Posted: 06/03/2015 at 12:48
Watery, a 9 cm pot should be sufficient for tubers from Wilkos. If not a 12 cm. pot up in dry compost for now and lightly water in a week,or so. Pot on frequently as roots fill their pots ...and they will grow fast now. One tuber per pot.
i grow dahlias by reporting often and have several in large ....5 litre or larger.....pots. They will grow and flower well if well fed during the summer, esp if john Innes used. I also grow them on in pots ...for reason you give...until I know exactly where I want them in the garden.