The move will see Yorkshire-based Baarda marketing its produce with Huntingdon-based the Greenery UK, which also markets several other UK-grown tomatoes including those grown by British Sugar's Cornerways Nursery.
The Greenery UK is a subsidiary of the Greenery BV, which is owned by more than 1,000 Dutch growers through a co-operative.
It said the agreement had been reached with the support of John Baarda's bank HSBC, which will be providing finance and participating in the refinancing of the company, subject to final agreement.
John Baarda grows tomatoes year round after investing in a £14m facility five years ago. This allows it to heat its glasshouses from a fertiliser company's by-products — steam and carbon dioxide.
David Baarda said: "This development [with the Greenery UK] will allow us to focus on growing and the further development of the nursery at Billingham. It is now about creating a model that would allow the asset to grow towards the original vision.
"Entering into a partnership with a strong industry player like the Greenery UK is very exciting for the future of our business."
The Greenery UK managing director Kevin Doran said: "We are delighted to have one of Britain's pre-eminent producers join the Greenery group. It is a very good strategic fit for our business." A final agreement is expected to be made by the end of the month.