Nicholas Marshall said the growth of the 119-centre group was "plant-led" through the core business of nursery stock and bedding.
The company also moved HQ from Slough to Syon Park in west London this month. Marshall said: "How many people go to work in a Capability Brown landscape? Our tails are up. We're thrilled with the new offices."
But the group has also been on the receiving end of a £30,000 fine, after a health and safety prosecution at its Chilton centre.
"It is ridiculous. We've only had three accidents in 10 years at that centre. How do you avoid elderly people falling over? This is a storm in a teacup.
"We have high standards of health and safety - probably higher than any garden centre in Britain. But in the end if you're going to allow 80-year-olds into a garden centre, sooner or later someone will fall down."
He said the cost to Vale of White Horse District Council of convicting the company of one count of failing to discharge its duty under the Health & Safety at Work Act was huge and that the council had 23 accidents in the last year on its own premises.