Hey Dennis,
The point of boiling is to denature the enzymes that cause the holly to go grey (technically called "browning" in the food science field). Unfortunately, boiling also tends to cook the wood much like kiln drying does. A little oxalic acid will shorten the required boiling time. I don't know how long it takes, but I would guess that it's much less than you think.
Let us know what you find out, will you?
By the way, a nice wide, pure white piece of holly can be made into a translucent, thin turning that resembles fine porcelain. Just saying'
Cheers,
Tom
ps. Not to belabor the point but: The staining is not just because of a fungal infection. It is because of a peroxidase enzyme in the wood (think of an apple browning when you cut it). That is why it happens so fast after cutting. Once you have the color, it is very difficult, if not impossible to reverse.
If you have the opportunity to harvest more holly, you can borrow my steam box, which will get the wood to temperature much faster than boiling, and without as much damage.
_________________
"There is no path to peace, peace is the path."
Mohandas K. Ghandi