Southern Magnolia Salt Tolerance

Salt Spray Tolerance

• Salt spray, which is carried inland by sea breezes, can be harmful to many plants. Southern magnolia can be used in locations near the ocean but does best when set back from the beach. It's not suitable in the blowing sands and excessive salt spray of direct beachfront locations. Its thick, evergreen leaves are moderately resistant to indirect salt spray, but the tree should be sheltered from the oceanfront by more salt-tolerant plants, buildings, fences or sand dunes.

Soil Conditions

• Salt accumulates in soil through salt spray, flooding or seepage of sea water, the use of de-icing road salt or excessive use of fertilizers. Southern magnolia has relatively good tolerance to salty soils and you can grow it in poor, sandy soils if it has enough room for its roots to spread and you properly irrigate it. However, this tree thrives in moist, acidic, well-drained locations and does not tolerate excessively dry, alkaline soils. It can tolerate areas that occasionally flood, but cannot withstand long periods of submersion or soggy soils.

Detecting Salt Damage

• Damage from salt spray appears as scorched, brown or disfigured leaves. Sometimes salt-laden water droplets dry and form a visible white crust on leaves. Damage from salty soil takes longer to detect and includes stunted growth, fewer or smaller flowers, leaf drop, dead branches and sometimes tree death. In evergreen trees such as Southern magnolia, damage from saline soil usually first becomes evident in winter or early spring when new growth appears.

Reducing Salt Damage

• Aside from planting your Southern magnolia in a sheltered spot, you can reduce damage from salt spray by using an overhead irrigation system to wash salt off the leaves. If excessive salt exposure occurs, such as after a storm, flush the soil by applying 2 inches of water for two to three hours or until runoff occurs. This process should be repeated every few days until salt levels are reduced. Soil salinity can be determined though laboratory testing of soil samples or field tests. Less frequent but deep watering also helps reduce salt buildup in soil. The use of organic mulch around the base of the tree helps retain soil moisture and protect the soil from salt accumulation.