[Update April 2019]: Just about to start our third season, and these planters are holding up really well! The wheels still roll smoothly, and no rust so far.
Want to make cool galvanized trough planters? So did I! Here’s how I did it.
Why galvanized trough planters?
Lots of reasons.
We live in an old house, and old houses tend to have lead in the soil. The nice folks at UMass tested our soil and confirmed it does, in fact, have lead. So we can’t have a normal garden in the ground.
Last year, we tried straw bale gardening. It was great, but some plants (namely basil, carrots, cabbage, a few others) did terribly in the bales.
Mrs. MakerJosh grew up with horses, and always liked the look of galvanized metal water troughs. Good old Pinterest showed us lots of ways it could be done, but no specific instructions for how to do it.
This spring, we decided to take the leap. I was going to build six galvanized trough planters. Our garden would be half galvanized trough planters, half straw bales.
The finished galvanized trough planters
Before we dive in, take a look at these beauties.
About the project
Is it hard?
You’ll break a sweat. It’s not hard, but you’re moving around a lot. You’ll need basic carpentry skills. It’s mostly drilling and screwing (#thatswhatshesaid), so you’ll need a great drill.
Will it hurt?
How long will it take?
If you’re an idiot like me, one planter will take five hours. That includes three trips to the local hardware store.
If you’re not an idiot or if you follow these instructions, each planter will take 30-45 minutes to build.
How much do they cost?
$172 per planter. Detailed cost breakdown at the end.
Galvanized Trough Planter Supplies
1) Galvanized Troughs
They’re called all different things. Is this regional? “Feed troughs,” “food troughs,” “galvanized troughs,” “watering troughs,” “stock tanks,” etc.
We tried to find a used one on our local Craigslist site, but didn’t have any luck. That’s definitely going to be your cheapest option. So start there, and try all the different name combinations above.
After striking out on used, we started looking for new. The two best sources we found were:
For the troughs that we wanted, the prices were about the same between Amazon and TSC. Since we get free delivery from Amazon and we didn’t want to rent a trailer, Amazon was the clear winner!
We ended up getting these “galvanized stock tanks” in the 90-gallon size. Pick whichever size suits your fancy.
They took about a week to arrive. They shipped via freight instead of the typical Amazon Prime UPS/Fedex. That meant we had to be home to sign for them when they arrived.
Trust me, you’re going to want wheels on these things. More on this later, but each planter was easily at least 300 pounds. If you fill the whole thing with potting soil, expect it to be over 600 pounds. They are BEASTS. If you don’t put wheels on them before filling them with soil, you’re not going to be moving them.
There’s another good reason to have wheels — drainage. If you over-water or if it rains, you won’t drown your plants since the planter is a couple of inches off the ground.
I spent a lot of time researching wheels that could handle the load and that would hold up outside. I ended up going with these:
Here’s what I looked for in wheels:
- Ability to hold at least 800 pounds for a pack of four.
- A locking switch so the galvanized trough planters wouldn’t roll around.
- I would have preferred stainless steel or galvanized wheels. These were tough to find. My hope is that they wouldn’t rust too badly since they’ll be under the watering trough.
3) Bolts (size DOES matter)
I’ll be honest — I picked the wrong bolts. And that messed me up, bigly. Trial and error with bolts is the main reason the first planter took five hours.
Here’s the embarrassing evidence of my trial and error:
Here’s where you get to learn from my mistakes. You’re welcome.
First, I got bolts that we were too skinny. They bent, stripped, and generally made life miserable. Don’t go with anything smaller than ¼”. I ended up with ¼”-20.
(LPT: want to know what numbers like ¼”-20 means? Here’s a good article.)
Next, I got bolts that were too long. I guessed that i needed 2” bolts, and had a grand ol’ time attaching that first wheel. It was a delightful surprise when I learned that the bolts were so long that the wheels wouldn’t turn.
So I pulled out my handy folding jab saw and cut the bolts off, and started over.
Last, I got the wrong metal. I know better. But I was in a rush. Zinc rusts. Stainless steel doesn’t. You need stainless steel.
So here’s what you want to use:
- ¼”-20 x 1-½” Stainless Steel Hex Head Bolts. Any longer than 1-½”, they’ll hit the wheels. Anything shorter, they won’t make it out the other side. You’ll need 16 per planter.
- ¼”-20 Stainless Nylon Insert Lock Nuts. Lock nuts are nice because they won’t come loose after they’re attached. Again, 16 per planter.
- ¼” Flat Washers. You’ll need 32 per planter — one for the top of the bolt and one for the nut.
4) Other stuff
Pressure Treated Wood
The bottom of the galvanized trough planters are way too flimsy to support 800 pounds.
