The evils of wide board construction are a frequent topic on every woodworking forum I read. A novice woodworker asks the question: "what is the widest board I should use?" and the answer is almost always: "if the board is wider than 6" rip it, alternate the growth rings and glue it back." In my opinion, this does not look nearly as professional or traditional as single board construction. Historically, wide boards have been used in blanket chests, panels, and table tops that have remained stable and flat for centuries. Successful use of wide boards requires good wood, proper handling, and good woodworking technique.
Throughout our house we have very wide boards. In the great room the random width floor has numerous runs with widths in excess of 10 inches with the widest being 17 inches. The 15+ inch pine and poplar panels are one board wide. Dan's horizontally pine paneled office has several wide board runs of 14 inches. He wanted the widest boards we had at the time. None of these have warped in spite of a humidification system that is not functional. The boards shrink and swell like crazy but they stay flat. Even some of the left over 10+" wide boards left on the floor of the planing room for four years have not cupped. The pine is Southern yellow by the way. It came from good trees, large straight and tall. Much of the wood for floors is quarter/rift sawn but of course the wide boards I have been referring to were plain sawn. They have sapwood and heartwood together in the same board. The ash board which makes one counter top is 22" wide, cut just off the center of the pith and completely flat.
I have been told by old cabinetmakers that the best furniture was made from air dried lumber that had seen at least seven years of changing seasons. Though we seldom use seven year old wood, we try to apply that practice of allowing as many natural and or artificial "seasonal" cycles of shrinking and swelling to our lumber. It is important to start with as good a quality of log as you can. I have found that small trees (less than eight inches in diameter) and those which have grown very quickly will be more prone to instability. Species is also a consideration. Some species are normally more stable than others. The way the wood is dried affects stability. We try to allow our lumber air drying time before being put into the solar kiln. When in the kiln, the wood experiences moisture loss during the day. At night the humidity comes back up allowing the wood to "relax" a little. This first alternation of moisture loss and equalization helps relieve drying stresses that might accumulate otherwise. The wood is dried to about 8-10% and then solid packed in one of the barns where it will stay until needed when I am ready to use the wood, it is put into our dehumidification kiln to be brought back to 6-8% before milling.
I realize that everyone does not have access to lumber that has been handled as ours. However, I can make some recommendations for those who have the space and time to stockpile a supply of wood in which they have confidence. First, try to find a small mill that specializes in good wood. They will usually be the ones cutting for quality not quantity. These mills often know the history of much of the wood, how long it has been air drying, where it came from, etc. Most likely the owner will not be trying to earn a living (a little humor here). Sometimes the owner will also be a woodworker. Look for auctions and sales that include lumber. We, for instance, had the opportunity to buy a barn full of walnut that was then over sixteen years old. If you have the room, buy green lumber and take good care of it. Get a moisture meter.
What if you don't have any room for wood storage? Get a moisture meter. Check that "kiln dried" wood. Kiln dried only means that at some time in the history of the board it came out of a kiln. I always think about seeing a pile of tongue and groove flooring or maybe paneling sitting out in the yard at a local lumber dealer. It happened to be raining at the time. I could only shake my head and wonder about the poor homeowner who was going to get that stack. As with everything else be a wise educated consumer.
Another recommendation is to learn about your medium. It seems to me that many woodworkers have little knowledge about how wood behaves. Wood moves. Joinery is the science of putting two or more pieces of wood together so that they don't destroy each other when they do move. There are many good books available. You can't learn too much about reaction wood, case hardened wood, honeycombed wood, moisture content, shrinking swelling, etc., etc. The Internet is a great place to learn many things but there is no substitute for good books. Actually it is sort of scary to think that there are novice woodworkers who are trying to learn basics via Internet. Last, remember that the wider the board, the more it will move. Flat sawn wood will move more across the width of the board than quarter/rift sawn wood will. Wide board construction requires the use of proper joinery techniques to compensate for that movement