In order to grind out this stupid task, you’ll first have to get to a point early in the game. I highly recommend coming back to this achievement after you’ve completed everything else, especially the achievement for reading all the recipes. The reason for this is because you can only read the recipes right after completing the game and then choosing Continue from the main menu. Once you select New Game from the main menu, your chance to read the recipes is gone until you finish the entire game again.
If you play through normally, you’ll notice that after harvesting a few squashes and repairing the machine, some flies will infest your garden and you won’t be able to grow squashes for the rest of the game.
So here’s how to start the grind without (too much of) anything getting in the way:
Get to the point early in the game where you’re gardening and the machine breaks. You may have harvested a couple squashes at this point. Go to the back left of the yard and get some wood and use it to repair the machine. Edgar will say that it still needs oil. Go inside the house and get the cooking oil from the kitchen shelf and use it on the machine outside. Very Important: After using the oil, you’ll be able to harvest squashes again but DO NOT interact with the machine again. This causes the story to move on and flies will infest your garden, making it unusable for the rest of the game.
You can now start the miserable grind that absolutely ruins this lovely game. Starting on the left and going to the right makes harvesting easier. Just use the pickaxe on the plot, sow the seeds and water them to start the process on all 6 plots. A couple minutes later they’ll yield large squashes and you can collect them and start again on each plot.
This will take several hours as you can only do 6 at a time and need 500 squashes total. Also, you have to do them all on one save, in one sitting. I tried quitting to the main menu to see if my squashes would save and they didn’t. I had 41 in my inventory and reloaded to harvest 9 more but didn’t get the 50 squash achievement. So you apparently can’t quit to the main menu until you’re completely done. I personally won’t be getting this achievement as I don’t have 5+ hours to grind it out without quitting.
If someone has a better method or suggestion, please let me know. I’m pretty pissed about this horribly designed achievement that serves absolutely no purpose.