"We were delighted to supply several hundred Arundo donax," said owner Neil Lucas of Knoll Gardens, which provided the zoo with the reeds.
"The bamboo-like reeds originated from the same part of the world as these giant vegetarians."
The four endangered adult and two young Asian one-horned rhinos, both born at ZSL Whipsnade, were now enjoying life in their refurbished home, he said.
The zoo recently spent £1m on new surroundings for the rhinos including indoor heated pools to allow the extended family to wallow all year round.
"Visitors to the Rhinos of Nepal are catered for in the zoo's first fully green exhibit, with features including a specially designed watchtower and spacious viewing area."
ZSL Whipsnade Zoo horticultural team leader David Hicks said: "The staff at Knoll Gardens were helpful and the plants provide great value."