APL members will be able to submit entries, without charge, for the new category at the show, which runs from 3 to 8 July.
The design category will look for High Impact, Low Cost gardens or garden areas.
"This aims to showcase a practical approach to gardens that also provide a wow factor," said APL.
"Visitors will be able to recreate the garden design, based on a fixed budget for hard landscaping, plant material and labour."
Four gardens will be chosen to show what can be achieved for budgets of £5,000, £7,000, £10,000 and £13,000. The design can be any size and shape between 30 to 50sq m and reflect any part of the garden or a small garden.
APL chairman and RHS show exhibitor Mark Gregory said:
"This is a fantastic opportunity to show off great garden design and landscaping on a fixed budgets. There is sure to be great interest and ‘takeaway’ appeal."