The seeds will grow into seedlings within five to fifteen minutes.
Orange tree seeds may be grown into a orange tree which gives oranges. You must have level 39 Farming to plant it. Planting an orange tree sapling gives 35 farming experience. A healthy orange tree, when checked, provides 2, farming experience.
To plant it, you will need to put it into a plant pot and water with a watering can to turn it into a orange sapling. Ogres, Moss giants, Aberrant spectres, and Dagannoths are a few examples of monsters with good seed drops. Catching implings, especially Nature implings. Watermelon seeds can be obtained as a reward in the Temple Trekking minigame.
Seaweed spores spawn randomly in the Fossil Island underwater area. Orange tree seeds may be grown into a orange tree which gives Oranges. You must have level 39 Farming to plant it; planting it gives you Farming experience.
To plant it, you will need to put it into a Plant Pot and water with a Watering can to turn it into a Orange sapling. Then you can put it into a fruit tree patch with a Gardening trowel%. Aquanites drop yews and a few fruit tree seeds.
I don't know anything about monsters dropping those kinds of seeds, but I know Coeden sells a decent stock of those seedlings. Nests from kingdom or woodcutting also offer the seeds that you mentioned. The Orange tree must be grown with the Farming skill. Level 39 farmers may plant an orange tree seed in a plant pot that has been filled with dirt from any empty gardening patch. A gardening trowel is needed to plant the seed, then it must be watered. The potted plant will become an Orange seedling.
This action is all performed in the inventory or backpack section of the screen. After