1.   Because leeks grow partially underground, they are dirty, with grit wedged between their layers.

2.   But then truffles grow underground, on gnarled old tree roots.

3.   The brown squiggly parts at one end are where the roots used to be when it grew underground.

4.   The yuca is a tuber that grows underground, like potatoes, and has a bland, slightly sweet potato like flavor.

5.   A peanut display, for example, will show how the flower grows above ground while the pod grows underground.

6.   Since potatoes and sweet potatoes grow underground, they are less vulnerable to sudden weather fluctuations.