Salveyo weed (Japanese: アシレ水草 Ashire water herb) is a type of herbal medicine found exclusively in the anime. It only grows on clear lake bottoms and can be used to cure paralysis. Poliwag are known to eat this weed. Misty used it to cure Ash and Tracey of a Vileplume's Stun Spore in The Stun Spore Detour, with the help of a friendly Poliwag.
Meanwhile, Jessie had also been a victim of Stun Spore, and James and Meowth also tried to locate the Salveyo weed to help cure her. They tried to steal it from Misty using a variety of techniques, including battling, trying to lure her with dresses, perfume and food, and even dressing up as a woman and her child. In the end, Misty just gave some of the weed to them since she realized all they wanted was to make Jessie better.
Later, in Whichever Way the Wind Blows, Meowth used a medicine made from Salveyo weed in order to cure Jessie and James of the status caused by Vileplume's Stun Spore.