While reading this article about an Oregonian nominated to be the White House gardener, I learned this bit of historical trivia:
President Woodrow Wilson brought in sheep to graze on the White House lawn during World War I as part of the war effort. They kept the grass trimmed and their wool was auctioned to raise money for the Red Cross.
For more fascinating facts about the history of the White House garden, see this NYTimes article and watch this cute video.
By the way, growing and canning your own food is an excellent way to be prepared for disasters!