The grand seed pod is a single-use teleport item that can be obtained as a rare reward from Wingstone, Penwie, Brambickle and Professor Manglethorp in the Gnome Restaurant minigame. Seed pods are stackable. They can take players to the Grand Tree, and have two right-click options: launch and squash.
A player squashing the seed pod.
Launching the seed pod will take players to the top floor of the Grand Tree, by means of Captain Lamdoo and a glider, but can only be used outdoors. This option will also give the player 100 Farming experience. Squashing the seed will take players to the Grand Tree (to the ground floor by King Narnode Shareen) faster than Launching it, but the Farming experience will not be given, and their Farming level will be temporarily drained by 5 levels. Neither method can be used past level 30 Wilderness.
The upgraded version of this item, the Royal seed pod, is obtained upon completion of Monkey Madness II, and has unlimited charges.
This item is commonly used to lure players. Most of these lures involve the victim dropping valuable items then proceeding to Squash or Launch the pod.
For an exhaustive list of all known sources for this item, see here