Snape grass seed

A snape grass seed is a Farming seed from which snape grass can be grown. It can be protected by paying a farmer 15 dwellberries. It can be pickpocketed from gnomes, elves, and dwarf traders, or gained through Herblore Habitat. You need 3 seeds.

Can someone add in things here such as:

amount of XP per harvest of the final product as well as the planting XP

possible minimums and maximums of amount you an harvest (if more than one)

Also, can these seeds be gotten from the master farmer?