kinda copy paste my answer of a similar question/problem:
Just go to the official wiki and look up the item details:
http://lifeisfeudal.gamepedia.com/Flax_stemhttp://lifeisfeudal.gamepedia.com/Shovellenghts means how big the item is and can only be placed in containers which can hold 4 or higher in lenght.
i just see that the lenght storage stuff is not on the wiki, maybe i will add it later there but that you get an idea how this works:
traders cart can store up to 7 (so even ore, soil etc can be stored)
chest can store items with a lenght of up to 4 (shovel, flax stems, boards etc)
barrel and crate can store only stuff which is 3 or lower afaik and so on
so yea, it is kinda messy right now to store stuff like boards, flax stems without the loot bags