Domoney will help to judge a competition at the college in Yorkshire on 21 January. Around 100 students will create garden designs that will be graded for coursework.
He will be joined by RHS director Jim Gardiner for the design-and-build Horticultural Skills Challenge, said the college's section leader for horticulture David Campbell. "We are going from strength to strength with recruitment in further and higher education as well as very high success and destinations rates," he added.
Higher-education courses have enjoyed a fourfold increase in uptake while further education is up slightly on last year, said Campbell.
Courses range from level 2 diplomas for 16-18-year-old students to a level 6 BSc honours degree in horticulture for undergraduates.
"Askham Bryan is the fastest growing land-based college of its kind in the country," added Campbell. "We have around 150 students of horticulture and aim to double that in three years."
A £34m expansion plan will take student numbers across horticulture, agriculture and equine and animal care from 2,000 to 5,000.
"These are massive plans and it's my objective to ensure horticulture doesn't get swept away but stays as a prominent reason for this college being open," he added.
"Horticulture won't get out of this mess by itself, we have to stand up and be counted - and people like Domoney and Gardiner are great for raising profile."