Sir Boyd, 87, jumped on his own sit-on mower to tidy up a common area just yards from his iconic factory.
Thrilled locals watched as the multi-millionaire stepped up to maintain council ground in Uddingston, Lanarkshire.
He spent 30 minutes trimming grass as he sat on his four-wheel lawnmower wearing his trademark bunnet.
The area at Uddingston Cross sits next to sheltered housing and flats.
A clip of Sir Boyd’s green-fingered heroics has been circulating among townsfolk, who have congratulated him for his actions.
One said: “Sir Boyd is a well known figure in the village but this was another level.
“He is a man of action and just took it upon himself to get out and maintain public grounds without any complaints.
“People stood and watched open mouthed as he drove up and down cutting the grass.
“He’s a fine example to others and deserves recognition for his public spirit.
“He could have easily asked some of his employees to get the job done but he is the kind of man that just takes things on himself and there’s apparently no stopping him.
He is a man of action and just took it upon himself to get out and maintain public grounds without any complaints.
“He’s a familiar sight driving his big silver Rolls Royce around Uddingston but seeing him on his lawnmower was brilliant.
“Considering he is nearly 90, it’s quite remarkable.”
A source added: “Sir Boyd has lived in Uddingston all his life and could see that during lockdown some areas of grass had become overgrown.
“He was happy to give it a trim and tidy it up.”
In March this year, Tunnock’s announced they were temporarily halting production of their world famous teacakes and caramel wafers amid the coronavirus outbreak.
They said it was the only way to prioritise the health and well-being of their 600 staff and stop the spread of the virus.
Bosses were praised for paying employees 90 per cent of their wages during the closure.
The firm also donated thousands of treats to frontline medical and construction staff working at NHS Louisa Jordan in Glasgow and said it was their way of “applauding” key workers.
Sir Boyd, who created the Tunnock’s teacake in 1956, revealed The Queen told him she preferred the teacakes over caramel wafers when he received his knighthood at Buckingham Palace.
Alistair McKinnon, head of facilities at the Waste and Grounds Services department at South Lanarkshire Council, said: “The land in question is maintained by the council.”
“In fact, it was cut recently as part of our programme of grounds maintenance which is back underway after the Scottish Government updated its guidance, allowing this work to start again. The council is working hard to clear a backlog of work after several months of lockdown.”
Tunnock’s declined to comment.