According to a 2009 post over at PlantingSeedsBlog.com, the five first ladies most committed to gardening at The White House include:
5. Patricia Nixon, wife of Richard Nixon, who organized the first garden tours at the president’s residence
4. Edith Wilson, wife of Woodrow Wilson, who kept sheep on the grounds
3. Michelle Obama, wife of Barack Obama, who re-installed and expanded the home’s WWII-era vegetable garden
2. Eleanor Roosevelt, wife of Franklin Roosevelt, who insisted upon the creation of a victory garden during WWII
1. Abigail Adams, wife of John Adams, who planted the first fruits and vegetables at The White House
This seems about right to me.