Credit: The Spruce / Jenny HughesLast year, garden and cooking maven Martha Stewart made a visit to the Longwood Gardens in Pennsylvania. Nothing about this surprised me—Longwood Gardens is one of the top botanic gardens in the United States. US News and Reports named it number one only a few weeks ago.In her blog post, Stewart encouraged her readers to visit, and I couldn’t agree more. Last spring I made a trip to Philadelphia and set aside a f…