Plant it to grow Ghost Jar. Place this jar down and it will suck in a ghost that's above it. You will probably need some friends with Neutron Guns to keep the ghost contained or it will escape! A jar takes 2 seconds to activate, and then only collects spirits for 5 seconds, so time it carefully.
Ghost Jar Seed price in Growtopia: sells for about 2/WL, buyers pay about 3/WL (median of 442 offers from community Discords, past 30 days). Live price chart and the latest buy and sell offers.
Recently sold at: LKARD, GINAJAR2, ACALOPTIPEN, HZOVX, TI84