The blue blossom seed is used in the Herblore Habitat. 54 Farming is needed to plant it in a vine flower patch. It will provide 52 xp for planting and 255 xp for harvesting. They can be bought from Papa Mambo in the Herblore Habitat area for 50 coins.
The Blue blossom seeds grow into blue vine flowers. Approximate time from planting the seed to being able to pick the blossom is 20 minutes.
When planted, certain jadinkos will be attracted to it (along with other plants that are required for that certain jadinko) and will show up in that area. Once the jadinko is in the area, it can then be hunted, depending which kind of jadinko it is (by either tracking with a noose wand or box trapping with a Marasamaw plant).