Lanarkshire-based BHC is building the sister centre to Berwick Garden Centre which is owned by Nick Crabbie.
East Lothian had originally rejected the development two years ago but the scheme was given the go ahead on appeal by Scottish ministers last April.
Meanwhile Alfords Garden Centre in Laceby, Lincolnshire has gone on the market with Scotts Property after owners Peter and Dee Skiba decided to retire.
Scotts are marketing the 0.7ha centre as a "thriving" business or a "retail and residential development opportunity".
Planning permission has already been granted to extend the coffee shop by 100 sqm and to either extend the five-bedroom bungalow on the site or knock it down.