Often when a plant begins to fail, people assume it must be because it's infested with pests or has acquired a disease. These are common problems which do cause many plants to die, but brown leaf edges are not a symptom of these problems. Brown leaf edges mean a plant is stressed. If you see brown leaf edges, look for common plant stressors.
Determine if the plant with brown leaf edges is receiving enough water. If the plant is living outdoors, monitor the soil over a period of several days. If it seems to be dry for long periods, supplement the natural rainfall with frequent waterings. Most house plants must be watered once per week.
Check to see if the plant is root-bound. When the roots of a plant fill a container, they begin to wrap their roots around the bottom and sides of the container. When this happens, they cannot bring in a sufficient supply of water. Giving the plant more water helps, but a better long-term solution is to repot the plant into a bigger container.
See if the soil adequately holds water. Look at the soil to see if it contains a large amount of sand, rocks or perlite. These materials create a porous soil, which allows water to quickly drain. This is ideal for cacti a succulents, but other plants cannot get an adequate supply of water before it drains.
Look at the roots to see if they are damaged. Root damage can cause a disruption in water supply and therefore brown leaf edges. If roots are rotting, the plant has likely been overwatered. Determine the cause of the root damage and prevent if from happening again to save the plant.
Reduce fertilization. When water is eliminated as a possible source of plant stress and cause of brown leaf edges, the plant is usually being overfertilized. Synthetic fertilizers cause a build-up of salt in the soil, which cause plant stress.