Cheapest priced copy (The List): $3.49 at Card Kingdom, near mint, their price list as of .
Elephant Grass 
Enchantment · Uncommon · Visions · #104
Cumulative upkeep {1} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
Black creatures can't attack you.
Nonblack creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
2 printings · $3.49 to $3.99 at Card Kingdom
One ruling from Wizards of the Coast
- 1 February 2014Unless some effect explicitly says otherwise, a creature that can’t attack you can still attack a planeswalker you control.