DIY Concrete Planters: How to Make Modern Geometric Pots at Home

Concrete planters have become one of the most popular home decor trends in recent years. Their weight, texture, and raw industrial aesthetic suit both modern minimalist and bohemian interiors. Commercial concrete pots can be expensive, but making your own at home requires only a few dollars’ worth of materials and an afternoon of work. This guide covers everything from mixing the concrete to creating geometric shapes and applying a smooth finish.

Why Make Your Own Concrete Planters?

A single medium-sized concrete planter from a garden centre or homewares store can cost $40 to $120. Making an equivalent pot at home costs approximately $5 to $10 in materials. More importantly, you can control the exact shape, size, colour, and texture to match your decor.

Types of Concrete Mix

Not all concrete mixes are suitable for planters. You need a mix that is strong enough to hold its shape but workable enough to fill a mould smoothly. Three options are widely used by crafters:

• Hypertufa mix: Portland cement + peat moss + perlite (or vermiculite). Lightweight, porous, and looks more like aged stone. Best for outdoor planters.
• Ready-mix concrete: Available from hardware stores. Fast and convenient. Creates a heavier, denser pot. Fine aggregate mixes (without large stones) are better for smaller moulds.
• Cement and sand mix: 1 part Portland cement to 2 parts fine sand, mixed with water. This is the classic DIY planter recipe and gives excellent results for smooth geometric shapes.

Materials You Will Need

• Portland cement or ready-mix concrete (fine aggregate)
• Sand (for cement-and-sand method)
• Water
• Plastic or cardboard moulds (two sizes: outer mould and inner mould)
• Cooking oil or petroleum jelly (mould release agent)
• Mixing bucket
• Old spoon or trowel
• Rubber gloves (cement is caustic – protect your hands)
• Safety glasses
• Sandpaper (120 and 240 grit)
• Sealer (optional: concrete sealer or polyurethane)

Choosing Moulds for Geometric Shapes

The most popular geometric shapes for concrete planters are cylinders, cubes, and hexagons. Your moulds can be:

• Cylinder: Two round plastic containers of different sizes (yoghurt pots, takeaway containers, mixing bowls).
• Cube: Two cardboard boxes of different sizes, lined with cling wrap for waterproofing.
• Hexagon: More advanced. Construct from cardboard panels cut to equal dimensions and taped together.

The gap between your inner and outer mould is the thickness of your planter walls. Aim for 2.5 to 3cm for strength and durability.

Mixing the Concrete

1. Add 2 parts fine sand to your mixing bucket.
2. Add 1 part Portland cement and mix the dry materials together thoroughly.
3. Add water gradually. Stir constantly. You want the consistency of thick peanut butter – it holds its shape but is pliable enough to work with. Too wet and the pot will crack; too dry and it will be difficult to fill the mould without voids.
4. If you want coloured concrete, add concrete pigment powder to the dry mix before adding water.

Filling the Mould

1. Coat the inside of your outer mould and the outside of your inner mould thoroughly with cooking oil or petroleum jelly. This is your mould release and is critical for removing the set concrete.
2. Add a layer of concrete to the bottom of the outer mould, approximately 3cm deep. This forms the base of your planter.
3. Press a small pebble or a piece of dowel into the base concrete to create a drainage hole. Remove after the concrete sets.
4. Place your inner mould centrally on top of the base concrete.
5. Fill the gap between the inner and outer mould with concrete, tamping it down with a pencil or stick to eliminate air voids.
6. Smooth the top surface with a wet finger or spoon.

Curing and Demoulding

1. Cover the mould with a plastic bag to slow the curing process. Concrete gains strength through chemical hydration, not drying, so keeping it moist is important.
2. Leave to cure for a minimum of 24 hours before demoulding. 48 hours is better for small pots.
3. Carefully remove the outer mould first. Cardboard can be torn away. Plastic containers may require a firm tap and twist.
4. Remove the inner mould. Squeeze flexible plastic containers to break the seal. For ridged containers, use a knife to cut them away carefully.
5. Allow the pot to continue curing fully uncovered for a further 24 to 48 hours before planting.

Finishing Your Concrete Planter

Wet concrete is rough and porous. Sand it with 120-grit sandpaper, then 240-grit for a smoother texture. Wipe clean with a damp cloth. For an ultra-smooth finish, apply a skim coat of cement paste (neat Portland cement mixed with just enough water to form a paste) over the surface and sand again when dry. Apply a concrete sealer to protect the planter from moisture and frost if it will live outdoors.

Pair your concrete planter with terrarium-style plantings – see our DIY Terrarium guide for plant selection ideas. Browse our full Home Decor category for more DIY projects.