Buy OSRS Seaweed spore
The seaweed spore is a Farming seed in Old School RuneScape. You plant it in the seaweed patch, found in the underwater area of Fossil Island. You need level 23 Farming to grow it.
Each patch takes one spore. The crop takes about 40 minutes to grow, split into four stages of 10 minutes each. Planting gives 19 Farming XP and each harvest gives 21 XP. You can pay Mernia 200 numulites to protect the patch while it grows.
When the crop is done, you harvest giant seaweed. Each patch gives at least three, and often much more with compost and a high Farming level. Ultracompost adds extra harvest lives, and an attas plant in the anima patch boosts the yield.
Players want giant seaweed for two big reasons. First, it gives a good chance at the Tangleroot pet for its short growth time. Second, ironmen use it with the Superglass Make spell to make lots of molten glass for Crafting. Giant seaweed gives far more molten glass than regular seaweed, so these spores are a smart pick for training both Farming and Crafting.