Moulding planes that would have this in particular are those with quirks of some sort that need a sharp area of a profile to project from the sole. Side bead planes are a good example of this. However, the sharp edge of a plane that receives high wear such as a rabbit or filister plane would commonly be boxed since its edge would be presented to the work repeatedly. At other times you may see the inside corner of a complex profile moulding plane's integrated fence being boxed since the fence would be pressed against the stock to keep the profile in position during the cut.
|Cove with fence boxing and side bead with boxed quirk|
|Rabbit plane with persimmon boxed edge|
So where can you get boxing wood? It is a real challenge. So I am going to help you identify some wood that is native to the US that you may be able to find that is appropriate for boxing. I am also going to share a source of Buxus Sempervirens that is sold here in the US currently.
First off is a native source that is the only North American tree in the Ebony family. It may be a surprise but it is Persimmon (Diospyros Virginiana). This wood is possibly in your backyard or neighboring forest and you didn't even know it. It often goes unnoticed because the forest grown trees may not bear fruit since they don't receive enough sunlight if they are in the understory growth with taller trees around. These trees often don't grow in groups and are sparsely populated in the forest. This could be due to an animal such as a deer eating the fruit and then the seed germinates wherever the droppings land. Generally I find the trees growing along the tree line to an open area or a path through the woods rather than out in the middle of the forest.
Here are some pictures of the most important way to identify the tree, the bark. You need to know what the bark looks like because very likely the tree that is big enough for you to cut down for lumber will be too tall to see the leaves well. The forest grown trees will be slim and tall with the foliage grouped near the top. Also the best time to cut most trees is during the winter months while the foliage is lost.
|~9"ø Persimmon bark|
This is the bark of a relatively small tree, about 9" in diameter. Just large enough to get usable wood. Notice the bark is a rusty red color where it is broken. This is a good way to confirm you have the right tree.
|~14"ø Persimmon bark|
Now notice the bark if this much older Persimmon. It is much different. It looks more like a mosaic of plates of bark rather than ridges. This tree is about 14" in diameter by comparison.
This is a piece of persimmon lumber cut so that you can see the layers of bark. Notice that the layers alternate black to rusty red. The bark will break at the reddish layer. The layer that divides the bark and the inner wood is quite distinct as well.
|Plain sawn Persimmon|
This is the color of the wood that has been milled and air dried. It has taken on a light flesh tone color that will darken to a beautiful light brown tone when oiled.
Last, the supplier of Boxwood (Buxus Sempervirens) is Rare Woods USA. The owner is Rory though anyone one can help you that answers the phone. He is from South Africa and began importing exotic lumber to the US about five years ago. He is not new to the business since he worked with exotic lumber in South Africa for about 25+ years. I learned of his exceptional stock of woods from Tim Manney. Thanks Tim! He spoke well of Rory and after speaking to him myself I got the same vibe. He really knows his wood and very quickly understood what I was inquiring about. He does have a minimum order so please be aware of that. Currently it is $300+ shipping. This accounts for his valuable time in selecting the right boards that you may want. He also has quarter sawn European steamed beech for plane making up to 8/4. I encourage you to check out his video about his lumber on his home page. You will see what a unique place he has. If you buy from him please let me and others know your experience by posting in the comments below. I have not purchased anything from him but wanted to pass on the source.
Here are a few photos of some boxwood that I have. It was a very old tree by North American standards. It does grow here in the US but it is hard to come by in this size. You will mostly see it as very small hedges around homes, etc. I really love the smell of this wood.