Buy RS3 Rosemary seed
The Rosemary seed is a Farming seed in RuneScape 3. You plant it in a flower patch. You need level 11 Farming to plant it. One seed fills a whole patch.
Rosemary grows fast. It takes only 20 minutes to finish, in four stages of five minutes each. Planting one seed gives 12 Farming experience. Harvesting gives 66.5 experience. Each patch gives 3 rosemary at level 11. You can get 6 at level 35, 9 at level 55, and 12 at level 65.
The main reason players want this seed is crop protection. A fully grown rosemary plant keeps cabbages in nearby allotment patches safe from disease. This makes it a smart pick for cheap Farming training runs. There is no payment option to protect the rosemary itself.
The harvested rosemary is useful too. Players use it to make dense honeycombs and imp repellent. It also works in compost bins and troughs on the player-owned farm.
The seed is stackable and tradeable, and it weighs nothing. You can plant it at flower patches south of Falador, north of Catherby, north of Ardougne, and west of Port Phasmatys.