The occasional shower helps counteract the low humidity and indoor heating that’s prevalent in winter, removes dust and dirt that may have accumulated on the leaves, and allows the plant to “breathe” and photosynthesize more efficiently.
It also rinses away any pests and their eggs. (Spider mites, in particular, love to hang out on dusty leaves.) Think of it as a deep cleaning for your houseplants, since hand dusting only removes surface dust (and sometimes, merely smears it around).
If you can’t find a housesitter to come over and water your houseplants, here’s a neat little trick to keep in mind.
Gather all of your plants in the bathtub and drench them with a shower from above. Then, fill the tub with 3 to 6 inches of water (depending on the size of your pots) and cover everything with clear plastic (even a clear plastic shower liner works in a pinch).
This simple setup helps keep up humidity levels and lets the plants wick up water from below, buying you about two weeks of vacation time without worrying about your plants drying out in your absence.