Introduction: Cemented Carnivorous Cannibalistic Planter


We are huge fans of carnivorous plants and how they have evolved to capture prey in nitrogen-limiting conditions, but also their ability to sense what is true prey and what is a false alarm.

We are also a fan of Plants vs Zombies so combined our venus fly trap with Chomper from Plants vs Zombies to make carnivorous cannibalism.


  • 3D printer (We used the Anycubic I3 Mega)
  • PLA filament
  • Portland cement
  • Cutting Snips
  • Acrylic paints and brushes
  • Vasoline
  • Gloves
  • Hot glue gun or glue sticks and a lighter
  • Epoxy Glue
  • Masking tape
  • Plasti-Dip Spray
  • Spagmoss or other appropriate Venus Fly Trap grow-medium
  • Distilled Water
  • A venus flytrap or another preferred plant

Step 1: Designing the Planter

When designing it is important to sketch drawings of what you roughly want your model to look like. This ensures that you cover all the practicality of it before you do a 3D design. Since this model uses a 3D printer and an embedded venus fly trap planter it was important we get the right dimensions so it fitted on the print bed without having to print it in parts.

Here are a few of our concept sketches.

Step 2: Modelling the Planter in 3D

After we were happy with a concept we designed our model in Blender version 2.79, an open source free CAD program. If you haven't heard of it, we highly recommend you check it out! However that is beyond the scope of this Instructable. Download Blender here:

Step 3: Modelling the Planter Moulds

Using the 3D model in the previous step we make solid cases around the models and took the boolean difference of the models. This hollows out a mould.

Step 4: Printing the Planter Moulds

We used the ANYCUBIC I3 MEGA printer with 1.75 mm PLA filament to print the moulds for the planter. We used bright colours that we don't use frequently as the moulds take up a lot of filament and are destroyed afterwards. The moulds took approximately 40 hours total to print and used about 800 grams of filament.

Once the mould is printed you need to remove the supports inside the the head of the plant.

Ensure the surface is smooth before adding the cement otherwise you may end up with with weird mould marks in your model after you de-mould it. Use snips to clear out any support.

Step 5: Assembling and Prepping the Mould for Cement

To make the model both easier to remove and sturdy during cement addition we had to prep the mould.


  • The vasoline coating makes demoulding a bit easier as the cement is less likely to stick to the plastic during removal.
  • We smeared a layer of vasoline in the inside of each of the moulds

Assembling the moulds

  • Pot - We used hot glue on the bottom of the pot to adhere the inner mould to the bottom. To ensure it was stable we used masking tape around the complete pot for stability.
  • Plant head - The plant head was made in two pieces so we taped them together with masking tape tightly to ensure no gaps where the cement could escape.
  • Leafs - Mould is only one piece so no assembly is required.
  • Spikes - Mould is only one piece so no assembly is required.

Step 6: Filling the Moulds

Health and Safety

Cement in its powder form contains crystalline silica prolonged or repeated exposure can lead to health complications. Please use gloves when dealing with cement and use in a well-ventilated area with dust masks if you can.

Do not tip any cement powder down drains as it can clog when dry. We disposed of any gloves and newspaper in the rubbish bin.


We used a 2:1 ratio of water to cement, in cups. However, you just need to make sure that no lumps are present and the consistency of the cement is smooth but not a liquid. The more liquid it is the greater the chance for cracks to form.

Gently pour or scrape the cement into the moulds until they are full. To ensure we had no air gaps we used a wooden kebab skewer to poke into the cement and then applied more cement as required.

The cement caused the insert of the pot to become buoyant so we used a brick to sit on top of the insert while the cement dried.

Moulds to fill

  • Head mould
  • Pot mould
  • Leaf mould
  • Spike mould

Tips and tricks

  • Cement with a high water-content will flow easily into all the corners of the mould but will cause the cement to crack more easily. Our cement was probably a bit too watery so we did get a crack. Aim for a "pancake batter" consistency.
  • Shaking the mould of cement with high frequency oscillations will cause liquefaction to occur (the solid particles move over each other in the water). This will make the cement flow into the corners of the moulds.
  • Use a kebab skewer to stab the cement in the mould and get out any air bubbles.

Step 7: Removing the Concrete

The cement was left to dry for at least 48 hours before we removal.

