I'm thinkin' something's wrong . . . 6" in 6 weeks. That's NOT normal! Next time it needs water, stick a shovel in the ground several inches away from the stalk (where you don't think there are any related roots, but as close as possible without hitting the roots) and pull back a little, SLIGHTLY lifting the plant. Continue doing this all the way around the plant, then water. If it's gonna grow, this should get it going. I'd do this on a cooler, cloudy day, or in the evening. Hitting/cutting a root or two shouldn't cause any permanent damage.
Your plant should be much taller than you say it is, genetics be damned!