According to a nearby information board:

The raised beds you see in front of you are a recreation of an 18th century garden. Research has shown that the soldiers at Fort Montgomery had gardens to supplement their food supply. Although we do not know precisely what the soldiers were growing we can speculate on the types of crops they might have had, that were popular in the region during the period. Taking this into account, in this garden we have grown turnips, carrots, peas, lettuce, onions, squash and beans. Many of these crops were relatively easy to grow and preserved well during the cold winter months when vegetables were direly needed. To learn more about how vegetables were preserved before refrigeration, visit the root cellar exhibit in the history museum at Trailside Museum and Zoo (a short hike away!)