The idea behind this strategy is to abuse Thyme Warp to infinitely stall the horde, then defeat them with instants. The naturally dropped sun is enough to pay for the plants, although you can use Sun Bean in conjunction with Cherry Bomb or Power Lily to earn more.
No standing plants are used; this strategy is meant to deal with hordes of Hair Metal Gargantuar in endless levels.
Remember to only use Thyme Warp when they are right next to the lawn mowers. Use Stallia to further slow the horde.