Agriculture in Space

Government Executive reports that the first vegetables grown in space are now being harvested and eaten.  (Some lettuce grown under LED's.)

In the past I've criticized some vertical farming schemes which claimed to rely on sunlight to grow their vegetables.  In the case of the space station, it would seem they'd have 12 hours of sunlight and 12 of darkness, so they shouldn't need LED's.  On the other hand, the sunlight lasts only 90 minutes or so at a time, so maybe they can't rely on the sun.