Speaking at the newly re-opened Garforth garden centre in Leeds, Hewitt, who is to become Klondyke joint chairman, said Klondyke will continue its redevelopment strategy for several years across almost all of its 22-centre estate.
Edinburgh will redevelop from June 2017 for opening in early 2018.
Falkirk will quadruple in size with a new restaurant and relocated head office in the building, to open in phases from 2018.
Garforth has a 224-seater restaurant in a model that other centres are being given too.
Klondyke now has seven restaurants similar to the Garforth design.
Yardley said: "We want to concentrate on ordering at the counter and the food being brought to the table and away from a hot food counter, because food dries out."
Hewitt, who previously had 16 years at Wyevale Garden Centres, said catering is 22 per cent of sales now and could be 25 per cent in three years time when redevelopments at Edinburgh, Polmont (Falkirk) and Weavervale (Northwich) are done.
He added: "Until 5-6 years ago the company acquired centres and didn't spend money on them but I said to [owner] Dorothy Gault if we get planning to redevelop we'll get good money out of them. Redevelopments are the best way to make money on capital."
The Garforth covered planteria is 4,000 sqft, outdoor is 8,000 sqft and the shop is 26,000 sqft. The former Savilles nursery, bought in 2001, closed in 2014 for a complete rebuild. Turnover could reach £3.5m-£4m annually, having previously been £1m a year.
Yardley added on planterias: "Having a big planteria is not the right thing. You can get two or three deliveries a week so don't need one."
Hewitt said: "A lot of our planterias are too big. A lot garden centres are finding that. [Flagship] Carlisle is too big, so we'll cut it and add a shed concession. It makes it more manageable for staff. We will not just maintain space for the hell of it."
He said of his 26 years in garden retail, which he came to from Sainsburys, that there was increasing competition for garden centres, including from retailers such as Dunelm and The Range.
Hewitt, who said he had "throughly enjoyed" his career, added: "People found easier to make money in the early days. They were all basically horticulture businesses with very small gift offerings and non-existent Christmas apart from trees. Over the years ranges have expanded in giftware and farm shops and cookware have come on the scene. Back then, restaurants were small and most were coffee bar type franchises. Now most people run their own and it is a huge growth area."
He said the biggest thing he pushed strategically six years ago was to invest in catering.
"People need to continue to invest. The customer expects better standards and nicer facilities."
Yardley said staff training would be a big focus in the next five to ten years.
Klondyke has doubled turnover in the last decade to £48m and could reach £52m at the end of the next financial year.
Daniel Lawton, formerly of Beverley Garden Centre, is Garforth manager. There are 75 full and part-time staff.
See more in next edition of Horticulture Week.