Fortunately, Hurricane Debby blew through South Carolina, but she left behind standing water, damaged trees, and other landscape issues. After the storm, homeowners can be left with a real mess to clean up in their yards. The Clemson Home and Garden Information Center (HGIC) has compiled some answers to the most commonly asked questions we receive regarding saltwater intrusion and storm damage to landscapes affected.
Hurricane Debby blew through South Carolina this week, leaving behind standing water, damaged trees, and other landscaping issues.
Zack Snipes, ©2024, Clemson Extension
My yard, including my irrigation well, was recently flooded with salt water! Is there a solution?
The good news is that excess sodium can be flushed from the soil over time. Factors such as the soil type and how well it drains will affect how long it will take to reduce the salt concentration. Rain or irrigation water helps by diluting and leaching salt from well-drained soils, and it can take a few months to a year. Poorly drained, mucky soil may take years to recover.
Additionally, high water tables inundated with salt water from the storm can impact shallow irrigation wells, making them unsuitable for watering plants or flushing soil.
If your irrigation source is suitable, approximately six inches of irrigation will flush 50 to 70% of the sodium from the soil, but only apply one inch of water at a time.
The Clemson Agricultural Service Lab offers irrigation water testing to help determine if salinity is an issue in an irrigation water source, such as a well or pond. This service is not intended to assess water quality for drinking purposes. There are several irrigation test options, but for storm-affected areas, we recommend the “Special2” because it includes pH, salinity, major and minor elements that plants require, plus bicarbonate, carbonate, and the sodium adsorption ratio. Your county horticulture or water resources Clemson Extension agent will be able to help interpret the results from this test.
The unfortunate news is that even short periods of flooding can cause damage to many plants, including trees, shrubs and turfgrass. Read on for more information about flooded landscapes. For more information on Irrigation Water Testing, see SC Regulatory Services Irrigation Water Analysis.
Should I get my soil tested after a storm? How often and when?
Clemson Extension recommends regular soil testing as a best practice for fertility management. If you have had your soil tested previously using the “Standard Soil Test1” a follow-up soil test after the storm may help determine how much, if any, excess sodium remains in your soil. This can be done after the soil dries out a bit; it is not something that must be done immediately.
If you live in an area where saltwater inundates your yard often, the Clemson Extension Agricultural Services Laboratory offers a soluble salt test, “Soluble Salt⁴”, for an additional $3. A sample taken now and again in six months to a year, the results can help gardeners gauge if soil salinity has changed. Please note that the “Soluble Salt4” test is only for mineral soils, not soilless media used to fill raised beds or containers. For more information on how to collect a soil sample, see HGIC 1652, Soil Testing.
If you need to know the location of your local county extension office, please visit the website link below, where you can find the closest office to you.
Clemson Cooperative Extension County Offices
Will gypsum or sulfur applications help remove salt from the soil?
On well-drained soils, 1 to 2 tons of gypsum per acre or 25 to 50 pounds per 1000 square feet can help reduce sodium levels in the soil. However, if your soil doesn’t drain very well, the root desiccation problem could be intensified by applying gypsum.
Granular sulfur may also help remove salt from soils naturally high in calcium. The recommended rate of sulfur is no more than one application of 10 pounds per 1,000 square feet per season. However, caution should be used when applying sulfur, as the temperature must be around 75 degrees F to avoid damaging plants.
How does this work? The smallest particles of soil in your yard are negatively charged colloids that can chemically attract and hold on to positively charged ions, such as the nutrients found in fertilizers and, in this case, sodium (Na+) from salt water. Each soil particle only has so much room for these positively charged ions to cling to. When gypsum, also known as calcium sulfate, a positively charged ion, is applied and watered into the soil, the calcium in the gypsum effectively knocks the sodium ion off the particle, leaving it free to wash away in the water.
Will my plants survive after a flood?
The best answer we can give is “maybe.” Saltwater inundation can be more detrimental to some landscape plants than freshwater flooding. In addition to starving for oxygen, roots in saltwater-filled soils are dried out by the osmotic pressure. The salt pulls water from plant roots, inhibiting water uptake and causing desiccation and plant death. The good news is that many plants that are native to our coastal region are perfectly suited to withstand saltwater intrusion much better than plants that may be native to other ecosystems. For a list of plants that can tolerate salt along the coast, see HGIC 1730, Salt Tolerant Plants for the South Carolina Coast.
Keep in mind that you may need to reconsider your landscape’s plant selection and even redesign it completely after a storm. Shady areas may now be in full sun if a major tree was lost.
Fortunately, leaves stripped off branches due to high winds will re-sprout, but it may take a couple of seasons to regrow branches and limbs. Stressed plants will be more susceptible to pathogens and insect pest problems. Use good pruning techniques to remove crossing, damaged, or diseased branches.
Fertilize appropriately the following spring or summer, and water weekly during the growing season. The recommendation for established trees and shrubs is 1 inch per week. Over-watering can be problematic, and fertilizing in the fall and winter is not recommended.
While not native, some turfgrass species are more tolerant of salt than others. St. Augustinegrass exhibits the best salt tolerance, followed by Bermuda and Zoysia. Centipedegrass does not fare well when flooded by saltwater.
St. Augustinegrass has the best salt tolerance.
Zack Snipes ©2024, Clemson Extension
For more information on saltwater intrusion remediation on turfgrass, see HGIC 1224, Saltwater Intrusion Remediation on Turfgrass.
Can my trees be saved?
Storms can cause drastic damage to branches, limbs, or entire trees. Trees that have survived prevailing winds for many years may fail in a storm if the winds come from the opposite direction. This problem is compounded if the tree is in full leaf, overgrown, or has root rot issues. After a tropical storm or hurricane, trees and shrubs may have broken branches, defoliation, completely or partially exposed roots, and/or leaning trunks with the ground bulging on one side.
After a storm’s wind and rain have injured trees and shrubs, assess the damage after it’s safe to do so. Seek professional help if the job warrants an arborist. Use this link to find a certified arborist in your area: Trees Are Good: Find An Arborist
Clemson Extension recommends arborists with an International Society of Arboriculture (ISA) certification. Use the ISA website to find or verify the credentials of an arborist near you. We recommend an arborist that offers diagnostic and consulting services.
If the damage is minimal, keep plants watered, prune damaged branches, and keep an eye out for signs of insect or disease problems. Landscape plantings should be reevaluated for altered light and wind patterns. Use mulch around new and established trees and shrubs, but don’t apply more than a few inches deep or up against the bark on the trunk. For more information on properly mulching an area, see HGIC 1604, Mulch.
How do you prune shrubs and trees before a storm hits?
Proper pruning of your trees and shrubs at the correct time will help prevent future storm damage. For more information on proper pruning practices, see HGIC 1003, Principles & Practices for Pruning Trees and HGIC 1053, Pruning Shrubs.
