<p>I want to print a flowerpots, for advanced watering system.</p>

<p>Plants are going to be eaten.</p>

<p>What is the most suitable material, when we consider the fact, that we do not want to just make forms and do clay flowerpots(which may seem most healthier), but having them directly printed.</p>

<p>What are the temperatures that makes plastics emit dangerous components in surrounding water, and what are those components?</p>

<p>Is there some "totally safe" material out there? I was thinking of PLA or PETG, because I've already heard that ABS is not safe for edibles.</p>

If you break up a large piece into multiple smaller pieces and properly glue them together, you basically add stiffeners (as a result of printing walls). This could lead to a more stiff model; this might have been confused by calling large prints more brittle opposed to constructed models.
If printing is conducted at similar conditions on large printers, there shouldn't be a reason why the model becomes more brittle unless the conditions aren't the same. But that would be true for printing at small printers too, e.g. if one print was printed in a draft.