Introduction: Large Concrete Planter

Full disclosure: This is my first time working with concrete.

That being said, I think my concrete planter turned out pretty great! I really wanted a large round indoor concrete planter, and as usual, couldn't find one for purchase that suited my needs. So I decided to make my own!

You can watch the step-by-step process video or read on for more details!

Step 1: Materials

Start by gathering your tools and materials. For this project you'll need:

Other tools/accessories also used:

Step 2: Add Braces to the Small Bucket

The idea is to use the buckets as your inner and outer form supports to create the concrete planter. In order for the small 2-gallon bucket to float within the larger 5-gallon bucket, I strapped on some wood slats using corner braces.

Recommendation: While I didn't think to do this at the time, I recommend adding spacers (cut some small wood blocks) to your wood slats so the small bucket will sit dead center when placed into the larger bucket. I didn't do this, so my planter walls ended up thicker on one side than the other.

Step 3: Lubricate the Buckets

This is my first time working with concrete, but I've heard it's a good idea to lubricate the forms so that it will be easier to take it apart once the concrete dries. I used canola cooking spray and added it liberally to the inside of the large bucket and outside of the small bucket.

Step 4: Mix the Concrete

There are so many types of concrete to choose from, it can be confusing! I decided to purchased the most basic (and cheapest) 30 Kg bag of concrete available, Quikrete concrete mix. I ended up using maybe 40 lbs.

Simply start with a small quantity of powder and gradually add water, mixing as you go. Stop adding water when your mix looks wet with clumps, sorta like oatmeal.

Tip: Wear a respirator or at least a dust mask so you don't breath in the dust the inevitable airborne concrete dust.

Step 5: Compact the Base

Start by building up the base of the planter by filling the bottom of the large bucket with a few inches of concrete. I used my hands (wearing nitrile gloves) to really push it into the corners and compact it. I also shook the bucket, tapped on the sides, and slammed it down on the ground a few times to help the air bubbles rise to the surface.

Keep building the base, testing as you go, until the bottom of the small bucket sits flush on top of the concrete base.

Step 6: Build Up the Sides

After the base is formed, I started to build up the walls just a few inches high using my hands to place some concrete against the sides of the bucket.

Eventually I pushed the small bucket into place and started filling the sides bit by bit using my trowel.

Once the cavity is full to the desired height (in my case right under the lip of the smaller bucket), again shake, tap, knock and rattle your bucket so the concrete compacts as much as possible and forces the air bubbles up to the surface.

Note: You will need to fill the small bucket with some weights to hold it down. You can use bricks, sand, rocks, etc.

Step 7: Let It Cure

I used some sheathing tape to secure everything into place so it wouldn't shift while drying. It's also a good idea to cover the buckets with a plastic bag while it dries.

The Quikrete bag said the concrete takes 5 days to cure, but I figured since it’s only a flower pot, I could risk taking it out after 2 days. Turns out after 2 days it was still wet, so I waited another 2 days, 4 days total.

Step 8: Remove the Forms

So it turns out the cooking oil trick did not work at all. The buckets were seriously stuck to the concrete, no matter how many times I tried to knock the concrete planter out. So in the end, I ended up cutting both buckets down the side with a utility knife in order to release the planter.

Step 9: Final Result

I used some sandpaper to polish the top of the planter’s lip. The final result looks awesome!

Now all that’s left is to plant my fiddle leaf fig tree in my new concrete flower pot, and now that I look at it, I think it could use a plant stand… which is a great idea for my next post! Click here to check out the DIY Wood Plant Stand Instructable.

