Plants have been swiped from the Sunken Gardens in Westbrook.
Hellebore, Erysimum Bowles Mauve, tulips and rosemary, which were all in flower, have disappeared over the last week.
Sunken Garden Society volunteer group founder Peter Hasted said: “They have disappeared. All of the ones that have gone had been donated to the garden by the community or the Bumble Bee Conservation Trust.
“They are all in flower at the moment and were looking really good before they vanished, I’m guessing they looked too good and an opportunist pilfered them.
“There was a mention that it was a fox or wildlife, but they would have left the plants somewhere in the area.
“Luckily the society is not going to let this get us down and we will be replanting the garden.”
The SGS volunteers have been working to restore the gardens since 2017 after Pete, a coastal warden, set up the group.
Plans include restoring the path network to allow access for wheelchair users and extensive shrub restoration.
Last month tree planting took place at the site as part of the part of the Isle of Thanet Trees and Woods Initiative (ITTWI) which successfully secured £525,000 from the Urban Tree Challenge,
Sunken Garden volunteers and fellow ITTWI helpers planted six trees specially chosen to withstand the coastal winds.