Kelp is an underwater plant that can be found in ocean biomes, often growing in large groups called kelp forests. Players can harvest it by breaking the plant at any level, which yields kelp items that can be smelted into dried kelp, a food source. Additionally, kelp blocks can be crafted from nine dried kelp pieces and used as building material or fuel in furnaces. Its rapid growth rate makes it a renewable resource.
This item has no numerical item ID, therefore you must use the item ID to spawn the item. Numerical item IDs were removed in Minecraft version 1.13.
The item id for Kelp is minecraft:kelp
The item ID for Kelp is minecraft:kelp
This is the spawn command to give yourself Kelp in Minecraft which includes the Minecraft /give command. If you are using the Essentials plugin you will need to use /minecraft:give instead of /give