Atomicrops

Year Recommended: 1
(Year one typically is the most forgiving with health, seeds, and money.)

Method

• The best method for this achievement is to get as many soil expanding scrolls and seeds as you can. Only try and plant what you have 5 of or more and keep 4 of each seed on your character.
• You will need 80 spaces of tilled soil to plant the 20 large crops and those spaces need to be placed so that you are able to make a large crop. (If you need, take a picture of the screen and pause the game to count spaces.)
• I believe I waited to/was able to plant all 20 in the fall. I would not recommend planting the large crops as you get them, since the slugs tend to eat them and the witches can throw their bombs at them.
• Once you have 4 of all 20 seeds that you are going to plant, start planting them at the beginning of the day, on a day without a boss. Planting them at the beginning of the day gives you the best chance to get all 20 planted without any crop eating/destroying enemies showing up.

Crop Info

Here's a list of the crops, seed icons, and where to find the seeds for each crop. List of Crops and Seeds. I believe that there are 19 different crops (including the sunflower) and that a large heart or large rose will have to be planted as well as those 19 others. I could be wrong and let me know in the comments if I am, but I don't think mega/large trees count.

Edit: I just wanted to include that I got this achievement on June 23rd 2021, around the Doom and Bloom Update.

At the current update, this achievement can't be done normally anymore as the plated crops will keep evolving. Instead you'll have to find all 20 crop statues instead and the achievement will pop + reward from the fly-mutant guy.