Sunny Days/Strategies

First Level (Level 1-1)
This achievement can be done easily by accumulating sun in the first level. First, plant a Peashooter, and the wait for Sun to start falling. Collect them all until you have 8000 sun before planting the second Peashooter, and the achievement is unlocked. This works because the first Zombie will not come until the second Peashooter is planted. The time needed to get this achievement is very long, though. This does not work on the first level if you have already beaten the game once because level one will appear differently.

Second Level (Level 1-2)
Plant the first 2 Sunflowers. Collect sun until you have 8000 sun. The first zombie won't come before the 3rd Sunflower is planted.

Normal Strategy
The strategy is described like this: Play a Day/Pool level that has 3 flags (level 1-7, 3-2, etc.). Keep building Sunflowers in rows 1, 3 and 5 and put 2 Garlics at the front of each row. Then in the other rows, put a few offensive plants such as the Peashooter, Snow Pea, Repeater (Gatling Pea should not be used because of its high cost), Cabbage-pult, Kernel-pult and Melon-pult etc. If replaying level 1-1, only one Repeater or two Peashooters are necessary. In about column 7 (6 if in the water), plant a Wall-nut/Tall-nut with Pumpkins protecting them. Finally, fill out the remaining spaces behind the defensive plant with Sunflowers. You can use Sun-shrooms and/or Twin Sunflowers.

Alternatively, you can also plant Spikeweed and Spikerock instead of offensive plants (if playing level 1-1 or another simple level). This is especially effective if planted in front of defensive plants.

Last Wave Strategy
During the final wave, kill all zombies except about 1-3 zombies. Dig up all plants (except for Sunflowers) and plant Sunflowers in their place. Block the zombie(s) with a Wall-nut/Tall-nut, then collect Sun until you get more than 8000 sun, then kill the zombies with an instant kill (make sure that after you use the instant kill you have 8000 sun or more).

Breaking the Limit Strategy
Submitted by Red suplexknight

Plants
Begin by placing a Sunflower or Imitater Sunflower on any column. Once a zombie shows up, place a Squash and kill it. Then, place Garlic on the last rows (except for the top,middle and bottom). Then, place a Split Pea behind the Garlic. Place three Garlics on the top,middle and bottom rows of the 3rd to last column. After that, Place some Spikeweed on the fourth to eighth row. Place Sunflowers where the zombies can't go,and if possible, upgrade to a Twin Sunflower. Keep going (and occasionally replace Garlics) until you get the achievement. You may also reach the maximum amount of Sun!
 * Sunflower
 * Imitater Sunflower
 * Squash
 * Spikeweed
 * Split Pea
 * Pumpkin (optional)
 * Garlic
 * Twin Sunflower
 * Spikerock (optional)

Filling the Pool Strategy
If you have unlocked it, play the Zombie Nimble Zombie Quick Mini-game. Start by planting Sunflower on the first column of all the grass rows. For the first Zombie you will have to use a Squash on it, then when the second one comes, plant a Lily Pad. Then place a Cattail on it. Do this for both water rows. Cattails will attack all Zombies in all rows, even backwards. They are as fast as Repeaters also, and having them in a fast paced level makes them better. Now continue planting Sunflowers on the second column. Slowly upgrade them all to Twin Sunflowers. Also plant Wall-nuts on the 3rd or 4th last water rows to slow down Dolphin Rider Zombies. Plant 6 (3 per row) Cattails in total. If you do it correctly, you should get it during or slightly after the third wave.

Survival: Endless
Build a strategy that lasts long enough to collect Sun. This is very easy if you have good timing on Digger Zombies and Imps.

Survival: Day and Survival: Day (Hard)
Plant a column of Repeaters at the back, plant a Tall-nut in column 7, plant Spikeweeds in front of the Tall-nut. Fill out the remaining spaces with Sunflowers, and upgrade them as fast as you can, as well as upgrade the Repeaters and the Spikeweeds.

You could also use that same strategy, except replace Repeaters with Chompers and Tall-nuts with Pumpkins. Place Chompers in the 3rd and 4th row, or beyond. Place Pumpkins on top of the Chompers. Put some Spikeweeds and/or Spikerocks in front of the Chompers, and fill the rest of the empty spaces with Sunflowers.

