Buy OSRS Dragonfruit tree seed
The dragonfruit tree seed is the highest level fruit tree seed in Old School RuneScape. You need level 81 Farming to use it. Plant the seed in a plant pot of soil to grow a dragonfruit seedling. The seedling grows into a sapling, which you can plant in a fruit tree patch. The sapling then grows into a dragonfruit tree.
This seed gives great Farming experience. Planting the sapling gives 140 experience. Checking the tree's health gives 17,335 experience. Harvesting the six dragonfruit gives 420 more. That adds up to 17,895 experience per seed. You can earn even more if you come back after the fruits regrow.
The tree takes six growth cycles of 160 minutes each, which is 16 hours in total. Most trees are fully grown within 24 hours. A nearby gardener will protect your growing tree if you pay 15 coconuts.
These seeds are rare drops from bird nests, Farming Guild contracts, and bosses like Vorkath, Hespori, and the Alchemical Hydra. You can also use one seed on the Tangleroot pet to change how it looks.