Yay I was able to get fresh hay souvenirs I upgraded my petting zoo in chapter 6 before the actual goal 3 to upgrade the zoo, now I have 2 white planks in the workshops and I'm able to collect hay till they are done woohoo!!!!
How to hoard hay
For this ,you have to max on planks before the 'make 5 planks' in chapter 4
Then upgrade the zoo, and now you'll be able to make 6 more , goal 3 of ch 4 autocompletes
In chapter 6 ,after giving 15 rope , make 4 planks ( totally 10 in inventory) and upgrade the petting zoo. since goal 2 is to make 5 planks ,the option to craft it will still be available
Then make 2 more planks AND the ability to hoard as much hay as you want is available till you reach goal 3 !