President Jude Livingston explained the size of the donation was unexpected following the circumstances in which the event was held.
Even after refunding tickets for out-of-towners unable to attend due to Covid-19 restrictions, a total of $45,000 was made from attendees visiting the 42 gardens on display in November.
The majority of last-minute sales came from people based in Rotorua, but the lead-up to the event was daunting, Livingston said.
"We did a lot of cutting of costs."
The two charities were well ahead of others nominated when it came to gardener's votes, she said, and so it was decided $10,000 would be given to each.
"I was afraid we wouldn't be able to give anything, maybe $1000."
Livingston was therefore extremely surprised when the treasurer gave the green light for the money to be donated.
The Rotorua Daily Post Christmas Appeal for the Rotorua Salvation Army Foodbank concludes on Saturday after six weeks.
Rotorua Salvation Army Corps officer Kylie Overbye explained she had been surprised by the $10,000 donation.
"It was definitely a welcome surprise."
The money would go towards food provisions.
She also expressed gratitude for everyone who had donated so far and acknowledged it had been a challenging year for some.
Overbye said anyone still wanting to donate could do so.
The annual appeal, run by The Rotorua Daily Post, with the Rotorua Weekender and The Hits Rotorua 97.5FM, aims to raise food and money for the local Salvation Army foodbank to help it continue its work throughout the Christmas period and into next year.