Smooth, porous blond wood, lighter than cork, grown mainly in Central and South America; the most popular core material for surfboards in the 1940s and 1950s.

Surfers initially used balsa in combination with redwood; Pacific Systems Homes, a Los Angeles-based house-building company that dabbled in surfboard construction, built redwood-balsa composite boards as early as the 1930s. All-balsa board became standard in Southern California after World War II, when boardmakers Bob Simmons, Matt Kiv...