A Uthanian scatterbud was, according to the Fourth Doctor, a "very rare", "beautiful red flower" which grew only on Uthe 3. It was, he said, a former symbol of peace on the planet. He once bade K9 Mark II to find such a flower on the surface of the planet. With it, he was able to prove to that world's battle computer that the war it was conducting should end.
Since the computer had asserted that the Rad-Plague had destroyed all life, the existence of any life successfully disputed the computer's logic. K9's found flower thus caused the computer to shut down and the two-century war to finally end. (PROSE: Sweet Flower of Uthe)
Behind the scenes
At different points in the story, scatterbud is capitalised and not capitalised.