Pot size C2, C3 and C5: what do nursery pot sizes mean?

A C2 nursery pot holds roughly 2 litres, a C3 roughly 3 litres and a C5 roughly 5 litres. The C stands for container and the number for the volume in litres. The diameter in centimetres varies by grower, so always measure the rim before you choose a decorative pot.

You may have seen it: you buy a plant at a garden centre and the label says C3 or C5, while the pots you are comparing are listed in centimetres. That takes a little puzzling. Here we explain what those pot sizes mean, how to turn them into a usable diameter and which planter or cachepot fits.

What do pot sizes C2, C3 and C5 mean?

Growers use container sizes. The number after the C tells you roughly how many litres of potting soil fit in the pot. A C2 holds about 2 litres, a C10 about 10 litres. It is a volume, not a length, which is exactly why it is hard to compare with the centimetres you see on a decorative pot.

As a rule of thumb, since every grower uses slightly different pots:

• C2: about 2 litres, roughly 15 to 17 centimetres across.
• C3: about 3 litres, roughly 18 to 19 centimetres across.
• C5: about 5 litres, roughly 21 to 23 centimetres across.
• C10: about 10 litres, roughly 27 to 30 centimetres across.

Treat these numbers as a guide. A nursery pot is usually tapered with a rim wider than the belly, so two pots with the same C size can differ by a few centimetres.

How do you convert a C size to centimetres?

The easiest way is not to calculate but to measure. Measure the opening of the nursery pot on the inside of the top rim, edge to edge. That is how you measure any pot. In our guide on choosing the right flower pot size you can read how to take that diameter and why you add 2 to 4 centimetres.

If there is no size on the pot, let the plant guide you. Look at the height and the width of the root ball. The ball should fit comfortably in the new pot, with a watering rim of a few centimetres left at the top.

Which decorative pot fits a C2 or C3 nursery pot?

A nursery pot does not have to come out. Many people place the plant in its original pot inside a nicer cachepot. Then allow 1 to 2 centimetres of room all around, so you can lift the inner pot out easily when watering. How that works is covered in our article on using a cachepot with an inner pot.

For example, a C3 with a 19 centimetre rim fits a decorative pot with an inner diameter of 21 to 22 centimetres. A C5 of 23 centimetres needs a cachepot of about 25 to 26 centimetres. Go for an extra centimetre rather than one too few, because an inner pot that jams is a nuisance in the long run.

When do you move from C2 to C3 or C5?

Fast growing plants are best repotted into the next size: from C2 to C3, or from C3 to C5. Jumping two sizes is usually too much. In an oversized pot the soil stays wet for a long time, the roots get too little oxygen and root rot is waiting around the corner.

When repotting, choose peat free potting soil, as Milieu Centraal advises, and water generously afterwards so the soil settles around the roots. Make sure there is drainage too. If you wonder whether a pot needs a hole, read flower pots with or without a drainage hole.

Does a handmade mosaic pot suit a nursery pot?

Certainly, but remember that handmade really means handmade. Every piece from Masr Potten & Vazen is made by hand and no two are identical. The rim may be a fraction oval, which is a trait of handwork, not a flaw. So always measure the shortest side and use that as the size for your plant.

The collection starts from around €135 and ranges from compact bowls to amphorae of about 120 centimetres. See what is available in our collection of handmade pots and vases. Do you have a particular size in mind, for a row of plants or for a business premises? Custom work is possible in colour, model and size, and you are welcome to request a no obligation quote: you receive a proposal within two working days.

If the pot is going outside, choose a frost resistant pot with a drainage hole. Not all terracotta is frost resistant, and moisture freezing in the wall can make the pot crack.