If I recall correctly, the beams are wrapped in white oak. Oak can have fairly loose and swirly grain patterns which makes it more difficult to get a seamless look. In our case it was very difficult to find wide planks from the same milling (tree).
At install you will want to glue the backside and use clamps to hold it together -- it is best to splice the pieces with a biscuit joiner. Here is a photo during the install :

Thanks! I love the picture. We ended up wrapping ours in cedar. Mostly because we liked the look and it was cost effective. We ended up doing some hand painting of stain to hide areas where dark grain hit light grain...and it actually worked pretty well. The beams are pretty high up.I love this house. It looks like you did an amazing job.

Thanks very much -- the architect is excellent. I love the house too and it was one of my favorite builds -- the kind I would like to live in myself!
Cedar is a great option for beams too - the grains are pretty --- and of course it smells wonderful. I used cedar more than any other material when I used to build homes in British Columbia.
All the best!