A month ago, back on Mar 19, it had a similar spike in volume and price. Back then, they had just reported the launch of more than 100 new food, beverage, and personal care products. Longbow also raised them from neutral to buy, citing a recent survey of specialty retailers that found HAIN's biggest customer, Whole Foods Market had experienced strong traffic so far that month and boosted promotions, according to the WSJ. Another outfit calling themselves Trading Central also upgraded from Sell to Buy at that time.
Today, that same outfit Trading Central again upgraded from Sell to Buy again (they must be some kind of a joke outfit though), and Ned Davis Research also upgraded from Neutral to Buy (they have also been flip flopping too often to be taken seriously, like every week).
Aside from that, I think that, like you said it is beginning its earnings run and the shorts are deciding to get while the gettin is good. 15.7% short float and 10 days to cover at last settlement of 3/28. Nothing to sneeze at.