What is Salt Burn in Plants?
Salt burn is a condition that has many causes that may damage or kill plants. But what exactly causes this condition? And is it treatable? Gardening expert Christina Conner explains what exactly salt burn is, how it happens, what symptoms to look for, and how to prevent and treat it.
Contents
Salt burn isn’t just a dark comedy-thriller film starring Barry Keoghan; it’s also a detrimental condition for plants! And that’s nothing to laugh at.
To really get into the science here—the two elements making up salt (sodium and chloride) work in tandem to displace vital nutrients and dehydrate plants. When salt dissolves, the chloride and sodium ions separate. Instead of taking up nutrients like potassium and phosphorus (the P and K of NPK), the plant takes up chloride and sodium, resulting in nutrient deficiencies. Chloride ions then make their way into foliage, causing visible symptoms like leaf burn and dieback.
Before we get into the article, I’d like to make a distinction: there are some gardening myths mentioning the use of epsom salt, also known as magnesium sulfate. To clarify, this product is not actually salt; it’s made up of magnesium, sulfur, and oxygen. While it won’t give your plants salt burn, we still don’t recommend using it in most scenarios.
The condition has many causes, ranging from environmental to man-made. In this article, I’ll explain why and how it happens, the causes, symptoms, prevention tips, and some salt-tolerant species.
The Short Answer
Salt burn is when the absorption of salt disrupts a plant’s ability to take up water. Salt burn or stress has symptoms, including browning or scorched leaves, deformed growth, and premature fall color on evergreens. This condition has many causes, including sea spray, excess fertilizer, softened water, and road salt. This condition impacts just about every plant type, with houseplants being particularly susceptible. The good news is it is treatable most of the time.
If you can’t avoid it or live in a coastal climate, several species of trees, shrubs, grasses, and other perennials and crops are tolerant.
The Long Answer
Diving deeper into this condition, you’ll learn how and why it happens, what symptoms to watch out for, how to prevent and treat it, and some tolerant plants.
Symptoms
Here are some of the symptoms to watch for:
- Yellow leaves
- Premature fall color or leaf drop
- Discolored, small, and reduced foliage
- Crusty white buildup on the soil surface
- Bowned or burned needle tips on conifers
- Marginal leaf burn (browning of the perimeter and tips of leaves)
- Delayed or stunted development of buds, fruits, and flowers
- Damage, distortion, or death of buds, twigs, and stems
- Witches’-broom deformity
- Damage is only in one area (i.e. the side of the plant facing a road where salt is used in winter)
- Reduced overall growth
This plant issue has many symptoms, some of which may mimic nutrient deficiencies. Before jumping for the fertilizer, I recommend carefully considering any cultural conditions: where are your crops? How often are you fertilizing them?
Why Does Salt Burn Happen?
This condition happens because of osmosis. If you’ve put salt on eggplant or tomatoes before cooking or eating, you’ve seen osmosis in action. This mineral draws out water, which improves the flavor and texture of water-rich fruits and veggies.
Salt has the same effect on plant roots. But instead of leading to tasty food, it leads to plant disease or death. This mineral draws water away from plant roots in a process known as exosmosis, and then it makes its way into stems and foliage via transpiration. This leads to nutrient deficiencies, plant cell death, and dehydration.
What Causes Salt Burn in Plants?
Some of the most common causes of this condition include:
Road salt
In cold areas where rock salt is used to de-ice roads in winter, this is a common issue. This mineral gets to plants in two ways: through being sprayed by cars and through runoff from the street.
Excess fertilizer
Chemically speaking, most fertilizers are salts. This type of burn occurs when fertilizer is applied too frequently, in a too-strong concentration, or in dry soils where the fertilizer doesn’t have an opportunity to diffuse. Fertilizer burn is a form of salt burn. Some crops, like wheat and corn, are less sensitive, while vegetables and beans are most susceptible. Houseplants are common victims of fertilizer burn.
Sea spray and flooding
In coastal areas, sea spray and flooding also trouble plants, particularly non-native ornamentals and edibles. Ocean wind may cause leaves to dry up and drop, and sea spray and flooding cause salt to infiltrate the soil.
Softened water
Many houses have water softening systems that turn hard water soft. These systems work by removing calcium and magnesium and exchanging them for sodium. These hard water minerals impact soap suds and leave hard water rings and limescale. While naturally soft water, like rainwater and distilled water, is good for plants, artificially softened water can lead to salt burn and stress. Softened water impacts houseplants the most.
Is It Preventable?
Yes. Depending on the cause, salt burn and damage can be prevented or lessened. Here’s how to prevent each cause:
Road salt
While we can’t always control what our jurisdiction or city government does, there are ways to use less salt for de-icing. For driveways and walkways, you don’t want to create a fall hazard by using none at all, but you can use less. Combine abrasive materials like sand, cinders, or ash with salt to provide more grit, reducing the amount needed. Apply carefully and avoid heaping piles. In spring, deeply water the soil three to four times to leach it of any buildup.
