Flower Power

Plant 10 Twin Sunflowers in a level, and beat it without them dying. Hard?

Strategy
You cannot play Survival: Endless to get this badge, Last Stand, or conveyor-belt levels, as it needs to be a finished level. And in Last Stand you cannot bring Sunflowers, or Twin Sunflowers. And conveyor belts don't bring sun-producing plants or upgrades.

Get 10 sunflowers, and steadily upgrade them to twin sunflowers. At the end of levels, before you get money or plants, plants still recharge, so if you have enough money, staying about 5 minutes gives you time to plant all 10 upgrades.

Trivia

 * This achievement is possible in the Night, as you can stack up on sun and use it on Twin Sunflowers.