Alnwick Garden created a stir when the first phase opened in 2001, and the development of the Northumberland attraction continues. Plans include extending the cascade up to the entrance, while the larger lawn area will be replaced with a spiral garden on a huge mound, which will give views across the garden and the landscape beyond.
A sensory garden is also in the works and an adventure playground underneath the giant tree house is being designed with wheelchair users in mind. "It will cost £25m to £30m to complete," says Jones of the next phase. "The aim is to complete it in the next five years, but that all depends on funding."
The Duchess of Northumberland, who lives in the adjacent Alnwick Castle, was the driving force behind the garden's creation and is "still the leading light", according to Jones.
Belgian father-and-son landscaping team Jacques and Peter Wirtz will again be brought in to design the next phase, having been selected over British designers such as Dominic Cole for the garden's original design, which was planted with mostly Dutch stock. "I am keen to source locally now," adds Jones.
Just keeping the existing garden in tip-top condition is a challenge, he says. "At Threave (the National Trust for Scotland garden where he worked before Alnwick) there were 50,000 visitors a year. Here there are 10 times that - the wear and tear is phenomenal."
Jones has been at Alnwick two-and-a-half years and manages 10 gardening staff, ranging from ex-miners to teenagers. "We all muck in," he says. "If a member of the public asks a question, you put down your tools and engage with them. If you can't answer their question, you find someone who can.
"As a result, we get most of our work done between 7.30 and 10am, before it opens. But it's still part of the job." Lack of reserve plant space is an issue though. "We have a small Victorian glasshouse that we struggle with, though there is a new glasshouse in the masterplan," explains Jones.
"Horticulturally, my biggest worry is box blight. We have a lot of box hedging, but we may have to take it out and put in something else. Much of our time is taken up with hedge cutting and pleaching, but we also have quirky things like cannabis to deal with."
A children's favourite, the Poison Garden attracted the wrong sort of interest shortly after it opened, when six cannabis plants were stolen. This and narcotic plants are kept in wire cloches in the garden, which under the terms of a Home Office licence is kept locked except during guided tours.
A book for teenagers, The Poison Diaries, adapted from an idea by the Duchess and set partly in the Poison Garden, will be published in July. "There will be a huge response to that," Jones predicts.
The Poison Garden enables Alnwick Garden Trust to broaden its educational offering, he explains. Performances by actors playing drug addicts have featured during school visits, which Jones describes as "very hard-hitting".
Even areas such as the water sculptures are intended to impart knowledge, such as explanations of topics such as surface tension. "But children like to get wet too," says Jones. Indeed, water is employed at almost every turn in the garden and Alnwick employs two full-time water engineers.
More organised learning in the garden comes through its Roots and Shoots programme. "We work with 10 schools from deprived areas," says Jones. "Each school has its own allotment and they come in four times a year to plant, prick out and finally harvest vegetables, from which the chef makes soup. Hopefully they then get inspired to do something similar back in the school grounds.
"It's been very popular and successful - even very young children can fill a pot with compost and plant a runner bean seed in it. Everyone takes something away with them."
Older members of the community are also engaged through the Elderberries club for over-50s, which runs activities such as tea dances and "salsacise" or t'ai chi classes in the garden, and is even co-ordinating a "knitted garden" replica in wool. "We don't want people to be isolated," says Jones.
Events and education teams ensure the garden is rarely left idle. String quartets and mime artists "almost use the garden as a theatre", he says, while a full programme of weddings and functions helps with generating revenue.
The recruitment of former Disneyland Paris head Christian Perdrier as chief executive of both castle and garden last October signalled a move to promote the town and its attractions more concertedly. "Christian is keen to make Alnwick a destination," says Jones. Visitors can already buy a two-day ticket for garden and castle and staff are trained to work at both. But he concedes: "There has been some opposition from locals, who liked it being a sleepy little town."
1975-77: Apprenticeship, Peterborough City Council
1977-80: Landscape design and construction course, Merrist Wood
1980-83: Landscaping company, London
1983-89: Garden instructor, National Trust for Scotland's Threave Garden - while also running own garden design and build company
1989-95: Set up horticultural department, Barony College, Dumfries
1995-2007: Principal, Threave Garden
2007 to date: Head gardener, Alnwick Garden