When the leaves of deciduous shrubs turn yellow or the needles turn brown on an evergreen shrub, it’s natural to be concerned that the shrub may be dying. What looks like an ailment may really be a natural cycle of growth, like evergreens that will naturally lose some needles on the inner branches, or may be something that can be fixed.
Established shrubs (about three years in the ground) can usually survive with only rainwater, but if it has not rained in over two weeks, shrubs not drought-hardy will begin to suffer. Leaves or needles can turn color or fall off. If the ground is dry more than 2 inches below ground level, then water is needed. Pour about two gallons of water around the base of shrub. Repeat every seven to 10 days if it does not rain. Though more leaves or needles may fall, the life of the shrub may be saved. Prune at the appropriate time to remove any branches that do not respond.
Too much water can be an issue. The shrub may have been planted in an area that does not drain well. If the ground around the shrub is very soft or oozes water as you walk, it is too wet. Installing a French drain to redirect water away from the shrub can help. Moving the shrub to a well-drained location is advisable.
If the shrub is a shade or partial shade variety, like azalea or hydrangea, too much sun can cause the leaves to droop. When too much sun is the problem, the shrub needs to be moved, but wait until the fall or spring to transplant the shrub. In the meantime, water more often and apply 2 to 3 inches of mulch, like wood chips leaf mold, to help retain moisture.
If the shrub is near the street in an area where snow plows are used, salt or other chemicals may be hitting the shrub. Hose the shrub to clean it off and to dilute the chemicals in the soil.
Pests and disease
Extended periods of moisture on the leaves can cause bacterial or fungal disease that can display as black spots or white powdery areas. Snip of the diseased limbs at least 6 inches into healthy wood. Apply a commercial fungicide spray. Extensive pruning to thin the shrub or other foliage in the area to allow more airflow may help.
Insects, like tiny white aphids, may have attacked the shrub. Cut out infected areas. Apply a commercial pesticide spray.
Animals or human contributions
Make sure animals do not use the area by the shrub for a restroom. If you are applying fertilizer to the shrub, stop. Apply fertilizer only on healthy shrubs and according to the manufacturer’s instructions.