This is a particular crop that grows in a 3x3 plot of tillable soil when the player plants 9x of the same crops, and they all grow to be gold quality or higher. This will then cause this plot to grow into a giant crop, which offers more crops than you planted, which are all guaranteed to be gold standard or higher. This is a nice boost, but truthfully, most players will tend to keep the giant crops on their farm as a permanent fixture as they will never wilt or die, even as the seasons change, making them a fantastic decoration for your farm.