own ideas too :)

Step 2: Material List

I will simultaneously explain how to build 2 different TetraHydro Boxes and I recommend you build 2 of whichever you choose. I need to remind you. The smaller version is experimental!! I have been pushing the limits on the Earthbox since i got it to see how much it can grow, and know that the large TetraHydro Box can grow 6 tomato plants!! But the small TetraHydro box is experimental in that i am now wondering how small the box can be as long as it has essential nutrients and plenty of water.

If you are new to this goring system... just skip the experimental small box, build the large and be amazed!! :)

Everything is nationally available and purchasable at Wallmart and Home Depot. First is the list for each box system and below is a more detail description with important notes on items like the fertilizer and dirt.

Large TetraHydro Box:
-Large 18 gallon storage bin (Wallmart $4)
-Steralyte plastic basket w/ holes (Wallmart 2 for $3)
-2 cubic feet of potting soil (this brand at Lowe's $5, but find it at Home Depot also)
-2 cups of fertilizer (Home Depot $12 for HUGE 15lbs. bag, you can buy way smaller)
-2 cups of garden lime (Home Depot 10 cup bag $3.50)
-About 1 foot of 1 inch pvc each (Home Depot $2.5 for 10 feet)
-6 scrap of any rubber tubing for drain
-Large trash bag

Small TetraHydro Box:
-Small 18 quart dish bin (Wallmart $3)
-Drawer organizer plastic basket w/ holes (Wallmart 2 for $1)
-1/2 cubic foot of potting soil (this brand at Lowe's $2.5 for 1ft, but find it at Home Depot also)
-1 cups of fertilizer (Home Depot $12 for HUGE 15lbs. bag, you can buy way smaller)
-1 cups of garden lime (Home Depot 10 cup bag $3.50)
-About 1 foot of 1 inch pvc each (Home Depot $2.5 for 10 feet)
-6 scrap of any rubber tubing for drain
-Large trash bag

Nothing to specific make sure its large enough and will hold the basket with holes in it upside down. If you don't buy the suggested bin you will have a good understanding of how to pick your own by the end of the guide.
Make sure it fits in your box upside down. you are going to drill holes in the bottom later so it will act as a membrane between dirt and water but allow the roots to penetrate.
Earthbox recommends or more requires that you only use potting MIX... i use SOIL... either is fine... mix just costs more. Earthbox says the difference is that soil contains rocks and mix does not. I have no idea where they came up with that idea. I have never seen a rock in potting soil, and so what if there was a few is it worth double the price? The difference i do know of tho is that potting MIX has already been fertilized and they add perlite. Perhaps that is worth paying double for, i don't know tho. I've used them both in separate boxes simultaneously and noticed no difference.
Earthbox says any fertilizer will work as long as the numbers are 15 or less, as in 5-8-12 or some combination. The one i am using is 16-16-16. I guess I am just defiant... lol :)
-Garden lime
Very hard to find! Strange considering how important it is for gardening tho. Earthbox recommends you use dolomite or hydrated lime. I understand that the lime used for concrete can also be used but may burn plants. The brand I found at home depot was cheap enough and has way more benefits too. The purpose is too raise the soil ph as most vegtables need more acidic soil and also to fortify the soil with calcium. Without your plants may suffer from what is called blossom end rot and it ruins you crop. I have seen it personally years ago and would add the vitamin tablets of calcium or crushed egg shells after ward, but the garden lime i found has tons of other vitamins and minerals too.

Step 3: Begin! Drill Holes

Drill holes all throughout the bottom of your basket I'd say anything between a 1/4" and 3/8" are good... I used a step bit so mine cam out random sizes.

Ignore the etra steps already don on the large one... we'll get there :)

Step 4: Cut PVC, and Bgin Assembly

Cut yur 1" pvc so that it is long enough to reach from the bottom of your box and stick out a few inches. Notch the end if you like to make sure it won't sit flat on the bottom and get clogged.

Next put your basket into your box upside down and cut a corner of the basket to penetrate the pvc through.

Sorry no pic of the large bin because if forgot till i had added some dirt! lol...

Step 5: Drain Hole

It is important to put your drain hole at the top of where your water line should be. So put it at the top of the basket. a simple hole in the side will clog with dirt a little and drain slower so i used a small rubber auto hose to "bring" my drain hole inside the basket as pictured. Try to make the hole in the side the same size as yur drain hose but there is no reason to make it a perfect fit or seal it its a drain! :)

forget the dirt in the small one... lol.. the drain hose was a last minute mod :)

Step 6: DIRT! :)

Fill the box halfway with dirt. to keep as little dirt as possible from entering the resevoir it is better to dump the dirt in fast instead of slow.

For the large boxes the take 1 cubic feet of dirt that means add a whole 1 cubic foot bag right now, and for the smaller boxes it only takes 1/4 cubic foot.

Next, fill the reservoir with water till it starts coming out your drain hole. Then thoroughly soak the dirt down for at least 60 seconds so it is completely drenched throughout. You can even "massage" the dirt a little with your hands to get it to soak in everywhere.

Now add 1/2 the garden lime for the large TetraHydro Box, 1 cup, and all of it for the small box,. also 1 cup.

Next, add the rest of the dirt to top off your box and soak the dirt for another 60 seconds.

Step 7: Fertalizer Strip

For the small TetraHydro Box there is no garden lime left to add, but for the large box and the rest of the garden lime and for both add your strip of fertilizer. Earthbox recommends different arrangements for different plants, but personally i always grow 6 plants with a strip in the middle. They recommend 2 tomato plants but i have grown 6. Usually i like to mix and match tho. Like 4 tomatoes, a pepper and a large leafy plant like squash or cucumber.

In any case... dig your small trench and add all of the fertilizer. Cover the fertilizer again and when you add the plants try not to disturb the fertilizer strip at all.

The Earthbox recommendations are attached as a pic.

Step 8: Add Cover

Stretch a large thick trash bag over as a cover. For the large TetraHydro Boxes this is a little difficult. Once the bag is over tho, poke holes thru so the watering pip can come through and to lay out your plants. Make the holes as small as possible.

Step 9: Add Your Vegatbles! :)

Since the small boxes are more experimental i added 4 tomatoes to one and 6 to the other. We'll see what it can handle. With the large boxes tho I know it can handle 6 tomatoes even so one has 4 tomatoes, an egglplant and a cucumber, and the other has 3 tomatoes, a squash, and a cucumber, with one more spot awaiting a pepper probably :)

Enjoy your veggies! :)

ATTN! If you like this guide please rate it with a 1-5 star rating to the right of this text and leave comments with constructive criticism :) Thanks :)