Survival: Roof (Hard) and Survival: Roof
Just plant Twin Sunflowers at the end of each row and play as normal. Just try to be lucky to not find any Bungee Zombies orCatapult Zombies. Seriously, it can be problematic if you find one.

Seeing Stars
Fill the specified spaces with Starfruits but leaving one. Then keep collecting Sun until you have enough, and simply plant the final Starfruit.

Plant Peashooters and Sunflowers (one in the back of each row). Start getting Starfruit and fill all the spaces but one. Upgrade Sunflowers into Twin Sunflowers now. Replace Peashooters with Melon-pults. Try to fit two Melon-pults in each row and place Tall-nuts in front of them. Use Squash, Jalapeno and Cherry Bombs when mobs of Zombies arrive. Keep on doing this until you get 8000 sun.

Zombie Nimble Zombie Quick
Simply applies the method "Last Wave Strategy" above, although in this level, you can even max out at 9990 a lot faster. This is also a good candidate as it is a long level, being 4 flags, and the fast pace of the level makes the job of collecting that high amounts of sun much less boring and cumbersome as levels with normal speed.

Zombiquarium
Simply continue in the Mini-game without buying the Trophy. This is probably one of the easiest and fastest ways to get this achievement. Make sure you have lots of Snorkel Zombies.

Note: This will not work for the iOS versions.

To do this with Grounded and Flower Power
Take Sunflower, Twin Sunflower, Garlic, Fume-shroom (with Coffee Bean), Flower Pot, Tall-nut and Potato Mine (Squash works too), with the rest slot fillers, to any regular Roof (preferably without Gargantuars or Catapult Zombies) level. Plant 3 Sunflowers in rows 1 and 5, with 4 in row 3. When the first Zombie comes, Potato Mine/Squash him. After that, plant 3 Garlics in column 1 of the same rows as your Sunflowers. Then, begin planting Fume-shrooms in rows 2 and 4, creating a maximum of 4 per row. Wake them up when Zombies get in the same lane as said Fume-shrooms. Now, begin planting Twin Sunflowers where the Sunflowers are. If you begin your Twin Sunflowers before the first huge wave of Zombies, you could have all 10 by the final wave. When the Final Wave comes, take out all but a few Zombies in one row, and dig up every Fume-shroom in that lane. Delay said Zombies with a Tall-nut. If done correctly, you could take out three hard Achievements in one fell swoop.

Note: Some versions cannot get the Achievement via Zombiquarium.

Survival: Day
Earns Sunny Days and Flower Power

1st round
Plant Sunflowers in lanes 1,3,5 two garlics in front of each. Use Potato Mine for the zombies when earning sun for Gloom-shrooms. Upgrade some of the sunflowers to Twin Sunflowers. This round should end with 500 to 1000 sun, sometimes 2000 sun.

S - Sunflower

Ts - Twin Sunflower

Fs - Fume-shroom

Gs - Gloom-shroom

G - Garlic

2nd round
This round must end with 2000 to 3000 sun, sometimes 4000 sun.

S - Sunflower

Ts - Twin Sunflower

R - Repeater

Sn - Snow Pea

K - Kernel-pult

Tn - Tall-nut

Sw - Spikeweed

Gs - Gloom-shroom

G - Garlic

3rd round
This round must end with 5000+ sun.

M - Melon-pult

Sr - Spikerock

4th-5th round
By the 4th or 5th round, there must be 8000 to 9990 sun to earn the Sunny Days achievement.

Plants
Start planting 3 sunflowers. When a zombie comes, use Potato Mine. When you have 8 sunflowers, save sun for a Cattail for the next zombie. Before the first flag, there must be a Snow Pea in every lane, 2 cattails on the pool, and 2 Tall-nuts on the pool. Every flag, add two Cattails and two Twin Sunflowers. There must be a Tall-nut in every lane before the second flag.
 * Sunflower
 * Twin Sunflower
 * Snow Pea
 * Cattail
 * Tall-nut
 * Potato Mine
 * Tangle Kelp
 * Lily Pad

S - Sunflower

Ts - Twin Sunflower

Ct - Cattail

Tn - Tall-nut