What Makes Plants Salt Tolerant?

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Switchgrass (Panicum virgatum) is a salt tolerant native grass.

Wintery roads and sidewalks are often coated in salt for most of the winter. As snow melts, this creates a saline brine that infiltrates the garden beds and soils abutting the access ways. Some plants find this most unpleasant and eventually succumb to the salt. Other plants do not seem to mind these conditions at all.

Of course we have many salt tolerant options, so whether you are planning a landscape near the shore or near a sidewalk we have plants for you. Simply use our plant characteristics search for salt tolerance and you will find a list of plants that will work.

You can find many lists of salt tolerant plants online but what makes a plant salt tolerant? Why do some do just fine through the winter and why do others just not put up with salt at all? How can you mitigate the damage winter salting may cause your plants?

The photos intertwined below are of just some of the salt-tolerant plants we carry at New Moon Nursery.

Salts in Plants

First it is important to remember that soils are full of salts even when the weather is sunny and dry. Many of the nutrients essential to plant growth are salts. Normally, these are flushed through the soil at regular intervals through irrigation and weather and so tend not to build up in the soil. Occasionally, as in the case of wintery weather, salts may build up in the soil.  Also, as happened in the case of NJ and NY during Hurricane Sandy, seaside and inland gardens may experience salt exposure due to winds blowing salt water and salt spray far inland.  This addition of salty water actually draws the water in the plant to outside the plant. This results in a plant that is basically dying from drought stress even though it is growing in soils filled with water. This is because water with low concentrations of salt (that found in the plant) will move to areas of concentrations of higher salts because there is less water (remember osmosis from biology class?). So the excess salts in the soil are drawing the water out of plants. This is why plants suffer when there are salts in the soil or the irrigation water. (Learn more! Visit this page for an excellent, easily understood explanation regarding salt damage in plants.) The basic gist is that as salt levels increase in soils, many plants find it more difficult to take up water.

There are many types of salts used in a variety of ways around the landscape throughout the seasons. Sodium chloride – Rock Salt – is the most damaging to plant materials. Potassium chloride is used primarily as a fertilizer and occasionally as a deicer. Because it is a fertilizer, this is safer to use around plants. Magnesium chloride is most commonly used by municipalities and maintenance companies, it is relatively safe for plants in moderate amounts and has low corrosion and pollution potential. All of these have chloride in common and that is the component most harmful to plants. (Now beet juice is being added to salt brines.)

Research is under way at the University of Illinois and other institutions to determine what plant gene makes it possible for some plants to tolerate salts but as of now scientists are still unclear why some plants seem to tolerate salts better than others. This research is geared towards developing food plants that will grow better in the high salinity arid regions around the world and those that may develop as our climate changes, but this research will certainly shed some light on the mysteries of salt tolerance in our landscape plants as well.

Some Plants Love Salt

 

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Mangroves are halophytes

Halophytes, or salt-loving plants do exist. These are the plants that thrive in high salinity situations, like along coastal salt marshes, salty lakes, along bodies of saltwater. Very few of the world’s plants feature this characteristic – which is interesting considering how much of our planet is covered by salt water. Some examples are Mangroves, Spartina (Smooth cordgrass) and Panicum virgatum (Switchgrass)Plants that fall in this category deal with salt in a few ways – excluding, sequestering or exuding. Some plants have leaves that sequester the salt in special structures which then rupture and release salt back into the environment. Other plants have specialized structures that have evolved to collect the salts which are then forced through pores before they reach the vascular system of the plant. Still other plants collect the salts and store them in plant cells that are less susceptible to salts than others in the plant.

Some Plants Do Not Love Salt

Plants that do not tolerate high salt content in soils are called glycophytes.  These plants prefer soils low in salts. Most of the plants we landscape with fall into this category. But that does not mean they will not tolerate salt and some are better at dealing with salt than others.

Prevent Soil Salt Buildup

You can better ensure all of your plants will do well through the winter if you work to prevent salt build up in your soils in the first place. Protection from salt buildup can be achieved in a few ways. First consider the diversity of your landscape. Deep rooted trees and shrubs keep the water table deeper in the soil, keeping the salts down there too. Replacing a diverse landscape of deep rooted plants with shallow rooted plants eventually brings the water table up, and bringing the salts along with it.

Avoid excessive irrigation and fertilization. Regular irrigation over time can cause salt build up. Most fertilizers are made up of salts. Applying more fertilizers than the weather or irrigation can move will result in a build up of salts and damage to plants.

Improve drainage. Allowing water and salts to drain further will prevent the build up of salts. Aerate the soils next to regularly salted areas and increase organic matter content of the soils to enhance drainage. You can also be sure to modify drainage so that meltwater drains away from desirable plantings.

Flush your soils in early spring. If you have had a lot of salt application over the winter with little precipitation to wash it away consider leaching the salts from your soil by applying fresh water early in the spring.

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Swamp Mallow is a salt tolerant summer stunner.

The adaptability of plants to the conditions we cause are endlessly fascinating. Seems like no matter the condition, there is a plant that will grow there and, hopefully, we have that for you.

 

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