There is a huge sugar pumpkin crop within Iron Marches at Victium Moors, as indicated by the map below provided by Tukijaaliwa.
. Just to give you an idea here is a small picture of the crop.
Also found in a patch in Bloodtide Coast. SSE of the Loin's Arch entrance. Between Remanda Saltmarsh and Lostwreck Waypoints. Top of the Jungle troll fort, the entrance is on the north side. Got 15 on my 1st picking.
gathered in Iron Marchesnortheast of Bulwark waypoint (west)west of Invictus Castrum
Picture for this: