Marigold

The Marigold is the only money producing plant, and only appears in Plants vs. Zombies. It is like the Sunflower except it makes money instead of sun. It is also the first plant the player receives for their Zen Garden (they start out with two marigolds in their Zen Garden). It resembles a small flower. In the Zen Garden, it can be many colors. It is also the least expensive plant in the Zen Garden.

Suburban Almanac Entry
Marigold

Marigolds give you silver and gold coins.

Special: gives coins

Marigold spends a lot of time deciding whether to spit out a silver coin or a gold one. She thinks about it, weighs the angles. She does solid research and keeps up with current publications. That's how winners stay ahead.

Cost: 50

Recharge: slow

Usage
Planting the Marigold costs 50 sun. Every 24 seconds or so it produces either a silver ($10) or a gold ($50) coin, with gold coins being rarer than Silver Coins.
 * Note: These are best used in conjunction with Gold Magnets, as the player will probably be too busy tending to their other plants to collect the money themselves.

Strategies
The only purpose of Marigold is to give the player money. Outside of this, Marigolds are near-pointless due to the slow recharge and no attacking powers. However, Marigolds are great space fillers in early levels (when playing Adventure Mode again) due to the lack of stronger zombies and potential for hoarding excess sun. In later levels, Marigolds take up too many valuable slots to be worthwhile (especially on the roof). Another strategy is to plant an entire row of Marigolds with a Gold Magnet and one or two Garlic or Imitater Garlic plants in the front to divert the zombies away, although Gargantuars, Catapult Zombies, and Zombonis can get annoying sometimes.

Marigolds are commonly used in the mini-game Last Stand for gold farming.

Giant Marigold
Giant Marigolds are bigger version of Marigold seen in the Cancelled Mini-game, Big Time. It gives out more coins than the normal Marigold.

Zen Garden
The Marigold is a plant obtainable for the Zen Garden. Upon finishing Level 5-4, the player can obtain the Watering Can from the final wave of zombies, which will subsequently grant access to the Zen Garden. Crazy Dave will then appear to introduce his or her Zen Garden. Unlike the Marigold in the main game, the Marigold in the Zen Garden comes with a wide variety of petal colors: As with all Zen Garden plants, Marigolds can drop gold and silver coins periodically for the player if they are happy. More Marigolds may be bought at Crazy Dave's Twiddydinkies for $2500, which restocks with three Marigolds every day; there is no limit to purchases in the Nintendo DS version, and for some versions changing the system time will restock the shop. To prevent easy gold farming, Marigolds sell for $3000, which is $5000 less than regular plants' selling price, and give fewer coins and diamonds on reaching each stage of growth. Unlike other plants in the Zen Garden, Marigolds start out as a small flower, while all other plants begin as identical sprouts. A fully grown Marigold can be sold to Crazy Dave for a net profit of $1500.
 * Royal Blue
 * Royal Red
 * Purple
 * Lavender (or Hawaiian Flower)
 * Cyan
 * Blaze Orange
 * Magenta (or Fuchsia)
 * Canary Yellow
 * Pink
 * Light Green
 * White (this is the standard color for Marigolds in the main game and the only color in the iOS and Android Zen Gardens)

General

 * Marigold, Sunflower, Cactus, Flaming Pea, Ice Queen Pea, and Power Flower are the only plants referred as female.
 * If the player looks closely, they will see a single tooth on the Marigold's mouth. It shares this trait with the Cattail, the Starfruit, and the Potato Mine (Plants vs. Zombies 2: It's About Time only)

Plants vs. Zombies

 * Marigolds are the only plants that can be bought for the Zen Garden, with the exception being the plants that the player can buy from Crazy Dave in the iOS and Android versions for various prices.
 * Though Marigolds planted in the game modes all have white petals, Zen Garden Marigolds come with many different petal colors (Gray, Red, Pink, Orange, Yellow, Green, Blue, Cyan, Purple and Magenta). When a Zen Garden Marigold is highlighted by the watering can in the Nintendo DS version of Plants vs. Zombies, it may change color instead of lighting up. The color it changes to depends on the color of the Marigold, and the petals may not change entirely, leaving small patches of the original color.
 * Rather than starting as a sprout, Marigolds in the Zen Garden start as little flowers with three petals.
 * The player will get a Marigold in their Zen Garden before they get it in Adventure Mode.
 * In Versus Mode, the use of Marigolds is prohibited to prevent Versus Mode from being used as a tool for Gold Farming.
 * During a level's final wave, both Marigolds and killed zombies stop producing coins. Even newly-planted Marigolds will only produce three coins or so before stopping. Interestingly, in Seeing Stars, Art Challenge Wall-nut, and Art Challenge Sunflower, when the player reaches a certain point, the same thing happens, and the player stops getting coins. This glitch does not appear in the Android version.
 * Marigold sprouts can be seen growing in the loading bar on the title page before a Zombie head shoots out of the lawn.
 * The fact that it produces coins is a pun on its name, which has the word gold in it (Marigold).
 * The Marigold actually resembles a common daisy more than a marigold.
 * This is one of the few plants that do not have any offensive or defensive abilities.
 * The Marigold is one of the plants that glow. The others are Sun-shroom, the Magnet-shroom, the Gold Magnet, the Sunflower, and the Twin Sunflower.
 * The Marigold is one of the three flowers in the game, the others being Sunflower and Twin Sunflower.
 * Since Marigolds are more commonly used in Last Stand for Gold Farming, it is often forgotten that they have a slow recharge rate. This may be due to the fact that the player does not need to wait for it to recharge between waves.
 * The player can tell the direction a Marigold flower is going to face during the first stage (which is right after purchasing it). The sprout will face either left or right; if it faces right, the Marigold will face left when it becomes a flower, and vice versa.
 * The Marigold is one of seven plants that is not available in Versus Mode. The others are Lily Pad, Tangle Kelp, Sea-shroom, Blover, Flower Pot, and Plantern.
 * This plant is the only roof obtained plant that doesn't have a fast recharge.
 * If the bend in the stem faces left, the Marigold will face left (as shown with the white Marigold).
 * If the bend faces right, the Marigold will face to the right (as shown with the red Marigold).
 * Some people try to change dates on their computers to let them buy more Marigolds for more money (the player would already need a lot of money to buy food for his or her plants).
 * The sprouts in the loading screen are Marigold sprouts.
 * Mari.jpg is a bug in the Nintendo DS version of Plants vs. Zombies where Marigolds' stems and petal colors get messed up when the player is about to water them or is about to give them chocolate. This bug is only present in the Zen Garden.