The macro is:
/cast Milling
/use Peacebloom
/use Goldthorn
Keep adding frequently used herbs till the 255 char limit. Or make multiple macros, I guess. Does break if you have odd stacks though (non multiples of 5).
For completeness:
/cast Prospecting
/use Saronite Ore
(Not tested, there may be a typo, I just recited them from memory)