Podzol

Podzol is a grass-type variant block that will be featured in the Mega Taiga in 1.7. Similarly to grass blocks, it can only be obtained by using the command, the creative inventory, or by digging it with a Silk Touch-enchanted tool; otherwise, it drops dirt instead.

Podzol will allow mushrooms to be placed on it no matter the light level, and allows the growing of giant mushrooms, which suggests it's similar in coding to Mycelium. However, unlike Mycelium it can have saplings, and other plants placed on it. On the other hand, it does not spread like Grass and Mycelium do.

Trivia

 * When Podzol has Grass, Dirt or Other Podzol blocks placed on top of it, its texture changes to the dirt texture, but it will never actually change to dirt, no matter how long the block remains on top of it. (Mycelium does not have this effect.)
 * Podzol does not spread to adjacent dirt, unlike other similar blocks. This is because podzol is a type of soil, and has the same Block ID as dirt, just a different damage value.
 * Podzol appears to be comprised mainly of small grass scraps, dead leaves and moss.
 * Grass cannot grow on Podzol
 * In real life, Podzol is the type of soil usually found in coniferous forests in wet, cold areas as well as warmer areas.