Sunflower

The Sunflower the second plant you get in the game and it's one of the three sun-producing plants that the player acquires. It's an essential plant, as sun is the resource of the game. The Sunflower can be upgraded to the Twin Sunflower if bought from Crazy Dave's shop, which produces double the sun.

In the music video at the end of the game, Zombies on your Lawn, a Sunflower is the lead singer. (Voice & Music by Laura Shigihara).

The Sunflower is based on the Helianthus annuus [1].

Suburban Almanac Entry
Sunflower

Sunflowers are essential for you to produce extra sun. Try planting as many as you can!

Sun production: normal

Sunflower can't resist bouncing to the beat. Which beat is that? Why, the life-giving jazzy rhythm of the Earth itself, thumping at a frequency only Sunflower can hear.

Cost: 50

Rec harge:  fast

Usage
The Sunflower is the primary sun-producer throughout the entire game, although replaced with the Sun-shroom for nighttime levels, and often upgraded to the Twin Sunflower in later levels. If planted, the Sunflower will produce 25 sun right away after 5 seconds, then the usual 24 seconds for the rest of the game. This also applies to nighttime levels. Just before releasing the sun, the Sunflower will light up in a yellowish white hue, as if the Sun is in her body.

Strategy
Since sun is the form of energy required to grow your defense, producing more sun means you’ll be able to grow a much larger force. With that in mind, you’ll typically want to have at least two full columns of Sunflowers (10 or 12 of them, depending on which areas you are playing in), although some players prefer one column. The Tree of Wisdom recommends planting two columns of flowers, although this is not really necessary; eventually enough sun builds up that, due to the extra plants, there are no more places to plant anything.

As Sunflowers do not ever do any damage, they must be protected at all costs. Putting them in the back row (the leftmost, closest to your house) is good practice. However, some people put them in front of their ranged offensive plants (like Peashooters) as a last line of defense before their offensive plants (which they put in the back) get eaten, giving them more time to kill the zombies.

If there are Catapult Zombies in the level, you should plant Umbrella Leaf nearby to protect them from basketballs. If there are Digger Zombies, and the Sunflowers are in the back, you should plant Pumpkins around them to protect them to prevent them from being eaten or if you haven't acquired the pumpkins, they should be placed second fom the back to avoid being eaten and instead put any instant on the back (or a split pea).

Trivia

 * The Sunflower is the only plant to ever verbally speak (during the credits while ending, There's a Zombie on your Lawn) when it sings the leading role. It is voiced by Laura Shigihara.
 * This might be the reason why sunflowers are given mouths.
 * This also means it's the only plant to have a known voice, as most plants say something in its almanac entry but we never hear them say it.
 * The Sunflower is available as a prop called "Flower Seed Packet" in the Xbox Live Marketplace for 5000 Microsoft Points. A watering can and soil will appear, followed by your avatar dropping three seeds into the soil and then watering them. A Sunflower will then pop up and sway a little, causing you to sway as well. The Sunflower will produce some Sun that you catch and hold for a bit. Everything then disappears.
 * Also, Sunflower glasses are available in the Xbox Live Marketplace for 80000 Microsoft Points. Other than the name, they have nothing to do with the Sunflower as they are just glasses with a pink/girl blue/boy colored frame and clear glass. In the future, there will be a Sunflower toy in the Game of The Year Limited Edition.
 * The Sunflower's Suburban Almanac entry states that the flower bounces to the beat of the earth. However, the bouncing may be an indication of when it will produce sun because the flower produces sun approximately twenty bounces.
 * The Sunflower is the main representative of the plants.
 * As the flower is being eaten, it will flash back and forth between its appearance right before it releases sun and its normal state.
 * This is because a plant or zombie flashes when it is damaged.
 * In I, Zombie, when you steal a sunflower using a Bungee Zombie, 250 sun will instantly come out at once from the sunflower.
 * The Sunflower, Sun-shroom, Gold Magnet, Magnet-shroom, Marigold and the Twin Sunflower are the only plants that can glow.
 * The Sun-producing plants and the Marigold glow when spitting out an object (i.e. Sun and Money respectively) whereas the Magnet-shroom and the Gold Magnet glow when attracting an object, caused by their electrical charge.
 * In the Plants vs Zombies website, when on the Zombatar tab, a Sunflower with yellow hair can be seen in a corner of the screen.
 * The Sunflower is one of the plants that appear on the loading screen, the others are: Peashooter, Repeater, Wall-nut, Tall-nut, Cactus and Chomper.
 * The Sunflower will glow if it's about to give sun to the player.
 * The Sunflower is a female. This makes her the only female besides the Cactus, the Marigold the Twin Sunflower, the Hypno-shroom and the Umbrella Leaf.
 * In the MMORPG World of Warcraft, exists a Quest, which, after you've beaten a PvZ-like minigame, rewards you with a pet, wich looks exactly like the Sunflower and sings sometimes.