Idverde acquired The Landscape Group in March last year. Quadron has 700 staff and a turnover of £30m, bringing idverde's turnover in the UK to £90million, with 1600 staff.
A statement from idverde UK said the transaction "reinforces the group's geographical networks in the UK and strengthens its commercial position in key locations including Greater London and Birmingham".
Merging two BALI award-winning companies would also enhance the company's reputation, it added.
Nick Temple-Heald, chief executive of idverde UK, said: "Bringing together Quadron and The Landscape Group as sister companies within idverde UK is the perfect outcome of our plan to grow the idverde UK business. Our two businesses are both green specialists and passionate about the importance of parks and green spaces in the lives of the British people.
"We have always respected and admired Quadron for their strong client relationships and innovation in community engagement. Our two management teams are looking forward to working together to create even better value for our customers and wonderful career opportunities for all our staff."
Hervé Lançon, president of the idverde group added: "With this acquisition, we're proud to demonstrate that idverde is leading the development of the green services market in the UK. With this significant leap forward, we hope that idverde will become the partner of choice for both public and private sector customers in the UK, just like it is today in France."
The Quadron acquisition is the latest in idverde's UK and European growth strategy, backed by the significant resources of Paris-based private equity investor Chequers Capital.
Bertrand Rabiller, Chequers Partner said: "We are delighted to support idverde in implementing its strategic development plan for the UK, which began less than one year ago when TLG joined the group. Idverde will benefit greatly from the additional skills, relationships and passion that Quadron offers to the UK's dynamic green service market. This new acquisition is a further step in idverde's Europe-wide development plan."
Clive Ivil, managing director of Quadron, concluded: "We see joining the idverde family as the best possible opportunity to build on Quadron's success, and take it to the next level. I firmly believe that this will allow us to offer both existing and new customers yet more value and innovation, as well as providing stability and opportunity for my Quadron colleagues.
"Joining forces with idverde UK will bring significant benefits to both organisations, including greater geographical coverage, the sharing of best-practice and technology and unrivalled career prospects for all our staff".