I was lucky because I had some wood leftover from a fencing project. I found that the wood commonly used on decks (5/4” by 6”) was perfect. You’ll need 36” (three feet) for each planter.
You’ll also need a roll of this stuff to make sure your potting mix doesn’t just wash away.
The Right Tools
There is no way I could have done this project without these tools:
- An excellent drill/driver. I recently upgraded to this puppy and it’s the best drill I’ve ever owned.
- Some sharp drill bits. You’ll be using the ¼” bit a lot. I also picked up this little kit, and am very happy with the quality.
- Oh my god you need this. I didn’t have the right size when I started the project. I picked one up on one of my trips to the hardware store, and it made things go so much more smoothly. These little adapters let me use a socket wrench on my drill.
- Good safety glasses and gloves. Definitely some sharp metal and wood flying around.
- A good tape measure. I have a few of these kicking around, love the ability for the tape to stand out unsupported.
- Tape to act as a second pair of hands. This is another trick I learned along the way. This Gorilla Tape was great because the troughs were a bit damp. This kind of tape actually thrives in slightly damp situations.
- A good socket set. For this project, it helps to have sockets that are a bit long, like this one.
Let’s get to building the galvanized trough planters!
Planter #1 took me 5+ hours. Planter #3 took me 31 minutes. YMMV.
Step 1: Gather your things
If you ordered more than one watering trough, they will come nested like this:
We thought it was odd that the troughs are slightly different sizes. Once they’re unpacked, though, we didn’t notice it at all.
Your wheels will come in tidy boxes like this:
Step 2: Cut and place your wood
Cut two 18” lengths of pressure treated wood.
Step 3: Unpack your wheels, rough layout
Place your wood and wheels in their approximate spots.
You want the wood as far as possible to the outside edge, with the corners lining up with the edge of the planter. Do this for two reasons: (1) to maximize stability and (2) so that you can reach the wheel locks with your foot.
Step 4: Mark your wheel placement
Measure 1 inch from each end of the boards to find where you’ll mount your wheels.
Step 5: Get to drilling!
Re-position your board so that the corners line up with the edges of the watering trough. Put a lot of weight on the board to hold it in place, then grab your ¼” drill bit and start drilling holes.
(LPT: go slow! You’re drilling through an inch of wood and then metal. If you’re putting the right amount of pressure on your drill, it should take 10-15 seconds for each hole).
Once you’re done with a hole, drop one of your bolts into it. That will keep it in place as you drill the other holes.
Keep drilling holes and dropping in bolts until you finish a side, like this:
Step 6: Flip the trough over (flip 1)
Take the boards off, leaving the bolts in them, and place them to the sides of the planter.
Be careful to keep them oriented in the same direction as they were when on the planter, so that your holes will line up.
Stack up a couple of your boards to raise one end of the trough off the floor. You’re going to need some room underneath for the bolts.
Step 7: Insert the bolts
Put two bolts in each side (don’t try to do all four at once — they’re actually really hard to line up). Put a washer under each bolt head.
Then cover them with a strip of tape to hold them in place.
You’ll end up with this:
Step 8: Flip the trough over (flip 2)
Carefully flip your watering trough back over. You’ll be greeted with four friendly waving arms.
Line up your board over the bolts, and then set two of the wheels on top.
Here’s where this tool really earns its keep:
Put washers and nuts on each bolt end and hand tighten. Then grab your drill and socket combo, and tighten those puppies down.
You want to be careful to tighten these just enough. Too much, and you’ll pull through the thin metal and the bolts will block the wheels from turning. Too little, and you’ll have wobbly galva trough planters.
Using my trusty carpenter’s folding rule, I found that having the bolt end stick out about 3/16” from the nut was perfect.
Step 9: Flip, flip, Flip-a-delphia (flip 3)
Flip your trough over again.
When you do, it’s likely that you’ll see something like this:
No worries! Just grab your drill and ¼” drill bit and re-drill the wood hole.
Then repeat the process, adding the other four bolts to the holes (with a washer on each one!), and taping them down.
Step 10: Flip it again (flip 4)
Flip your trough over again. Put washers and nuts on the remaining bolt ends, and tighten them down.
You’re now the proud owner of a half-made galvanized trough planter!
If you look inside your planter, the bolt heads should be nice and snug up against the metal. If they’re not, you may need to loosen and tighten the nuts a couple of times to draw them in.
