What Makes a Perennial Salt Tolerant?

Effects of Salt

• Aside from proximity to an ocean or deicing salts, saline soil also results from natural weathering of rocks, which releases mineral salts such as calcium, magnesium and sodium. This condition is most prevalent in semi-arid or arid regions where rainfall doesn’t leach salts through the soil, though irrigated landscapes also often experience high levels of saline, especially when deep-rooted indigenous plants are replaced by shallow-rooted perennials and crop plants. High salt levels affect both seeds and mature plants; saline creates drought-like conditions in which plants can’t absorb nutrients and water, thereby stunting initial seed germination and continuing growth. Certain types of salts can even be toxic to plants.

Tolerance

• Perennials’ ability to thrive in salty conditions, or salt tolerance, is defined by plants’ relative growth when saline is present, according to the Government of Alberta. Soil salt levels range from non-saline to very strongly saline and are measured by determining a soil’s electrical conductivity. Higher saline levels have higher conductivity. Soil ratings are used to identify which plant species can tolerate specific saline levels.

Characteristics of Salt-Tolerant Perennials

• Tolerant plants, known as halophytes, are those that thrive in highly saline soil. According to the Society for Experimental Biology, no single trait makes a plant salt tolerant; rather, a complex blend of physiological and genetic traits allow plants to survive in salty sites. Most efforts to create halophytes through breeding have been unsuccessful. However, most salt-tolerant species have the ability to expel sodium through their roots or store it in their shoots in order to limit absorption by foliage and other sensitive parts of the plant. Not surprisingly, plants native to coastal regions tend to tolerate higher salt levels that those indigenous to inland regions.

Tolerant Perennials

• Perennials tend to tolerate salt better than annual plants. Certain perennial species are especially tolerant. Highly salt-tolerant trees include the yaupon holly, wax myrtle, thornless honeylocust, Southern magnolia, sand live oak, Geiger, frangipani, Eastern red cedar, cabbage palm and bottle palm. Very salt-tolerant shrubs include yucca, rosemary, oleander, pittosporum, inkberry and century plant. Salt-tolerant ground covers and vines include weeping lantana, Virginia creeper, sand cordgrass, liriope, lily turf, English ivy and confederate jasmine. Perennial flowers that tolerate salt include yarrow, seaside goldenrod, lavender cotton, day lilies and blanket flowers.