Why is salt used to melt ice on the roads? What would happen to many roadside plants as a result?
Salt is used on roads to melt ice because it forms a solution with water that will not freeze until reaching a lower temperature than clear ice water. Salt can pose problems for roadside plants.
The freezing temperature will depend on the concentration of the salt water solution, how well it stays on the road, as well as the volume of traffic on the road.
This effectiveness of this method of melting ice on roads is limited to areas or days when the temperature is reasonably close to the normal freezing point of water. It will not be effective and so is not used in climates where the temperature is consistently well below the normal freezing point.
There are many problems related to the use of salt on roads, and it does have detrimental effects on many roadside plants. The most common effect is injury or death of some plants. The salt may cause the plant to use up more energy to draw in water through its roots.
Salt can stop some plants from growing near a road by triggering an internal stress hormone in the roots that will turn off root growth.
Other plants can handle the increased salinity at the roadside or adapt to it and can survive without a problem.