Pumpkin patch

What is the meaning of the "patch"?
It's from the song "This is Halloween" of Marilyn Manson

Patch means a field or a garden.

'Patch' is in the WR Dictionary:

a small area of land for growing something : a cabbage patch.

In this case it's a pumpkin patch, obviously.

Click here to view images of pumpkin patches.

But are they sincere?

Just a note to say that OP might be confused because Marilyn Manson is covering a song that originally appeared in the Tim Burton animated movie "The Nightmare Before Christmas". There are no actual lyrics in the song about pumpkin patches, but in the movie a few lines of the song are sung by ghostly cartoon pumpkins floating above the patch where they once grew. If bogdan looked up the lyrics to the song online, he may be mistaking these attributions as part of the lyrics:

SHADOW:
"Boys and girls of every age, wouldn't you like to see something strange?"
SIAMESE SHADOW:
"Come with us and you will see - this, our town of Halloween"
PUMPKIN PATCH CHORUS:
"This is Halloween, this is Halloween, pumpkins scream in the dead of night..."