A head gardener says it is like having a baby snatched from him overnight - after years of hard work were laid to waste in hours due to the tidal surge.
The Secret Gardens in Sandwich were submerged in more than 5ft of water last Friday, as storms battered the county.
Now the owner of the Grade II listed area, at The Salutation, has said the cost of the damage could run into millions.
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People wade up to their waists in water at the secret gardens
The hall lies just metres from the River Stour and The Quay - which was one of the worst hit areas in the region.
In 2007 the gardens were fully restored and opened up to the public after lying neglected for 25 years,
They are home to thousands of plants and even a rare plant dating back to the Jurassic period, which is part of a global conservation project to boost its numbers.
So far it's thought up to £300,000 worth of damage has been caused by the flooding.
Water and debris cause huge damage during the tidal surge
Inside the house there was also extensive damage. Still from the video.
Owner Dominic Parker, who appears in hit Channel 4 show Gogglebox, said: "Right now we have a small team from a fire and flood damage company who are working hard to repair the damage to the cottages on site and are due to start working on the nightmare down at the bottom of the garden today.
"Visually it looks like a bomb went off, there's an awful lot of damage where the water came up over the bank and under the fences.
"It pushed a hell of a lot of soil over the pathways, which we're busy trying to clear.
Tens of thousands of pounds of damage to machinery and thousands of hours of hard work is ruined.
Dominic Parker, owner of the Secret Gardens at the Salutation in Sandwich
"Inside the workshops everything has collapsed, all the walls have swollen and are contaminated.
"We have someone coming out today to see if any of the machinery can be salvaged."
He said a lot of the rare species of plants, which were sitting in a metre and a half of salty water, are only now being looked at, and some may not survive.
He added: "About 25% of our gardens were under salt water, containing the bulk of herbaceous plants we have planted out there.
The Salutation Gardens. Picture: Peter Winkworth
"If it all goes then the sky's the limit as to the cost of the damage.
"It may be another couple of weeks or months before we know the full extent of the damage, which could run into the millions."
Mr Parker said the site's huge compost reserves - or black gold - have been contaminated.
"It's very distressing for the whole team and particularly so for the head gardener. It's like seeing his baby snatched from him overnight" - owner Dominic Parker
He said: "It's very distressing for the whole team and particularly so for the head gardener. It's like seeing his baby snatched from him over night."
Mandy Richardson-Mills from the British Monarchist Society set up the campaign after visiting the site since she was a girl.
She said: "It was heartbreaking to see all of their work washed away. We're the garden of England at the end of the day.
"We're contacting nurseries, garden centres even celebrity gardeners in the county appealing for help.
Video: The devastation caused by the tidal surge
"Anything they can do, even donating plants, would help.
"It was hard for us to watch last week, for them it must have been horrendous."
She said there was also a knock-on effect of damage to the restaurants and tea rooms.