Efficiency of Single vs Double Sunflowers at the start of the level

Solution 1:

If there are no space constraints and you don't plan to use plant food on any of them, the single flower always wins out because 2 sun flowers cost 100 sun and produces suns at the same rate as a double sun flower.

However, this rarely happens as there's usually some kind of constraint on space as you go star hunting or do the challenge missions.

Typically, unless I absolutely need that extra plant slot for something critical to a level, I like to bring both sun flowers. I start out with a few of the normal ones (up to 3-4) and then switch to only planting double sun flowers.

The main benefit of the double sun flower is that a single plant food on it gives you twice as much sun, and I almost always use my first plant food for sun, which tends to make the rest of the level way easier.

Solution 2:

You should always start with a single sunflower because you can plant it immediately.

If you will wait for 2 suns to fall down to plant a double sunflower, you will lose precious time and sun that a single sunflower could produce.

I also noticed that rate of falling sun is a bit slower than sunflowers(correct me if I'm wrong). So if you plant a single sunflower, you will have 25 sun left. By the time that 2 additional suns fall from the sky, you will most probably produce extra 2 suns with a single sunflower. That will bring you to 125 sun total which you can spend on a double sunflower if you want.

But, as spartacus mentioned in his answer, I also use both sunflowers. With the only difference that I first plant 1 full column(5x) of single sunflowers, while killing first 2-3 zombies with potato mine and then I start planting double sunflowers.

TLDR:

Start with a single sunflower unless you are playing a level that only allows you to spend X sun. In this case you will most likely produce more sun that you are allowed to spent with single sunflowers(and their ROI is 25% better(producing a single sun for 50 sun instead of 2 for 125 in the same period of time))

Solution 3:

Space is at a premium, especially in Pirate and Ancient levels. The further left you plant your flowers the more time they have to work over the zombies. Planting one column of twin sunflowers will save space over two of regular sunflowers.

An additional consideration is the effect of plant food. Twin sunflowers give 250 sun, while regular sunflowers get 150. Thus the efficiency of your plant food is increased by Twin Sunflowers.

It's important to put together your sun production as quickly as possible. This means husbanding your sun so you can buy a Sunflower as soon as it's recharged. Twin Sunflowers make this more difficult, but with Sun Boost it only takes two sun to buy your first one. Using low cost delaying plants such as Potato mine and Iceberg Lettuce help.

A typical strategy of mine in an Endless Zone is to try to have plant food left over from the previous game. As soon as you have one twin sunflower planted, use food on it. Then you have 250 sun to quickly buy the next twin sunflower as well as to begin rapidly building defenses. Potato mine and Iceberg Lettuce can delay zombies to allow you to buy a high cost plant very early, such as Winter Melon.

I would recommend against using both twin and regular sunflowers. The slot is better spent on a plant to delay the zombies.