These are some of the stools I've grown. As can be seen, although they have all been grown on the same jig, each stool (or table!) has its own character, depending on the species of tree used, the finish you apply, and the size, shape and material you choose for the top.
An elegant stool in sycamore. The decision on whether or not to strip the bark should dictate when you harvest the stool. If you decide to leave the bark on for a 'rustic' look, harvest when the sap is 'down' and the tree dormant in the winter. If you harvest during the summer growing season the bark can be stripped off quite easily.
The grafts on this Maple stool frame took exceptionally well. When this happens the growth of the frame takes place almost exclusively in the 'legs', which become much thicker than the 'rails'. These become redundant to the growth process, remaining thin.
Of course grown stools will never look machine made, but they can be finished with varying degrees of rusticity. If you prefer the natural look, simply harvest your stool in winter and finish it with the bark on. I like the two tone appearance of this stool, achieved by stripping only certain parts of the ash frame.
This table was left to grow for seven years, and is consequently a lot sturdier than the rest. It's one of the advantages of growing your own stool - if you want it stronger, leave it in the ground longer. The structure doesn't get further from the ground, it just gets thicker.
The growing stool doesn't need much attention - I usually check them about every three weeks - but if left for too long during the growing season stems may grow misshapen and become difficult or impossible to correct. When this happens, an interesting version of the intended shape can sometimes result!