Place your finger beneath the surface of the soil and test the material for moisture. Despite the top layer being dry, the soil beneath might still be sufficiently soaked~ This is all assuming that you have already have watered these blooms at least once of course.

[Yuuka remembers you. Mostly for being a bit of an idiot, but she still remembers you.]

Despite all this however, watering flowers can at times require your own judgment. If there has been a dry spell, a water spell would level out the magic as it were.