If you haven't already done so, you can watch the build video How to Make a Large Concrete Planter
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Comments

author
Daisytikityke (author)2017-08-24

I love the look of your planter, and especially like the uneven thickness of the top!

author
duna6430 (author)2017-08-22

An electric sander (w/out the sandpaper) held on the sides of the bucket might vibrate enough to force out any air as the mix settles. Thanks for the post - great looking planter!

author
BarnatL (author)duna64302017-08-23

Or just gently tap the bucket vith something ritmically if you dont have any of those machines :D !

author
a1jim (author)2017-08-22

I always had a problem using diesel fuel as a release agent for construction work, so I switched to Crisco shortening making sure to apply a fairly heavy coat, it works like a dream with an easy release and an smell like baking bread.

author
oky jim (author)a1jim2017-08-22

as you learned vegetable shortening is an excellent mold release. Margerine works well also but is expensive compared to shortening, but it smells better.

author
danzo321 (author)2017-08-22

The correct oil for concrete casting is called Form Oil, and it's close to diesel fuel, so use that next time. Because the 2 gal bucket has those strength ribs around the top, I would go find something else, like a wastebasket, and we use sand and maybe steel to weight it down. Quikcrete should take overnight to harden, in the summer, so you did something wrong. I would use a piece of sheet metal as a chute to slide wet mix in. Pretty good surface anyway!

author
dk816 (author)danzo3212017-08-22

I have made forms for my house foundation and used form oil. It is smelly and not something you would want to have as a residue on your skin or the final product. Recently I did a couple forms for foundations for additions and used some rancid coconut oil I had... it was a little cool out so I heated it a little to work with it and then is solidified on the forms... worked like a charm! Now, having said that there could be a suction factor as when you try to pill a bucket out of the same size bucket. Split forms are typically used for concrete art forms, there may no way around cutting them off unless you split the buckets first and figure a way to secure them for the pour and then undo and pull away in halves.

author
danzo321 (author)dk8162017-08-22

You know about oil and water? The form oil never shows up on the concrete surface. Maybe it evaporates too. If you were going to make bucket casts a lot, you'd have an air hose nozzle in the bottom and hook up an air hose to pop the casting. Or at least a hole you could block with clay or something, to break the vacuum.
We should also talk about superplasticizer but I don't know if hobbyists can get it in small quantities.

author
Lizmagno (author)2017-08-22

Your Planter is truly beautiful! But I think most plants need drainage to survive. That's why flower pots have a hole in the bottom. You could probably use a concrete drill bit or put corks or something long enough in the bottom layer as you form it. You might also think about making some kind of wheeled Caddy to keep it on if you have to move the plant indoors for the Winter. It can get very heavy once it's filled with soil.

author
ElizabethGreene (author)2017-08-22

Another note on forms: If you can find one that tapers slightly from a fat top to skinny bottom that helps tremendously in removal.

author
nsomnac (author)2017-08-22

Having worked with concrete before, a better way to do this would be to cut the lip off the smaller bucket and turn it upside down inside the larger bucket, such that you are pouring the pot upside down. This method will prevent the smaller pot from floating like a boat.

Since this is also just a pot, you could use a slightly soupier mix (consistency of a milkshake) as we aren't too worried about the strength of the concrete. Also if you have access to a concrete vibrator, you could use it along the sides of the formwork to remove air pockets in the walls of the pot.

Also for a pot, you might also consider adding a piece of pvc into the bottom for a drainage hole to prevent root rot from over watered soil.

author
MelissaM242 (author)2017-08-22

I made an outdoor one using corks to keep spaces open in the bottom (then drilling them out) a few years ago. Looks great. Only problem is it weighs 65lbs!!

author
GeorgeD36 (author)2017-08-22

Hi Mary,

Great Instructable thanks, very clear. Nice looking planter.

I made a range similar planters to those you did but square. To get different sizes I used cardboard boxes (mostly ex Amazon) and cut them down to make the inner and outter sizes for each mould.

To prevent the cardboard from collapsing I lined the faces with cheap packing tape. Otherwise the method was exactly as you describe.

The resulting planters are very strong and durable.

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author
DavidS925 (author)2017-08-22

Motor Oil works when using wooden forms. But I doubt it would adhere to the plastic well enough.

author
franka95 (author)2017-08-22

great job!

I wonder if vaseline or petroleum jelly would act as a good release agent.

I saw something about Smooth-On’s AquaCon®, and they also say it works, but may stain the concrete... I dunno..

author
seamster (author)2017-08-21

Very cool. I need to make a couple of these. Thank you for the instructions!

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