While the packing workers tidy the coolroom before heading home, banker-turned-farmer William Pham gestures at the rows of hydroponic basil in front of him. ''We recycle our water, so we need one-sixteenth of the water for conventionally grown basil,'' he says.

Together with business partner Jan Vydra and their 60 casual and full-time staff, Mr Pham produces and packages 70,000 bunches of herbs weekly. They began operations here in 2008, but their farm was included in the revised urban growth boundary in 2010. They're looking for land elsewhere. ''When we bought here, this road was empty,'' Mr Pham says. ''Now you can't recognise it.''

Mr Vydra, recently named the 2011 Young Australian Farmer of the Year, says he wants to stay within 40 minutes of the city. That kind of proximity is better for business: it's easier to find workers, supplies are cheaper and more accessible, and the cost of transporting produce lower.

But once the boundary expands, property values rise and rates increase. ''That's what happens - you have to sell up. It's beautiful soil around the whole area at Clyde. People have been farming it for 100 years and they have to move,'' he says.

''There's an economic benefit - we get much more money for our property - but as a community, we lose some really fertile soil and they're going to put slabs on top of it.''

Although he can see the dilemma for planners, who want to provide affordable housing, he's worried about food security as older farmers retire. ''We need to figure out what's being produced here and how we're going to shift it elsewhere to make sure we keep producing food for our people.''

Mr Pham is ambivalent about the change. He says small-time farmers will disappear, but doesn't think there will be any impact on shoppers. ''A lot of the smaller growers will sell up, make their money and have an easier lifestyle. We spent a lot of money on this place, so what the heck, we may as well do it again. We're too young to retire. We just have to move further out.''