Stress is the most common cause of brown tips on houseplants. There are different causes for such stress, but when plants are not receiving adequate care, or are lacking certain nutrients and have others in excess one common outward sign of such stress is brown leaf tips. Brown leaf tips aren't usually a sign of disease or any life-threatening problem for the plant.
Soluble salts are a very common cause of plant stress and brown leaf tips. The salts accumulate in the soil, and while some plants are more sensitive than others -- spider plants, for example -- salts are not beneficial to plant roots and overall plant health. Most soluble salts are deposited in the soil from tap water. It's possible to detect them by examining the pot for a ring of white around the inside edge, or crusty white deposits on the soil surface. The cure for salt damage is to water plants with filtered water and to leach salts from the soil every four to six months, as Texas A&M University recommends.
Fluoride is an additive in tap water intended to protect teeth, but it also inhibits water uptake in plants, according to George Weigel, of PennLive.com. And of course, one sign of impaired water uptake is brown tips on the leaves. Again, the best cure for this problem is to water your plants with filtered water.
There is also the chance that improper watering has damaged the roots and stressed the plant. Most people overwater their houseplants, imagining that they need more care than they really do, while others underwater them. Inconsistent or improper watering damages the root system and causes brown tips on the leaves. Water houseplants when the top inch of soil is dry. Water until water comes out the drainage holes and drain that water from the dish underneath the plant. It's not a good idea to let a plant sit in water.