Murrell's design will now be submitted to the RHS for a chance to have it featured as a show garden at this year's RHS Hampton Court Palace Flower Show.
The award judges said Murrell's winning entry "Go Wild in the City" demonstrated great design principles with a heavy accent on plant choice and associations and was highly commended. They added that it had considerable potential for the Hampton Court show.
Murrell has a background in art, design and horticulture and is now studying a foundation degree in garden design at Sparsholt College in Hampshire.
The award is an initiative launched by Wyevale East Nurseries with the RHS and is aimed at students of horticulture or design at level 3 or above.
Wyevale East Nurseries director Richard McKenna said: "We have many links with horticultural colleges and feel that the students of today are critical to the horticulture industry of tomorrow.
"We received a fantastic response to the competition and the overall quality of submissions was of a very high standard, but Charlotte Murrell's entry shone through. It was well presented with good-quality plans and she had paid close attention to ensure the design fitted her brief."
This year's award judges were McKenna, RHS The Garden editor Chris Young and BALI design membership director Christine Parsons.