Hemp is a strong fibrous plant that can be used for many different things, including strong Rope or Fabric
Hemp seeds, with HCSeeds enabled, can only be obtained from tilling the ground with a hoe; without HCSeeds they drop from tall grass.
These seeds must be planted on hydrated farmland and have plenty of light, be that sunlight or from a Light Block. Growth can also be accelerated by fertilizing the farmland.
Hemp has two stages, it is best to let the plant grow to stage 2 and only harvest the top block, similar to Sugar Cane.
Rustic's ever-fertile soil: -dirt + wonder sap -can't be trampled and doesn't require water -works forever
BWM's planter based fertile farmland: -apply bonemeal to a tiled planter -can't be trampled, doesn't require water and grows faster -works forever
BWM's fertile farmland: -apply fertilizer (requires cauldron) to farmland -grows faster, boost to hemp -requires water and works forever
Pyrotech's mulched farmland: -apply potash mulch (complex recipe) to farmland -can't be trampled, and grows faster -requires water and is temporary