The snake plant (Sansevieria spp.) is sometimes called the cast iron plant, with the most commonly grown variety (Sansevieria trifasciata) also called mother-in-law's tongue because of its narrow, erect and sharply pointed leaves. It's usually grown as a houseplant, although it can grow outdoors in U.S. Department of Agriculture plant hardiness zones 10 through 12. Although it's tough and drought-tolerant, this plant's not invincible and could wilt or show other signs of a problem. If this happens, most likely it's been overwatered or is suffering from a heavy pest infestation.
If your snake plant's leaves begin to wilt and fall over, the most likely cause is overwatering. This plant prefers slightly dry soil, especially during the winter when it grows slowly or not at all. Even during spring and summer, when growth is greatest, it's best to wait until the normally glossy leaves look a bit dull before watering, then water the plant thoroughly. If you've overwatered it, it's likely that the roots have begun to rot, a problem that spreads gradually through the entire plant.
If you catch this problem early, when only a few roots are affected, it's possible to save the plant by removing it from its pot or from the ground if it's outdoor-grown. Examine the roots and cut off any that feel soft, using sharp shears to cut behind the affected part and into firm root tissue. Also cut off any affected leaves along with the roots. Wipe blades with rubbing alcohol after each cut to prevent spreading plant disease. Re-plant the snake plant into fresh soil and adjust your watering schedule to prevent a recurrence of the problem.
If you find that all the plant's roots are affected and feel soft, it can't be saved and it's best to discard the plant.
Several pests might infest a snake plant and cause damage that, if uncorrected, could damage its leaves and eventually jeopardize its survival. Mealybugs accumulate in groups on the leaves, forming fluffy white masses. They feed on the leaves and can cause visible damage. Control these by touching each white mass with a cotton swab that's been dipped in rubbing alcohol, wetting it thoroughly to destroy the insects.
A snake plant can also attract spider mites, which aren't visible but cause visible, web-like coverings on leaves. They suck plant juices and can cause extensive damage over time. For a minor problem, use a forceful jet of water aimed at the webs to destroy the pests. If the infestation is widespread, spray the plant with insecticidal soap, diluted at a rate of 5 tablespoons per gallon of water; repeat every two weeks as needed.