Whole Foods Market (WFM) reported earnings after the bell today, and slowing sales sent WFM stock plummeting on heavy volume after hours.

Whole Foods earnings beat expectations by a penny for Q4 and the full year. But WFM stock investors got skittish when the company missed an already-low revenue bar for both periods.

WFM posted sales of $3 billion in its Whole Foods earnings report vs. expectations of $3.04 billion. That represents just 2% year-over-year growth.

Wall Street’s expectations for 4% growth were anemic enough, though the grocer did have accounting quirks to blame. In fiscal 2012, Whole Foods earnings enjoyed a 53-week calendar year that’s back to normal for the current fiscal year.

The Whole Foods earnings report also revealed $12.9 billion on the top line for the full fiscal year vs. Wall Street’s hopes of $12.98 billion. That’s growth of just 10% — the company’s lowest annual rate since 2009 and a far cry from the nearly 16% growth WFM posted last year.

Slowing same-store sales played a role in the WFM revenue miss. Annual comps growth for WFM was north of 8% for the past two years, but was expected to drop to 7.2% or so. Instead, same-store sales growth slid just below 7%.

Apparently, just after hearing those numbers, WFM stock investors got wise to the high premium on their shares. WFM stock had built up a trailing P/E north of 40 thanks to a 40% run from Jan. 1 to just before Whole Foods earnings were released.

Thanks to the ugly Whole Foods earnings report, WFM stock is now testing its 50-day moving average around $59. While that level could support the stock, a break lower could mean even worse fortunes for shares.

As of this writing, Alyssa Oursler did not hold a position in any of the aforementioned securities.