Rosemary plants are hardy and able to withstand many adverse conditions, including freezing weather and short periods of drought. It is possible to revive dried-out rosemary plants, depending on the overall condition of the plant.
Check the ends of the branches to determine the extent of damage. If the branches are thoroughly dried out, check the base of the trunk and roots. The rosemary plant needs to be replaced if the trunk or roots are dry and brittle.
If the plant is salvageable, carefully remove dried and dead leaves from it. Using a pair of sharp garden shears, trim the branches to remove all dried areas, without cutting into the live branches.
Thoroughly water the rosemary plant and provide plenty of natural light. Water outdoor plants at their base until the soil is thoroughly moist. For container-grown rosemary, fill the container with fresh water and allow the soil to absorb the water. Repeat this several times, until the soil retains the moisture.