The actor became interested in the project after befriending the college’s resident blacksmith, Simon Grant Jones.
Fox said he was "honoured" to have been asked to officiate at the event which comprised a tour of the glasshouses and gardens, followed by lunch with college principal Clare Davison, governors, staff and students.
He said: "We will go away from here thinking of the impact of inspiring the young for lifetime occupations and lifetime happiness which you can see is a reality here.
"I thought it would be quite impossible at my age to be inspired again, I realise that at 10.30 this morning this was my point of view about life, I have now completely changed thanks to today."
The £850,000 glasshouse project replaced two outdated existing polytunnels, a non-operational smaller greenhouse built in the 1960s, and dilapidated tool sheds.
The majority of the six month build was funded by a grant from the Skills Funding Agency, together with a "substantial" contribution from the College via its governors.
The new structures will house classrooms, tool stores, learning resources, and growing facilities for students. Their produce will supply the home market and visitor centre with vegetable in both new and heritage varieties, and cut flowers for the British grown flower market.
This build includes sustainable initiatives including rainwater harvesting, automatic shade systems and solar power.
Local architects A&Q Partnership designed the glasshouses, produced by Cambridge HOK and Venlo. Project ground works for both areas have been managed by Kingston Maurward premises and estates manager Kim Payne and stocked and maintained by head gardener, Nigel Hewish and his team.