I have a number of mop-head hydrangea plants that I have grown on in various size pots that are surplus to my requirements. They are available for sale in 3 litre pots at £3.90 each and in 7.5 litre pots at £7.50 each, collection only. Those in 7.5 litre pots are really large plants. Flower colour ranges from pinks and reds to whites. Hydrangea colour, unless white, is affected by the alkalinity or acidity of soil, acid soil produces blue colours and alkaline red.