There’s a 冬(东)瓜 (Wintermelon/”East Melon”), a 南瓜 (Pumpkin/”South Melon”), 西瓜 (Watermelon/”West Melon”), but nobody seems to know what a 北瓜 (”North Melon”) is.
Turns out that there actually is such a thing, with a latin name of Cucurbita Pepo. Beyond that, I couldn’t find much information or a reliable depiction of the mysterious melon. Suffice it to say that North Melons simply aren’t that popular.
Also, a fun observation: all three melons also represent separate seasons, in the reverse order.