Thursday, May 15, 2008

Landscape - Salt Spray Damage From Recent Storm

The recent storms produced salt spray that was blown inland along the coast of the Delaware Bay. Symptoms are just now showing up in plants. The following is information on salt spray damage from Virginia Tech and from UD Extension.

The aerial drift of salt-laden water droplets that are deposited on trees and shrubs causes salt spray damage. When droplets evaporate, the salt's sodium and chlorine ions can penetrate stems, buds and leaves, causing direct damage. Salt spray damage to trees and shrubs is most frequently seen on seaside plants and near sidewalks and roads where de-icing salts are applied. Additional stresses in these areas, including wind, sun, heat, exposure, heavy traffic and saline soils, increase the likelihood of damage.

How does salt spray affect trees and shrubs?

Exposure to salt spray can cause stem and foliage disfigurement, reduced growth, and often plant death. Because aerial salt spray damage may appear similar to damage caused by other stresses, a tree or shrub's location and damage symptoms should be carefully evaluated to correctly identify the damage's cause. Consider the distance from salty water sources and the severity of storms and winds that carry aerial salt drift inland.

Symptoms of salt spray damage

Examine injury patterns on trees and shrubs. On foliage, salt spray causes leaf burn or scorch, or needle browning. Direct signs such as white salt residue are a strong indication that salt spray may be injuring landscape plants. For seashore areas, salt spray damage is seen soon after storms, and occurs inland if salt spray is carried farther by strong winds.

Reducing salt spray or salt spray damage

Numerous options exist for reducing salt damage including:

Carefully designing planting areas to reduce exposure of trees and shrubs to aerial salt spray. Establish windbreaks to prevent "wind tunnels" that can carry aerial salts farther and at higher wind speeds. Use salt-tolerant shrubs or herbaceous borders (especially denser evergreens) as windbreaks to help intercept aerial salt drift before it reaches sensitive plants.

Grouping tree and shrub species to shield them from wind and drift, with the most tolerant species in higher exposure areas to shield moderately tolerant species.

Maintaining appropriate soil fertility and moisture conditions to reduce additional stresses, and to help combat desiccation.

If feasible, rinse salt spray off trees and shrubs after storms and high winds.

As with saline soils, selecting and planting salt spray tolerant trees and shrubs. Avoid plants, such as azaleas, that are considered especially sensitive to salt spray.

White pines are very sensitive to salt spray and air pollution. Salt spray damage will be a problem after recent storms. Salt spray from the Delaware Bay, carried by strong Northeast winds, will affect trees inland for a number of miles. Eastern white pine will be one of the trees with noticeable salt spray damate. The eastern side of the trees will look “burnt”. Other nearby trees and grass may not be affected. Unfortunately, many of the trees will lose most of the browning needles. The candles or new needles (new growth) are just coming out. Normally pines keep last year’s needles, plus this years and will shed the three year old needles in late fall. White pines will look bare from the extra needle loss, but should live.

Information adapted from a Virginia Tech Factsheet on salt tolerant plants and an article by Derby Walker, Extension Agriculture Agent, Retired, UD.

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