Lewington said "poor trading conditions and lack of business" meant he had closed after taking over in 2011.
The Cumbrian centre has a new cafe and house on site but Lewington said he had been working 80-hour weeks to keep afloat.
He added: "Supermarkets, hardware shops and other shops supply lots of garden products nowadays which have also made it a lot harder for us."
He said he had had one good season out of the last five. Lewington said he had not decided what to do with the site. He has previously had plans to develop leisure and camping on the site.