WATCH: Video of the fire from neighbour Julie Wilkin
Dozens of firefighters have been called to a garden centre just south of Dereham.
The incident at Toftwood Garden Centre started just after 3pm.
Neighbour Julie Wilkin said: "We live next door to the nursery and we heard a bang, before we were aware of the fire."
Ten fire engines have been called to deal with the fire, which has closed the A1075.
It has been shut between School Lane in Dereham and Letton Road in Shipdham and police have advised drivers to avoid the area.