Jeff (and Roger...and I suppose everyone else, too), YES, it is my understanding that you CAN create the flame in box elder quite easily. Earlier this year, I spoke with Dr. Sarah (the spalting pro out west). She quite flippantly mentioned that you can do it by simply drilling some holes in the tree. The flaming will start just like that...
BTW, I know I've mentioned this before, but just to add some info here: Again, from my understanding, any pigment in wood caused BY THE TREE is NOT colorfast. That is why the flames in box elder fade, cherry gets darker, walnut lightens, and ambrosia maple changes (more on that in a minute). The reason that these pigments change is that the tree does not expect UV light to ever reach it. So, the pigment is not protected from it. ON THE OTHER HAND, pigments caused by fungi ARE colorfast. Fungi (spalting) live in the sunlight. They are prepared for it. So, black line spalting will stay just as crisp, greys, blues, pinks, and greens will stay just as vibrant as when you first see them.
On ambrosia maple: There are two things going on here... The ambrosia beetle bores into the tree. This introduces fungi (call it mold if you want, but Sarah takes issue with that
) INTO the tree. As the fungi grows and spreads in the tree (the first discoloration in the wood), the tree reacts by "surrounding" the fungi to protect itself (the second color). If you've ever taken a good look at ambrosia maple from a very healthy tree, you'll see that there are two distinct colors/bands in each streak. So, ambrosia in maple is both a spalt (fungi) AND a tree reaction. The former is colorfast, the latter is not.