I forgot to mention the .rpa files maintain the original folder structure internally, you need to match that too. The garden stuff goes in \game\scripts\Garden, just create the folders manually and it should work.
And yep, the garden.rpy you uploaded is very different from mine (image below, yours on right), I'm assuming I have the "correct" version since I get no errors but they're so different it's hard to tell. Mine doesn't even have 564 lines.

Pretty sure I downloaded the full version again when v0.19.1 came out, and since you downloaded the update files that's probably where the issue comes from.
Edit: well, turns out the garden.rpy in the current release is the same from v0.18.2, and the update-only package doesn't come with a garden.rpa so it can't be the culprit. Which means the one you currently have could be a leftover from a test version that didn't make it into the public release? Wherever it came from, I suggest you do a full download when you can, who knows what other differences might be there.