Podzol

Podzol is a grass-type variant block that will be featured in the Redwood Forest in 1.7. Similarly to grass blocks, it can only be obtained by using the /give command 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, which suggests it's similar in coding to Mycelium

Trivia

 * 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.