We have four young seedlings of globe artichoke Violet de Provence that we sowed a few weeks ago. They are in the usual sort of 3.5 inch plant pots that, for most crops, would serve well for several more weeks. Artichokes, though, are deep rooted. Importantly, they develop a deep taproot, and do so rather quickly. If left in these small pots for long, the taproot may become wound around the pot and they may not then establish well once planted out.
As I am not planning to plant the artichokes out for some weeks yet, we potted them on; a slightly odd thing to do when their second pair of leaves has only just appeared and the root ball is so underdeveloped otherwise. Knocking them out of their pots, the taproot was clearly visible, so it may well have been detrimental to leave it any longer. Though they look quite silly now, they have been moved on to large pots of about one foot deep, which should give them plenty of space to develop without causing problems later on. The potting mix included a good scoop of manure and a sprinkling of fish, blood, and bone, which should sustain them well until they are planted out.