1. The main location in a popular video game called Fallout 3 ( Basically a destroyed Washington D . C )
2. The real Washington D . C could still be considered a Capital Wasteland due to crime , crooked cops , crooked politicians , as well as it's strange on again off again gun ban laws that violate the constitution from the same country and so forth.
( example 1 ) Gamer 1 : " I killed a super mutant at the capital wasteland. "
When you try talking to a friend who seemingly ignores you for days at a time and gives no attention back, and overall acts like they don't want to be your friend anymore. Just like giving water to a dead plant, the plant will never grow again or give anything back. Hence the name, watering a dead plant.