Book about Vines that turned into horse

[Karla Montes]

Several years ago I read this book about a group of children that were working at this like factory or work camp, can’t remember which exactly, in this area by a big forest and they decide to escape one day and magically enough the bushes and vines turn into horses which they ride. This isn’t a children’s book and I’ve been racking my brain trying to figure it out.

[Tab]

How many years ago did you read this?
Was this for teens or adults?
Did the majority of the book focus on the kids working at the camp, or the time after they escape?
Part of a series?
Time period story takes place?
Anything about the cover?