Wood, being a hygroscopic material that absorbs and releases humidity, undergoes variations in volume and shape. Seasoning is a process aimed at reducing humidity in the wood, thus limiting dimensional variations.
In parts such as the center of the cart wheel (hub) it was crucial that the wood did not expand or contract because this would have given instability to the wheel and the cart itself, given that the wheel constitutes its load-bearing element. The wood used by the cartwright therefore had to be seasoned for a very long time (at least one or two decades).