Irish champion Jennifer Reilly, who is studying at Warrenstown College, will be travelling back specially for the final from her work placement in the US. She beat Valerie Orr, a student at Greenmount College, in a tense and exciting regional heat.
Writtle Student James Hearsum, a third-year BSc horticulture student, won the eastern region heat.
Hearsum said: "This competition is just one example of how the industry is very good at supporting people early in their careers. It's a great opportunity for all young people in horticulture and I look forward to a challenging national final."
For the second year running, a Sparsholt College student won the South West regional final - 17-year-old Ross Tapley, who is studying to obtain a National Diploma in horticulture.
Out of 120 Scottish entrants, Adam Bowley from the Royal Botanic Garden Edinburgh triumphed. He is in the final year of his HND in horticulture with plantmanship.
Kew Diploma student Alex Summers, who has a degree in zoology and has worked at Cambridge University Botanic Garden, took first place in the final in the South East.
Gardener Faye Steer was able to benefit from the new online system which means people under 30 not studying at colleges can take part in the competition. Her initial heat was conducted over the telephone, while viewing images online. She won the West Midlands and South Wales regional final, held at Pershore College.
Sally Johnson, a foundation-degree student at Askham Bryan College, won the northern regional final at Sheffield Botanical Gardens. The North West and North Wales final is later this month.
Sponsors are the Shropshire Horticultural Society's Percy Thrower Trust, the HDC, MorePeople and Rollins Bulldog Tools.