The Far Future introduces 'power tiles' these are tiles that are effectively joined and when you place a leaf on one of the plants sitting on a power tile, all the plants that are the the same type of power tile will get the boost effect!
Watch out for the jetback zombies - you may need the tall-nut!
Here is a list of the plants that you will unlock in this world.
Laser Bean - Level 2
Cool plant which fires a medium strength laser down it's lane hitting all zombies in it's path.
Blover - Level 4
If you need a little more time, this handy plant will blow away all zombies in the air. I don't use this one much to be honest.
Citron - Level 7
I do like this plant - It's really strong, a bit like the laser bean but more heavy duty. This fruity plant does not mess around. Will stop most zombies in it's path with one shot, but the recharge time can be a little high, so make sure it is well protected.
E.M. Peach - Level 10
This plant explodes and disables all machines in an area. Very useful especially in this world where a lot of the zombies are well equipped.
Infi-nut - Level 14
This nut will regain lost strength over time, but it's overall strength is less than a standard wall-nut.
Magnifying Grass - Level 18
This plant can be strong it you are happy to spend sun on making it stronger. Tap it to utilise some of your sun for an attack.
Tile Turnip - Level 25
You can use this plant to turn an ordinary tile into a power tile.