Bull Kelp can be picked to obtain Kelp Fronds. It then takes 3 full Days to regrow. When picked on the beach, it additionally yields a Bull Kelp Stalk.
Bull Kelp can be pushed towards the mainland with a boat to pick it from any coast without first sailing out. Picking it like that will yield the same results as picking it while on a boat, it does not count as beached.
The Bull Kelp Stalk is obtained by picking a beached Bull Kelp plant. It can both be planted in the Ocean to create a new Bull Kelp plant (this feature is not fully functional as of the Turn of Tides update) and be deployed as a Weapon. It is used as a whip and has the same damage value and extended melee range as the Tail o' Three Cats.
As the Bull Kelp Stalk not only has a limited durability, but also perishes slowly over time and can be stacked in the Inventory. Bull Kelp Stalks can also be used as a mediocre Fuel material for Fire.
Each attack reduce the freshness by a random amount between 2 to 4%. When Bull Kelp Stalk freshness is below 50% each attack has 10% chance to destroy Bull Kelp Stalk. Below 2% freshness chance go to 30%.