Herb bonus for trees.

Exactly what is the distance for any herb patches to be effect in blocks?

I'm not entirely sure that it's distance based within your homestead. I had assumed that it just meant "near" as in "within the confines of the homestead" instead of near to each other with a fading effect if you put it across the homestead. To be fair, it should have the same effect as the other boosting items, so lemme double check the success rate of my refining when I put my furnace across my homestead from its booster, as opposed to right next to each other.

All right, I just checked, and it looks like I was grossly mistaken. Based on my check, it looks like anything that has a boosting effect must be within one tile (either diagonally or horizontally) of the item it is affecting. That means that if there is a tile of space between the two, they won't be boosted. So, here's a diagram, if I can get it working:

+-+-+-+-+-+-+-+-+-+-+-+
| | | | | | | | | | | |
+-+-+-+-+-+-+-+-+-+-+-+
| |i|i|i|O|O|O|i|i|i| |
+-+-+-+-+-+-+-+-+-+-+-+
| |i|i|i|O|O|O|i|i|i| |
+-+-+-+-+-+-+-+-+-+-+-+
| |i|i|i|O|O|O|i|i|i| |
+-+-+-+-+-+-+-+-+-+-+-+
| |O|O|O|X|X|X|O|O|O| |
+-+-+-+-+-+-+-+-+-+-+-+
| |O|O|O|X|X|X|O|O|O| |
+-+-+-+-+-+-+-+-+-+-+-+
| |O|O|O|X|X|X|O|O|O| |
+-+-+-+-+-+-+-+-+-+-+-+
| |i|i|i|O|O|O|i|i|i| |
+-+-+-+-+-+-+-+-+-+-+-+
| |i|i|i|O|O|O|i|i|i| |
+-+-+-+-+-+-+-+-+-+-+-+
| |i|i|i|O|O|O|i|i|i| |
+-+-+-+-+-+-+-+-+-+-+-+
| | | | | | | | | | | |
+-+-+-+-+-+-+-+-+-+-+-+

In this, the X would be the location of the boosting item, and the i and O would be the location of anything to be boosted. (i and O were both used to help make it at least a little more readable) The blank spots are areas where nothing would be boosted. Keep in mind, this is assuming that both the boosting item and the boosted item are 3x3, which I'm unsure is true for everything. What I'm trying to say is that the items have to be directly touching, I suppose.

Then you can just move the boosting item/herb patch to get a boost? o.o

No. It has to be right next to the item at the start of the day (or, when you put seeds in the farm for the well, or plant the herb patch, etc). Otherwise, no boost. For example, I planted my first bloody herb patch before the apple tree, and, despite the apple tree I planted right next to it, I only got five herbs, when the minimum with a boost is 6. At the same time, something like a furnace will get the boost automatically as long as the tree that boosts it is right next to the furnace. In other words, your herbs have to be touching the boosting trees at midnight, but you can move the furnace around so that you can be more or less likely to fail on refining to train it. (Because the furnace itself is not consumable, while herbs are)