Unigro's plant reception and quarantine unit will replace Kew's existing facility, built in 1979. The new unit means that Kew can keep its rare and interesting plants safe from pests and diseases.
The plant reception and quarantine unit will initially be used for plants entering and leaving Kew. However, later on a quarantine service will be provided to a range of organisations.
Invasive species cost the UK economy £1.7bn a year. Kew chief executive officer Professor Stephen Hopper said: "Investing in quarantine is vitally important."