This very drought-stressed peace lily (Spathiphyllum) really needs a good soaking! Source: http://www.kiwicare.co.nz
You return from a trip to find one or two houseplants completely wilted, their stems bent and floppy and their leaves dripping to the ground? That’s because they suffered a serious lack of water during your absence.
When this happens, the potting mix often pulls away from the wall of the pot. So, when you water to try and save the plant, almost all the water flows into the saucer instead of penetrating the rootball and the poor plant actually gets very little.
In such cases, plain “watering from above” as usual is not enough. Instead, immerse the pot in water—completely!—and let the plant soak for 2 or 3 hours until the soil and the plant are completely rehydrated. You can immerse the rootball in a sink full of water, in a bathtub, in a bucket, even in the toilet bowl (been there, done that!): that’s of no importance.
When the plant has recovered, let the rootball drain thoroughly and put it back in its saucer. And if the rootball still remains pulled back from the pot edge, comprising future waterings, fill in the empty space with fresh potting soil.
Of course, if the plant lacked water for too long, your efforts may be in vain and it will die, but in most cases, it will recover very quickly and can go on to live a happy life.
Note that allowing a plant to nearly die from lack of water is not good for it. Try not to repeat this scenario too often!