Japanese larch (Larix kaempferi) is a resinous, moderately durable conifer widely planted in the UK and northern Europe. Compared with European larch it often reads a little darker and redder, with a strong, abrupt earlywood/latewood contrast and frequent knots that give boards a bold, rustic character.
It’s a solid exterior softwood when detailed properly: good stiffness, decent above-ground durability, and strong fixing performance. The practical workshop realities are resin and knots—both can be hard on cutters—and a tendency to split near edges if you nail or screw without pre-drilling.
Japanese larch is commonly used for cladding, fencing, outdoor structures and boat planking where you want a tough, locally grown softwood that can handle weathering better than spruce. In many yards it’s sold simply as “larch,” because its working and performance envelope overlaps heavily with European and hybrid material.