Introduction: Geometric, Pentagonal Planter From Cardboard and a Plastic Bottle

About: I am a potter, painter, gardener, woodworker, and a whole lot more! I love learning new skills and putting them to use on all kinds of creative projects!

Hello everyone! This is my first instructable and my entry into the indoor plants speed challenge! Today, I’m going to walk you through my process for making a really neat planter out of cardboard and plastic bottles.

I love playing with geometric forms and shapes. Seeing the ways they interact with each other and all of the fascinating things they can do is just amazing and I really enjoy drawing, making, and creating with them.

I also wanted to plant a lot of plants indoors but didn’t really want to spend a lot of money (and planters can cost a LOT of money, especially geometric ones). You probably already have all of the tools and materials we’ll use right in your own house.

Last but not least, I wanted to use some materials that would otherwise be going straight to the garbage. It feels good to reuse materials that are otherwise considered trash and I wanted to do that with this project.

So without further ado, let’s get started!


For this instructable, you will need:

- Cardboard (the bigger the pieces, the better)
- A plastic bottle (I used a gallon milk jug and it works great)
- Duct tape
- *Optional* Clear silicone caulk, glue, or other adhesive or sealant
- *Optional* Polyurethane, paint, or some other kind of decorative finish

- A sharp utility knife (be careful, it’s sharp)
- A ruler or straight edge
- A drawing compass or protractor
- A pen or pencil
- A surface to cut on
- *Optional* A caulk gun or ziploc bag for piping silicone sealant

Step 1: Pick Your Planter’s Size and Choose a Container

For this step, choose the size of container you would like to use for your planter. Bigger containers will obviously allow for bigger plants while smaller ones will be more suitable for small ones. The size of your container will also determine the finished size of your planter.

Once you’ve chosen the bottle for your container, cut it in half and then insert the top half of the bottle into the the bottom half. This creates a natural draining system that will keep your little plant babies happy!

Step 2: Determine the Size of the Planter’s Base

Measure your bottle container by placing a compass in the middle and finding the edge that is the furthest away from the middle. This will determine how wide the base of you’re planter needs to be.

Pro tip: I always add half about half an inch to the just to make sure I have enough room.

Keep the compass set up this way and move on to step three!

Step 3: Choose the Planter’s Shape and Create a Template

Ok, this is by far the most difficult step of this instructable. Please don’t give up on me! I promise it will get way easier after this.

These can be made in all kinds of shapes but I’m going to show you how to make a pentagonal shape. I’ll walk you through the steps I use, but there are many ways to make a regular pentagon. There’s even a great instructable on it here: ( You can also just do a search for a pentagon, print it off and use that as your template. If you have your own way of making a pentagon, go ahead on to the next step. Otherwise, keep reading and I’ll show you mine!

To make a pentagon, first, take your drawing compass and make a circle on your cardboard in the size you established in step two. This establishes the size of your pentagon.

Next, draw perpendicular lines at the center of your circle as shown.

Place your compass on the furthest line to the left and draw another circle the same size as before. You should now have two intersecting circles.

Using your straight edge, make a line from the point where the tops of the two circles meet to where the bottoms of the two circles meet.

Place your compass where the new line crosses the midline of the old circle.

Adjust your compass so it meets the top point of the original circle.

Draw an arc that crosses the other half of the midline.

Expand your compass so that one end is at the Mark you just made (where the arc crosses the midline) and the other end is at the very top of the circle.

Draw with your compass toward the outer edge of the circle.

Move the point of your compass to the point that identifies where the new line and your circle meet.

Following the circle, make a hash line, giving you a mark.

Congratulations! You’ve just created five equidistant points! Now, just use your straight edge and your pencil or pen and connect your points by drawing lines between them.

Cut out your pentagon template.

Phew! That was a LOT. Let’s move on to something easier.

Step 4: Trace Pentagons for the Sides of the Planter

Using the template we just created, make six new pentagon tracings on your cardboard.

Pro tip: keep the pentagons connected where possible. This will keep you from having to tape so much and will make for a cleaner, stronger finished product.

Also be sure to trace on the side you want to hide on the inside of the planter to keep the imperfections of the cardboard out of sight.

Step 5: Create Triangles to Fit Your Pentagons and Cut It All Out

Take the pentagon template and cut off the top triangle (the area above the two furthest possible points on the pentagon). Trace five of these on your cardboard, lining them up with the tops of the pentagons as shown. Doing it this way will make it possible to fold it all up in one piece, saving a lot of time and tape.

Cut out your traced shape or shapes.

Step 6: Scoring and Taping

Lay out the shapes you just cut out and score the lines between the sides, being careful not to cut all the way through. Begin folding and taping the sides together until they form a bowl-like shape.

Tape your triangles together to the top of the pentagons, making one complete piece.

Step 7: Make the Top

Flip your pentagon/triangle bowl over and trace the rim to create the top. Make a circle in the middle that is big enough to fit your plant container through.

Cut out the top and the circle inside of it.

Tape the top onto the base.

Step 8: Seal the Seams

At this point, you are effectively done! If you want to be that is. Congratulations! You have made an awesome planter! If you want to make it a little more deluxe, though, keep reading!

To seal the seams, put a bead of silicone caulk or another sealer on the exposed edges of your planter. I find it easier to put silicone in a plastic bag and cut the tip as if I were piping icing. I also like to use silicone since it’s waterproof and also readily available.

Step 9: Apply Finish

Once the silicone is dry, apply your chosen finish. I like polyurethane because it lets the natural cardboard show, but it also makes it waterproof and a bit stronger. You might try paint, markers, or even stain.

Step 10: Enjoy!

Hooray! We’re all done! Now all that’s left is to choose a plant, fill the container with dirt, pot the plant, and put it in the planter! I spruce mine up with some cord so I can hang them in my windows, but there are all kinds of ways to enjoy them.

There are also a lot of different ways to make them. Different shapes will have different results and all kinds of fascinating things can happen. Get creative and see what you come up with!

Thanks for reading, making, and imagining! I hope you enjoy your planters and your plants!

Indoor Plants Challenge

First Prize in the
Indoor Plants Challenge