All our outdoor pots can be planted directly into and have been sealed at the factory to reduce moisture loss through the porous structure of the pot.
You can seal the inside of the pot but it is not strictly necessary. If you want to maintain as close to an "as new" finish for as long as possible, you could consider applying an additional sealer. This will reduce the moisture coming through to the outside of the pot which may over time affect the appearance.
On light coloured pots this reduces the chance of leaching that may occur from some potting mixes.
In some cases this matters, in other cases it doesn't. If it would matter to you then seal the inside of the pot with an all purpose pot sealer. Something like Yates Pot-a-Seal is fine, it can be brushed on or comes in an aerosol and is available from most hardware stores.
If you have any questions about this, we're happy to help. Please Contact Us.