The isuke was a type of plant lifeform from the planet Vulcan, a type of bush plant with gnarled growths and tiny leaves that, like most plant life on Vulcan, was adapted to the hot, dry climate there. Spock thought of the isuke bush when noticing the lush plant life collected in the parklands of Ka'a Beach on Kauai, Hawaii, on Earth. He found it interesting how the water-rich environment allowed for a wide diversity of plants so different from those on his homeworld. (TOS novel: Vulcan's Glory)