[Kajazy]

Anyone grown celery in pots? I have a spare compost-filled plastic tub (quite large - about 40 litres), and I have some celery plants - would this work? How closely can I plant them?

[Trillium]

It would work, but celery prefers a rich soil so if you have compost and manure, add and mix well.  Not sure how many plants you have, but you could space them about 6" apart in all directions. Celery is a bog plant so keep them watered well and regularly (if the container has drainage holes).