Paulownia (Paulownia tomentosa) is the second lightest wood in the world. The tree is native to Japan and Korea.
Perhaps the wood’s greatest attribute is that it’s both lightweight and strong. The Average Dried Weight is 18 pounds per cubic foot (or 280 kg/m3) according to the Wood Database.
Paulownia is also one of the most stable woods with regard to humidity — it has very low movement in service.
It grows like a weed, and Paulownia trees are frequently plantation grown.
The low density of Paulownia provides excellent buoyancy — making it highly suitable for boat building — especially for surfboards and kayaks.
The most common test for measuring wood hardness is known as the Janka hardness test. The test involves measuring the amount of force required to embed a .444″ (11.28 mm) diameter steel ball into the wood to a depth of half the ball’s diameter.
See the Wood Database for more information on Paulownia and other woods.