In the game, Plunderseeds spawn in the Everfree Forest. They cover from a 1x1 area to 4x4 area.
After starting the Tree of Harmony Story Event, Plunderseed Vines will also appear in other locations after expanding, except for the Crystal Empire, Changeling Kingdom and Klugetown. They will also not affect newer buildings.
In order to clear them,you need 2~5 Element Shards or also 200-10000 .They have the same habits as Parasprites ,Vampire Fruit Bats and Changelings.Tap on them to defeat them. (Plunderseeds often spawn when you expand.)
Clearing plunder vines has more chance of bits then gems as a reward. There is also a small chance that a single gem may pop out at the end.