Mr and Mrs Mahindar Singh, both 70, from Fishwick View, Fishwick, said their garden has been raided every week since the beginning of spring.
The couple said they feel "under siege" from green-fingered thieves who are snatching plants, hose pipes, solar lights, hanging baskets and garden ornaments under the cover of darkness.
Mr Singh said the thefts have become so common that he and his wife "dread coming home" for fear of discovering more of their plants and property missing.
"We just don't know what we're going to find when we come home", said Mr Singh.
"They've been taking things from our garden for years, but this year it's happening every week.
"It's very upsetting. We have nurtured some of these plants, especially our Yucca plants, for years.
"For someone to just come and help themselves to our garden, taking whatever they want, it's just not right."
Mr Singh said he took up gardening following his retirement from Royal Mail in 2014, where he worked in the sorting office for 33 years.
He and his wife became keen gardeners and their back yard, with views of the former Fishwick Golf Course, soon flourished with lush plants and vibrant colour.
"I've worked all my life, since I was a young boy of 15", added Mr Singh.
"This garden is our pride and joy, and we work so hard to keep it nice, you know?
"It's something that me and my wife enjoy working on together. But all our hard work, it feels as if it's all for nothing now.
"We only have the one hanging basket left now, all the others have been taken. It's just getting too expensive to replace them."
But Mr Singh suspects that the thieves' motives might be more sinister.
"I think they are jealous and I think it has got to the point where they are trying to intimidate us.
"We have tried to secure things down with wire, but they have cut the wire and left it on our doorstep for us to find in the morning."
In another recent raid, the brazen thieves uncoiled and stole a set of string solar lights that had been fixed to the outside of the home.
Mr Singh said he had been handed some Neighbourhood Watch-style stickers from police, which he fixed to his front door as a deterrent.
The stickers, warning would-be thieves that the home is monitored by police, were peeled from the door overnight.
Mr Singh found the stickers the next morning, plastered on a nearby wall where another hanging basket had been stolen.
"I think they are trying to scare us. It's not just petty theft. They are trying to make a point, that they can take whatever they want, whenever they want", he said.
"This is our home. This is where we are supposed to enjoy our retirement and feel safe.
"But my wife is afraid of waking up at night and finding them in our garden. It's just gone too far now."
Mr Singh said he decided to speak out to raise awareness among his neighbours and the wider community.
He added: "It can't only be us that they are stealing from. There must be others, other retired people maybe, who are being targeted and who are too afraid to speak out."
Lancashire Police have been approached for comment.