Seven men smuggled cocaine, heroin, cannabis, MDMA, amphetamine and firearms in lorries from the continent into the UK.
The National Crime Agency (NCA) said it seized drugs and guns worth £30m.
The men were jailed for between 36 years and 27 months at Preston Crown Court.
The gang was charged with importation offences after four separate seizures in 2014.
Three were made at the Channel Tunnel terminal in Coquelles, France, and one in Accrington, where the flower wholesale firm was based at Albion Mill.
NCA investigators and their Dutch counterparts linked all the importations to head of the group, Dutch national Mohammed Imran Bhegani. 39, and Sajid Osman, 44.
Bhegani had made all the arrangements, getting consignments delivered to premises in Albion Mill, Accrington, which was rented and operated by Osman and Nizami Esshak, 56.
NCA officers raided the unit on 26 August 2014. Taimur Zahid and Hussain Farooq arrived as "customers" to pick up drugs from the unit.
Investigators found three boxes containing flowers and 12 kilos of cannabis in their car.
More than 200 kilos of cannabis was seized from Albion Mill along with notebooks containing details of customers and quantities of drugs to supply.
A gang which used a Lancashire wholesale flower firm as cover for an international drug and gun-running operation has been jailed.