Wisteria
The only flowers that the moon gladiators will water are wisteria.
The moon gladiators have a thing for wisterias.
とう, どう
ふじ
None
Since they're on the moon, where did they get the wisteria from? Actually, from one of the points on earth that is nearest to the moon, Mt. Fuji (ふじ).
Imagine them reaching down from the moon and plucking some wisteria up from Mt. Fuji then taking them back up to the moon. Now they water them.