Co-owner Andrew Cardy said planning permission was being sought to turn 2,500sq m of redundant glasshouse into retail space and to change the "B" retail nursery rating, which restricted it to selling own-grown products, to an "A1" retail rating, which would enable it to stock a broader range of products and compete with nearby garden centres.
The nursery was recently re-rated as a garden centre, which led to rates rising from £1,200 to £22,000. Cardy said: "We've been re-rated but they haven't changed what we can sell."
He added: "It's crucially important we get that change. The product range we currently stock we're not allowed to sell - even though we have done so for more than 10 years."
They were also appealing against the farm shop restriction to sell only produce from within a 16km radius, as well as seeking permission to increase the restaurant's seating level from 35 to at least 65.
The site's farm shop was forced to relocate from across the road after the landlord, Wyevale Garden Centres, terminated its lease in late 2006. The two businesses opted to merge on the nursery site and planning permission for the farm shop and coffee shop was lodged but has led to ongoing planning issues.
Cardy said the investments made on the site since the last year's relaunch were beginning to bear fruit with sales up 50 per cent for the year so far - having doubled in February.