Waitrose horticulture buyer Emma Coupe says she is open to approaches from suppliers as the supermarket continues to roll out its garden offer in pursuit of 10 per cent of the market by 2016.
The range launched in 40 pods outside stores in 2013 but is in 140 for 2014 and could reach almost all 300 stores by the end of the year.
Coupe, a former buyer at Wyevale, Homebase and Crocus, said: "Just approach the team. We're aiming for this to be a British-grown proposition. We've looked for best in class and for scale, and have had a successful big formal element with formal topiary.
"We're looking to offer edited choice. Our point of difference is guaranteed performance in the garden. We have limited space so products must work hard, the same as customers who don't have massive gardens."
The 200 plant lines must turn quickly, she added. There are also 200 hard goods gardening lines.
Waitrose will introduce a 16-plant cut-flower herbaceous range from Farplants later this month and autumn fruit tree, wildlife, bird and tree ranges this autumn.
Coupe said Waitrose is committing up to 2017 and is "going to settle at 90 per cent UK-grown". Tracey Telford is grow your own buyer, Nicky Ford is compost buyer and Victoria Mason is cut your own buyer.
Alan Titchmarsh's name is on a new grow your own range and a peat-free compost from Westland. Product development manager Chris Wood said the range will not go indoors in Waitrose.
He said Waitrose "is about quality, not price" and "long-term" crops such as strawberries are doing better than single-season ones like potatoes. Ten per cent of the UK garden retail market is "feasible", he added. "Customers are responding positively."
Waitrose cut flowers are 40-60 per cent British, fluctuating through the year, he said. Finlays is a supplier, Butters is main middleman for gardening products and Bransford Webbs is another grower for the supermarket.
Titchmarsh on TV - Love Your Garden scheduled for fourth series
The face of Waitrose gardening, Alan Titchmarsh, will return to ITV from 24 June. "Love Your Garden is back for a fourth series," he confirmed. "ITV don't want it to be the last - they want it to be on in 2015 as well but I'm taking it year by year."
He added: "I've filmed at Buckingham Palace since last autumn with Oxford Scientific Films for two one-hour ITV shows on the garden's natural history, plants and flowers. It's an oasis in central London and not just an outdoor function room like people think. It's full of fungi, birds and wildlife - a sanctuary in the middle of the city.
"This summer I'm filming Britain's Best Gardens for summer 2015 broadcast on ITV to try and find 30 of the best gardens in the country."