As expected, removal of the moulds from the cement was not easy and make sure you have a few hours of time on your hands as well as a place to put the tiny pieces of plastic flaked off cement.

A few recommendations:

  • Wear gloves to prevent cuts from the plastic
  • Use snips to pull of large chunks of plastic rather than cutting through it
  • Take your time and be patient and careful it is easy to slip and stab your hand into the plastic or the snips.
  • Try and lever any plastic off the mould, often the plastic will snap in a nice big chunk (but try not to crack the fragile cement!)

Step 8: Adding the Spikes and Teeth

Demould the spikes and teeth gently from the plastic, the tips were very thin so frequently chipped off however we just filed these so they were slightly rounded and glued any of the major chips.

To glue them to the concrete we mixed and epoxy glue and applied this to the base of the spike or the tooth. Any excess glue we wiped off with a paper towel then left it propped up (on a peanut butter jar) and left them 10 minutes to dry, and overnight to fully dry.

Step 9: Fixing the Gaps in the Concrete

Since our model had a few casting flaws around the neck we used additional concrete as a filler and left to dry for 24 hours.

Step 10: Making the Planter Safe for Venus Fly Traps

Cement is toxic to venus flytraps! It can leech into the Sphagnum moss the plant resides in causing damage to the roots! generally, it is recommended to use plastic or polystyrene pots. However, since we wanted a nice heavy solid pot and did use cement it was important we made it safe for the plant. After some research, we came across Plasti-Dip, an aerosol that makes a rubber coating. We even managed to find another carnivorous plant enthusiast who uses Plasti-Dip on their pots.

To apply:

  • Wipe the surface to remove any loose pieces of cement.
  • Shake the can for a minute, shake often while applying also.
  • Hold the can 12"-16" away from the surface.
  • While spraying move the can back and forth slightly overlapping each stroke.
  • Spray enough so that it shows up wet
  • Allow 30 minutes of drying time between each coat (We used ~8 coats for the inside and 4 coats for the bottom).
  • Allow 4 hours for complete drying time.

For the base, we used tape and toilet paper to make a ~1.5cm rim so that water can be applied to the bottom without concrete minerals leaching into the medium.

We also used the Plasti-dip inside the neck of the planter head as the fly traps would be touching that area.

Step 11: Adding the Leaves

Unfortunately, while removing the leaves from the 3D printed mould they broke into pieces. We were roughly able to glue them back together roughly then used additional cement as a smoother to make them sturdy and smooth looking.

We suggest using an aggregate such as sand or gravel with the cement to make it less brittle or adding wire to make a frame.

Step 12: Painting the Planter

We used a deep purple as the base coat for the head of the planter. Followed by three lighter coats of purple.

Apply 2-3 coats of lime green acrylic paint for the lips.

Mix red paint with some black and a small amount of yellow to make a deep red, resembling the inside of the mouth. We used a wide brush most the mouth and a small one for around the teeth and lips. At least two coats are required.

Apply at least two coats of white paint to make the teeth stand out.

To make the gradient of yellow to white we applied a straight yellow dry brush (most of the paint rubbed off the bristles) to the base of the tooth while the white was still wet and blended it slightly down the tooth. To limit the brush strokes on the teeth we used our finger to smooth it gently.

Apply at least two coats of lime green to the three spikes, make sure it is lighter than the lips. We added some white to make this colour.

Again, to make the gradient we used a small amount of dark green for the base of the spike and blended it with the lighter green.

Make a very dark purple paint (mostly blue and a little bit of red) apply this as spots to the head of the planter. We used two coats for this layer.

We used a dark green base coat and a slightly lighter green topcoat, make sure it is a different shade from the lips. We made the veins using a lighter green and painting them freehand on the front of the leaves.

Apply two coats of dark grey/charcoal to the outside of the pot using a wide bristle brush. Avoid painting over the Plasti-dip coats.

Step 13: Adding the Venus Fly Trap

We used Spagmoss to fill up the plant pot.

First, we hydrated it with ultra distilled water and squeezed the remaining water out before packing it gently into the pot.

We gently scooped out the venus fly trap from the plastic container and placed it into the new planter.

Finally, we packed some additional Spagmoss and the remains of its medium from the pot into the planter.

And voilà you have a Cemented Carnivorous Cannibalistic Planter!

Stone Concrete and Cement Contest

Runner Up in the
Stone Concrete and Cement Contest