Staff numbers at Pennell's have risen to 80, an increase of 15.
Chairman Richard Pennell said: "We were keen to develop the centre further in order to strengthen the appeal of the business to customers in the Lincoln area.
"The support we have received from the Clydesdale Bank has been instrumental in helping realise this ambition."
He added: "Following recent development of the centre at Lincoln we have seen strong growth in sales of outdoor plants from our new canopy area and indoors from our new food hall. Our restaurant too has seen strong growth. Customers are looking for a wide range of experiences when they visit a modern garden centre."
New concessions are Leading Labels Clothing, Pavers Shoes, Field & Trek and Gary Simpson Butchers.
Clydesdale's Katy Simpson said: "It's great to work with and be able to support a thriving local business like Pennells Garden Centre.
"The company demonstrates the incredibly important role enterprising family-owned businesses play in the region and typifies their ambitious nature. We're particularly pleased to help the business expand its current offering to customers.
"Clydesdale Bank remains focussed on investing in the local economy and it's extremely rewarding to know that we can play a part in supporting the aspirations of ambitious firms like Pennells Garden Centres."