Vibrantly colored tulips pop up everywhere in the Netherlands when warm weather heats the low-land country’s fertile sandy soil each spring.   The best place to appreciate the beauty and variety of this prized flower is Keukenhof Holland, an English landscape-style garden in Lisse, about 30 miles south of Amsterdam. The perennial with cup-shaped petals is cultivated by the acre at Keukenhof, but the show only lasts eight weeks each spring.   To learn more about my visit to the world’s most beautiful spring garden,...