Czech larch contains a large proportion of resin, which can leak out when the sun heats it up. Due to the high content of oily substances in the wood, larch will last a very long time in outdoor areas even without surface treatment. Over time, sun, wind and rain will stain the reddish-brown larch wood, giving it a typical silver-grey patina. Czech larch has more knots in larger sizes than Siberian larch.