Alan Horsfield 
The Green Ambulance Caper [EPUB ebook] 

Have you ever described someone as a couch potato or called a dud car a lemon? How do you think this makes a potato or lemon feel? Tiffany finds out it’s not fair to the plants.
But there are people who are really nasty to plants — the Topiary Twins, Nettle and Thistle. They do dastardly things. They even keep some plants captive. They are villains of the worst kind.
Tiffany discovers Bindi and Dusty Thorn have a green ambulance. They care for plants that have been mistreated and try to stop the vile schemes of the Topiary Twins.
To be really successful there must be a showdown with the twins… Not something to be relished!