If you are looking for a reliable pot sizing guide to stop you from buying the wrong size planter, you have come to the right place. We have all been there—standing in the nursery, holding a stunning Fiddle Leaf Fig, and scanning the aisles for a pot that looks “about right,” only to get home and realize it doesn’t fit.

When you try to slide that nursery bag into your new decorative pot, disaster strikes. It’s either a squeeze so tight you need the jaws of life to remove it, or it’s swimming in so much empty space that it looks like a child wearing their dad’s blazer.

It is a common struggle. At Potanical, we believe that a pot isn’t just a container; it is the furniture for your plant. And just like a good suit, the fit needs to be perfect.

Here is your essential pot sizing guide to getting that designer look while keeping your plants happy and thriving.

The Golden Rule: The “Cover Pot” Method

Before we dive into the numbers of this pot sizing guide, we need to talk strategy.

In the world of professional interior landscaping, we rarely plant directly into the decorative pot immediately. Instead, we use the Cover Pot Method. This means keeping your plant in its plastic nursery grow pot and simply sliding the whole thing inside a beautiful Potanical vessel.

Why do we love this method?

1. Drainage is easier: You can lift the plant out to water it in the sink or shower, ensuring it never sits in stagnant water (the #1 killer of indoor plants).

2. Flexibility: Want to swap your Monstera from a Steel Planter to an Earthly pot? It takes five seconds.

3. Mess-Free: No potting soil on your Persian rug.

However, for this to work, the sizing has to be precise.

The 2-3cm Rule (For Small to Medium Plants)

When you are shopping on our online store, you will see dimensions listed for every pot. But how does that translate to the plastic tub your plant is currently living in?

A general rule of thumb for any pot sizing guide regarding table-top plants and small floor plants (up to 1 metre tall) is the 2-3cm Rule.

Your decorative pot’s internal diameter should be 2 to 3 centimetres wider than the diameter of the plant’s nursery pot.

• If your plant is in a 15cm nursery pot: Look for a decorative pot with an opening of 17cm – 19cm.

• Why? This gap allows you to easily slip your fingers in to lift the plant out. It also provides enough air circulation around the roots to prevent mold build-up, without leaving a gaping hole that ruins the aesthetic.

The 5-7cm Rule (For Large Statement Trees)

When you graduate to the big leagues—we are talking 2-metre tall palms or Strelitzias—the pot sizing guide rules change slightly.

For these larger root balls (usually in 25cm+ nursery bags), you need more breathing room. Aim for a decorative pot that is 5 to 7 centimetres wider than the grow pot.

Large plants are heavy. You won’t be lifting them out to water them often. The extra space allows you to place a substantial drip tray inside the decorative pot at the bottom. It also gives you room to add a layer of decorative pebbles or moss on top to hide the plastic rim, creating that seamless “planted” look.

Quick Reference Pot Sizing Guide Cheat Sheet

To make your life easier, bookmark this pot sizing guide cheat sheet for your next Potanical haul:

Browse our full range of Indoor Pots to find these sizes.

Depth Matters: Don’t Ignore the Height

We often get so fixated on the width that we forget the height. An accurate pot sizing guide must consider the vertical fit as well. There is nothing worse than a plastic nursery rim sticking out 3cm above the edge of your gorgeous designer pot.

The “Shoulder” Test:

Ideally, the rim of your nursery pot should sit about 1-2cm below the rim of the decorative pot. This creates a shadow line that hides the plastic.

If your decorative pot is too deep (which is common with our elegant, tall designs), do not panic. You do not need to fill the bottom with expensive soil. simply place an inverted plastic saucer, a brick, or even a layer of styrofoam at the bottom of the pot to act as a “riser.” This lifts your plant to the perfect display height.

Proportion and Aesthetics: The “Thirds” Concept

Size isn’t just about physics; it is about fashion.

Interior designers often use the Rule of Thirds. Visually, the pot should take up roughly one-third of the total height of the arrangement, while the plant takes up the top two-thirds.

• Too Top Heavy: A giant bushy tree in a tiny, narrow pot looks unstable and anxious.

• Too Bottom Heavy: A tiny succulent in a massive urn looks lost.

However, rules are made to be broken. A low, wide bowl planter with a tall, architectural Sansevieria (Mother-in-Law’s Tongue) creates a stunning, modern contrast.

Material Thickness: The Potanical Advantage

Here is a pro-tip that many people miss when consulting a standard pot sizing guide: External vs. Internal Diameter.

A concrete or clay pot often has walls that are 3-4cm thick. This means a pot that looks huge on the outside might be tiny on the inside.

This is why we love the fiber-cement and fiberglass technology we use at Potanical. Our pots are engineered to be incredibly strong but with thinner walls. This maximizes the internal volume, giving your plant’s roots more room to breathe and making the pots significantly lighter to move.

It’s the perfect marriage of heavy-duty style and lightweight functionality.

Still Unsure? Let Us Help.

Getting the size right can be tricky, especially if you are buying online. But you don’t have to guess.

At Potanical, we are more than just a store; we are your design partners. If this pot sizing guide didn’t solve your specific query, send us a message or visit us at our Modderfontein store with your measurements.

Better yet, if you are looking to overhaul your entire space, our Home & Office Consultations take the guesswork out completely. We will measure, source, and style everything for you.

Ready to find the perfect fit?