Some offer plants in P9 pots which are plants often less than 1 year old, many varieties of which can be more difficult to establish straight out in the garden. Most pot sizes are referred to by their volume capacity in litres, with the exception of pots that are smaller than 1 litre which is usually referred to by the diameter or cross section of the top of the pot (P9 is approximately a 9 x 9 cm pot).

10 Inch Plant Pots - Etsy UK

So, always look out for the pot size the plant has been grown in – its critical best value for your garden and budget. All afternoon I've been looking for somewhere that tells me what size, as in diameter, a 10 litre pot is. Clearly, a plant in a 2 litre pot has twice the root system of one that initially may look slightly cheaper in a 1 litre pot but often offers worse value for money. The table below gives the approximate measurements of the common pot sizes we use at Jacksons Nurseries.

Some suppliers avoid ensuring pot size is clear at the point of purchase so their plants look inexpensive but in the long run, they can result in slower development and increased losses.