Step 11: Rinse and repeat (flips 5, 6, 7, and 8)
You’re now going to repeat the same process on the other side:
- Rough layout of wood and wheels
- Measure 1” from the end of the board, place your wheel, and mark your holes
- Hold tight, drill slowly, dropping bolts in as you go
- Remove the boards and bolts, flip the trough over
- Pop in four bolts and washers, tape them down
- Flip the trough over, and attach two wheels with nuts and washers
- Flip the trough back over, redrill your holes, then pop in four more bolts with washers
- Flip the trough back over and put on the final nuts and washers
Step 12: Drainage
Fantastic! You should now have a galvanized trough planter that’s nearly ready for the great outdoors.
There are still a couple of things you need to do, though — it’s drainage time.
First, drill 10 holes in the bottom of the planter with your ¼” bit. Just randomly space them out.
Finally, unscrew the water plug that ships with the galvanized trough. That’s a perfect use for channel lock pliers, a plumbing workhorse in my toolbox:
Now we’re ready to head outside!
Step 13: Fill the bottom of the planter
As mentioned above, these suckers are HEAVY.
Here’s how much I weighed when I was holding a 50 quart bag of potting mix:
Here’s how much I weighed without holding anything:
(don’t worry – I’m 7 foot 4 inches. That’s a perfectly healthy weight, I’m really not overweight at all).
Each bag was about 60 pounds. It would take 6-8 bags to fill a galvanized trough planter all the way up. That’s 360 – 480 pounds, not to mention the weight of the trough itself.
This would also be a huge waste of money, as vegetable roots don’t go down two feet. Gardener’s Supply has a great summary of how much soil you need for each type of plant:
So we could get by with soil in just half of the trough.
But what to fill the bottom with?
I was in the middle of a dump run when struck with inspiration. I saw multiple people wrestling with packing styrofoam. Not those annoying peanuts, but big stable chunks of styrofoam that can pad a TV.
10 minutes later, I was the proud owner of lots of free styrofoam. I was also the subject of five people looking at me like I was crazy when I told them that I’d take their styrofoam.
I broke up the styrofoam and placed it in the bottom third of the planter, careful not to cover the drainage holes.
I made sure I had about 18” left for soil.
Then I covered the styrofoam with landscape fabric. This will keep the soil from washing away.
Step 14: Fill ‘er up
It’s time to fill it up.
I forked in a few forks of partially-composted straw (from last year’s straw bale garden):
Then I filled the remaining space up with potting soil, leaving an inch or two at the top. It took 3-½ 50 qt. bags of potting mix to fill up top of each galvanized trough planter.
Here they are, all ready for planting!
Chemicals and Organics
As a family, we always try our best to eat organic produce. We definitely had some thoughtful moments during this project.
Is it safe to grow in galvanized metal?
This article from Rodale Organic helped me grok the risks of growing food in metal. Specifically, this quote:
“Due to zinc’s limited bioavailability in soil, there is little chance of ingesting too much zinc through plants grown in proximity to galvanized metal”
We thought for a moment about plastic liners like these, but is plastic really better than metal?
Yeah. We had the same thought. We didn’t find any definitive studies or articles on the topic, but decided that having them in the bottom and having landscaping liner between the soil and the styrofoam made this a low risk situation. If you know something different, please post it in the comments!
Organic Potting Mix
Doh! We would have preferred organic potting mix, but the local home improvement store was out of stock. It’s back in stock now, though, and the price is similar.
Detailed Cost Breakdown
Here’s what we paid for six planters (prices from March 2017):
- Six galvanized stock tanks: $564
- Six 4-packs of wheels: going with these: $162
- One roll of landscape fabric: $23
- A box of 100 ¼”-20 x 1-½” Stainless Steel Hex Head Bolts: $22
- A box of 100 ¼”-20 Stainless Nylon Insert Lock Nuts: $13
- Two boxes of 100 ¼” Flat Stainless Steel Washers: $12
- 15 50 qt. bags of potting mix: $217
- 3 pressure treated 8’ x 5/4” x 6” boards: $19
- Styrofoam from the dump: FREE with strange looks!
Total for SIX: $1,032
Cost for one planter: $172
If you’re looking to cut costs on this project, here are a few ideas:
- The biggest expense is the planters. Use an IFTTT recipe to get emails whenever someone posts something on Craigslist that matches search phrases like watering trough, feed trough, stock tank, etc.
- Watch for sales on potting mix / potting soil. That’s the next biggest expense in this project. Don’t use regular old garden soil — it’ll be even heavier and you’ll have drainage problems.
- I suppose you could skip the wheels, and just rest the planters on bricks or stacked wood. I wouldn’t recommend it, though — you’ll be fine the first year, but in a world of hurt from year 2 and on.
What do you think?
Have some ideas of how I could improve the design? Have questions, or pictures of your own planters that you want to share? Put them in the comments below!
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