"Rent, rates, food and wage costs are getting higher, so you have to make cost efficiencies," he said. "Putting up prices should be your last resort."
This needn't mean "penny-pinching" though, he added. "If you're offering an affordable luxury like Dover sole, don't discount it. Put it on social media and charge £20. It's about margins, not percentages. Steak also will never go out of fashion."
With the National Living Wage already having an impact, "the worrying trend is that employers will take on under-25s, who won't give the level of service and hospitality that your customers expect", Harris pointed out. "Meanwhile, some caterers are buying their staples from Tesco rather than from wholesalers."
Harris described running a restaurant as "a beast", adding: "You have to be on the numbers 100 per cent - don't wait till halfway through the next month to see how you're doing. Cost your menu items to see which make margins and which cost you. And watch your waste - I found £200 worth of food in one client's bins."
Among his suggestions for greater profitability were: "If you're in a city or large town, offer a delivery service, particularly if you can make a first-class burger. Promote your centre for business meetings, even business breakfasts. You have free parking and if 100 come probably 90 will never have been before. Events are easy to cater for as you know the numbers, you choose the menu, it's all done in one go and they pay up front."
Social media powers the rapid adoption of new food trends, though these may be little more than fads, he added. "Filipino cuisine is big this year but probably won't last that long. Tapas is still around - it's worth having a 'tapas corner'. Mezze needn't require much cooking and livens up a counter. Tartines (fancy open sandwiches) can also be very colourful."
High-end restaurants such as Ottolenghi use such colourful displays effectively, he explained. Meanwhile, "Old-fashioned comfort food like fish and chips and pies are coming back. But they don't need to look like those served in a canteen."
On drinks, "craft beers are really big", while Starbucks has introduced the fruit-based "Refresher" with green coffee extract, which "you can do in your own homely way".
He added: "Most of the worst food I've had has been in garden centres. But I've also had amazing tacos, oven-baked pizzas and home-made desserts. Nothing is that difficult with the right equipment and chefs with the right mindset." Local sourcing "is taken for granted and is something you should be doing anyway".
A range of caterers gave pointers to their success. Fron Goch Garden Centre catering director Melanie Sewell said the Gwynedd-based centre has gone from £1m to £3m turnover in nine years with £1m coming from the restaurant. Having spent £230,000 on a refurbishment last summer, including increased seating and extending the kitchen, it has already made back two-thirds of that, but the key to its success has been an emphasis on good service, she said.
"Consumer expectations have increased massively," added Sewell. "Even Nando's now have a meeter-and-greeter. You should smile and greet the customer before they do it to you. It's easier if you have colleagues who are naturally positive and make eye contact. Once you have a team like that it attracts others."
The centre has a three-month probation policy. "After that you have a good idea if they are right," she said. Staff should also talk in sentences rather than lists, even after a long busy day. "Giving good service is exhausting. Shorter shifts of four-to-six hours make it more achievable."
In exchange for this, she said: "I don't think the living wage is too much to ask," adding that staff account for 35 per cent of costs. "We used to aim for 33 per cent but found that's unachievable."
Garden centre owners remain confident that there is still growth to be had in the market
Compère for the second day of the HTA catering conference, business consultant Neville Stein, provides a personal perspective on the content:
"Everyone knows that catering has now become a significant revenue driver for most garden centres, and while it is now an established sector of the industry it certainly does not seem to have peaked. It was encouraging to learn that many garden centre operators have either recently invested money into expanding their catering offering or are currently planning to do so — clearly there is a massive amount of confidence from owners that there is still growth to be had in this market.
"Delegates to the conference were challenged by several speakers from outside the industry to develop their food offering. Emma Read, marketing director from Horizons, introduced the conference to some of the new trends in food, and Henry Dimbleby, founder and co-owner of the 33-strong fast food chain Leon, explained his vision for his company, providing fresh, vibrant and exciting food in a fast food format — a challenge but clearly achievable.
"While recognising that new trends could indeed refresh the menu, there was the feeling that the traditional garden centre customer might not yet be ready for quinoa porridge or sushi. Perhaps it is a case of evolution, not revolution, and gradually introduce customers to new menu ideas. Garden centre customers still seem to like the old favourites, so perhaps slowly introduce them to new menu ideas, maybe putting on a daily special that is more imaginative.
"Another strong theme arising at the conference focused on garden centres as a community destination. I quoted Starbucks chief executive Howard Schultz who defined the business as ‘the third place’ — he was suggesting that people need a space other than work and home where they can meet friends, socialise and relax. Perhaps an opportunity here for garden centre cafés to become local community hubs."