You should aim to keep your plants about 50 feet away from roads that are iced. If that isn’t possible, protect your plants with a physical barrier to prevent salt from reaching them. Avoid shoveling snow from walkways onto your lawn or plants, or use a raised garden bed to protect your soil. Use sodium-free de-icing products, such as those containing calcium chloride, which are a little safer for plants (but not completely).
Excess fertilizer
Less is more when it comes to fertilizer. When in doubt, do a soil test and carefully observe for indicators of nutrient deficiencies. Do research on your plants’ fertilization needs, including frequency and nutrient makeup. Organic and non-organic fertilizers can both cause salt burn, so carefully follow the dilution instructions for your fertilizer of choice.
Because houseplants have a finite amount of soil, they are particularly prone to salt burn. Both fertilizer and softened water may cause this issue, so it’s important to leach your plants every three or four months (more on that below). Plant houseplants in clean pots without crusty white residue that accumulates on the outside of terracotta pots. Don’t allow plants to sit in wet drainage trays.
Sea spray and flooding
Physical barriers, such as plants or manmade structures acting as windbreaks, help protect against ocean winds. If you use plants, try to design them in a tiered fashion, with grasses nearest the sea breeze and larger trees and shrubs closest to the garden.
Adding lots of organic material and mulching the soil helps to ease some salt stress. However, the best way to prevent this condition in coastal areas is to plant native or salt-tolerant species; more on that later.
Softened water
Generally, individual home softening systems only filter the water indoors, while outdoor faucets are typically still hard, which is better for plants. If you’re unsure if you have softened water, pick up a water test kit and check with your landlord or your local water district. Distilled or rainwater is the best water for houseplants.
Is It Treatable?
Yes. It’s generally treatable, but sooner is best. First, stop using fertilizer. The next thing to do is leach your plants, whether they’re in pots or in the ground. Leaching is the process of removing soil salts.
To leach in-ground plantings, use drip tape or another slow-watering method to saturate the soil. By watering slowly, the water has a chance to reach deeper soil layers. Repeat this process for three or four days.
For houseplants or potted plants, water thoroughly and allow water to drain, waiting five minutes in between waterings. As the water evaporates, you may notice a whitish crust on top of the soil. Carefully remove the top inch of soil and replace it with fresh compost.
Gypsum
Another option for landscape plantings is to add gypsum. Use a lawn spreader or scatter gypsum in a ratio of about a half pound for every square foot. The addition of this mineral makes sodium highly leachable.
Leftover calcium binds with soil particles and adds aeration to the ground, which is especially beneficial for clay soil and helps with leaching. After applying gypsum, it’s important to irrigate the area to let the sodium leach out.
A word of caution on gypsum: Use might cause the leaching of other minerals and nutrients, like iron or manganese, which are important for plants. It may negatively impact beneficial mycorrhizal fungi. I recommend only adding gypsum if water-only leaching doesn’t work or your garden has been flooded by seawater.
Salt-Tolerant Species
If you cannot escape salt, it may be time to consider planting some tolerant plants. Here are just a few examples of moderately to highly tolerant species:
| Trees | Shore Pine, Pinus contorta Red Cedar, Juniperus virginiana Northern Red Oak, Quercus rubra |
| Shrubs | Juniper, Juniper spp. Spanish Dagger Yucca, Yucca gloriosa Century Plant, Agave americana Rugosa Rose, Rosa rugosa |
| Grasses | Perennial ryegrass, Lolium perenne Tall fescue, Festuca arundinacea Seaoats, Uniola paniculata Muhly Grass, Muhlenbergia capillaris |
| Edibles and herbs | Cherry tomato, Solanum lycopersicum Asparagus, Asparagus officinalis Thyme, Thymus vulgaris Spanish Lavender, Lavandula stoechas Rosemary, Rosmarinus officinalis |
| Perennials | Seaside Goldenrod, Solidago sempervirens Sea thrift, Armeria maritima Blanket Flower, Gaillardia pulchella Prickly pear, Opuntia stricta |
| Annuals | Trailing Ice Plant, Lampranthus spectabilis Lantana, Lantana camara Coleus, Solenostemon hybrids Blue Daze, Evolvulus glomeratus |
Key Takeaways
In summary, salt burn makes it difficult for plants to uptake water and nutrients. It is often caused by over-fertilization (especially with synthetic fertilizers), runoff from winterized roads, gardening near the sea, or flooding. You can leach salts from the soil with a lot of fresh water. You can also use compost, mulch, raised beds, or small amounts of gypsum to remediate the ground.
