'At the moment, gardening is very flower-oriented. We're trying to see garden design as an art form,' he said.
Not surprisingly, this is not impressing the traditionalists. And there will, no doubt, be more than a few sounds of displeasure when his stand is unveiled at the Hampton Court Flower Show on Tuesday. But he is not concerned.
As well as running his own garden design company in Henley-on-Thames, he has - with landscape architect, Debbie Roberts, and Fiona Harrison, a botanist-turned-garden designer - set up the Oxford College of Garden Design to spread the word. 'I have something to say that I think is relevant. The standard of British garden design is at an all-time low,' he said.
Since opening for business last year the college has trained 40 people from a variety of backgrounds and countries in what Mr Heather calls the 'new classicism'. There are two courses - an intensive four- week programme aimed at students from the United States and mainland Europe, and a full-year diploma that has attracted many people keen to move out of such professions as law, accountancy and medicine.
He has been so impressed by the standard of the 17 people seeking the diploma this year that he has put them to work on designing the exhibit that will appear at Hampton Court. 'It's putting into practice what they have learned,' he said.
But this is not the only practical aspect. The courses - which cost pounds 2,646 for the diploma and somewhat less for the intensive programme - also aim to give participants a grounding in the financial side. Mr Heather sees this as an attempt to move away from the 'bored housewife' image of garden design towards training people to be professional - much as has been the case with training courses in many fields in the United States for quite some time.
And though some may find the artistic attitude to gardening pretentious, there is another basic factor behind it. The driving principle is the desire to develop an approach to gardens that is appropriate to the times.
Mr Heather points out that the sharp increase in land prices since the Second World War has made large gardens impractical and unaffordable for most people. As a result, the expansive gardens associated with country houses, such as Sissinghurst, must be replaced by something that works in a small space.
'We're looking at the garden as an outside room. It's still the largest space in most people's homes, and we're trying to educate people in how to use that space,' Mr Heather said.
Part of that involves abandoning the idea that the only important things in gardens are flowers and other plants. To Mr Heather, they are to the garden designer what bricks are to the builder. Extending the analogy, he says he and his colleagues are trying to use architectural principles in gardens.
But this is not so revolutionary, after all; gardens have traditionally been laid out according to geometric principles.