Biomass Seeds can only be planted on Creep Blocks and only when germinated. To create a Creep Block, simply place one soul sand down and right click the top with a Creep Ball. Next, you need to place the Biomass seed in an Altar of Blood with a Blood Crucible one block apart from the altar with 10 blood in. Place the seed in and press "germinate". Right click the top of the Creep Block with any type of Glaive and plant the Biomass seed in it. To speed up growth you can right click the top of the Creep Block again with Blood from an Essence Vessel or an Essence Keeper with at least 1 "point" of blood in it. After 20 to 180 seconds the Biomass Seed will grow a stage. The three stages are planted, stem, flowering, and bloom. When at the fourth stage harvest the Biomass Seed to get 1 Biomass and 1 Biomass Seed. You'll have to re-germinate the seed again after harvest.
- The last stage takes two to ten minutes to grow when using blood.