How would salt water affect my lawn, garden? What to know | Home/Garden

Saltwater incursion in the municipal water supply sounds scary. But gardeners shouldn’t panic. This has happened before, as recently as 1988. Other parts of the world that are incredibly productive for growing fruit and vegetables have been dealing with saltwater intrusion for centuries. We, and our gardens, will be OK. 

The risk is that the longer there is excess salt in the water supply, the more salt levels will build in the soil over time. Luckily, salt flushes out of soil each time it rains. It is not a long-term issue. And the coming winter is forecast to be cool and wet. 

Salt water is projected to reach Orleans Parish in about a month, on Oct. 28. Go here to see when the salt water is expected to reach your area.

Home landscaping and flowers

For landscaping, the key is to retain soil moisture after it rains with mulch and compost, which, ideally, we are adding to our landscaping in fall anyway. 

Mulching landscape beds with 3-4 inches or more of pine straw, bark, or wood mulch helps to retain soil moisture from natural rainfall, so there’s less need to irrigate. (Avoid using hay or straw — much of this material is treated now with a persistent herbicide harmful to garden plants, and can carry weed seeds into the beds.)

Adding compost before mulching also helps soil retain moisture. It’s a good idea to lay 2-3 inches of good quality, finished compost in a bed when replanting annuals and perennials.

Bedding plants for seasonal color should be going into gardens in the coming weeks. Salt tolerant seasonal bedding plants include snapdragons, petunias, portulaca, dianthus, penstemons, asters, phlox, chrysanthemums, foxglove, vinca, verbena, lantana, salvias, sedum, yarrow, delphinium, pansies, cyclamen, violas, and coreopsis.

Also highly or moderately tolerant of salinitiy are perennial flowers like bird of paradise, most irises, agapanthus, amaryllis, plumbago, bougainvillea, buddleia, bottlebrush, African bush daisy, hydrangeas, jasmine, Indian hawthorn, and firecracker plant. 

Some plants are especially sensitive to salt, including azaleas, camellias, roses, gardenias, croton and boxwoods. Avoid irrigating them with muncipal water when salt levels climb.

If you haven’t already installed a rain barrel, let this be a call to action. Rain barrels are a great way to reduce your water bill and provide plants with untreated, soft water. They can be purchased or built. There are many DIY tutorials on the internet.

Established woody ornamentals should have healthy root systems and be able to survive a few months with intermittent rainfall. Hollies, magnolias, oaks, and photinia are moderately tolerant, but should already be established in the landscape, since summer is not a good time for planting.

Right now, many landscape plants are drought-stressed, but current cooler evening temperatures should help them to recover, even with less water available. Growth is slowing for the season, and that works in our favor.

Most grass is salt tolerant

Of our four common turf grasses, Bermudagrass, St. Augustine, and zoysia are all salt tolerant and come from parts of the world with elevated salinity.

Centipede grass is not as salt tolerant as the other three turfs, but it is less common in the area.

As the cool season approaches, lawns will grow dormant. Most lawns that were not irrigated all summer are severely drought stressed. If you are resodding this fall, choose one of the salt tolerant turfs and follow normal water schedules.

If you overseed your lawn with ryegrass each winter, good news. It’s salt tolerant. Proceed as usual.

Salt can slow seed germination, but luckily ryegrass can be sown in October through December with good results. You can follow local rain forecasts and sow ryegrass ahead of rainfall to ensure quick germination.

Once germinated, ryegrass can handle salty irrigation water fine.

Salt in the veggies?

We have plenty of options when planning our cool season gardens. Vegetables with high salt tolerance include beets, peppers, broccoli, cabbage, kale, spinach, garlic, asparagus, and tomatoes. The most salt sensitive vegetables include beans, onions, cucumbers, radishes, and celery.

Vegetables with moderate salt tolerance include cauliflower, arugula, chard, collards, carrots, some lettuces, peas, potatoes, squashes, and sweet corn.

But higher salt levels (above 1,000 parts per million) can kill some vegetable plants, including beans and cucumbers. This is where having a rain barrel can come in handy!

Many of our favorite herbs should also fare well, even with some salt in the mix. Rosemary, thyme, oregano, Cuban oregano, savory, marjoram, lemongrass, and mint are salt tolerant.

Basil, lemon balm, lemon verbena, and green onions are more sensitive, but will likely still produce to some extent.

Again, adding soil organic matter (compost) and a thick layer of mulch reduces the need to water vegetable and herb gardens. This is a good practice regardless.

What about fruit trees?

Stunting and leaf burn can result if salts build up in young citrus groves. Watering fruit trees at night reduces water evaporation and salt deposition.

Loquat, persimmons, blueberries, figs, Barbados cherry, guava, passionfruit, pineapple, and bananas are all moderately salt tolerant. Avocado, pomegranate, and citrus are salt sensitive. Citrus varies in salt tolerance based on cultivar and rootstock used. Young trees are more sensitive to salt than older, mature trees.

Established, in-ground fruit trees should be watered once per week, deeply, only if needed. Salty flood waters that inundate and stagnate in fruit trees will kill, but a weekly irrigation of slightly salty water will not.

Commercial citrus nursery producers should look into mobile reverse osmosis trailers, which can be rented from water companies such as Suez, Baker Hughes, Nalco, and ChemTreat. State water quality specialists are working to compile information for commercial growers about options.

If you are growing fruit trees in containers as a patio plant or nursery stock, salts may build up within the reduced soil space over time if you water using salty supplies.

Doing a weekly “flush” using rainwater or some other salt-free source will help prevent this build up even if you are watering daily with salty water. Natural rainfall also accomplishes this. Avoid allowing the containers to dry out. It’s better to water frequently and keep the soil hydrated. Watering frequently and applying more water than the plant will use can help to reduce salt stress.

Most fertilizers contain salt, and it is better to fertilize at low rates more frequently than high rates less frequently when plants are exposed to irrigation water containing elevated salt.

Flush house plants and container gardens

House plants and container-grown ornamentals have a very small soil profile to live in. Salts and mineral deposits build up in the soil even under normal conditions.

You may have noticed a white buildup on your pots, or a slight crust on the soil surface of potted plants. If salts are allowed to build up, it can harm the plant.

Flush the pots with fresh water every 4-6 months. Let the water drain through and out of the bottom of the pot. The amount of water used should equal twice the volume of the pot.

Commercial nursery producers and garden centers

Commercial nursery producers and garden centers should look into getting small desalination units for irrigation water. These are available via online retailers.

This pattern of dry, hot summers will increase chances of saltwater intrusion in the coming years, so such units would be a good investment.

Local and state industry groups may want to investigate cost share options to help mitigate the cost of such units. State water quality specialists are currently working to compile information for commercial growers about options.

Keep a record of what crops manage to thrive in spite of the prolonged drought and any salt exposure. Other parts of the world have found locally adapted crops that can handle these conditions, and we can too. Those are the plants you’ll want to use for the coming few years with the projected weather patterns.

Adaptation is key to resiliency. Gardeners are no exception. Tremendous changes have happened in home horticulture in just the past few decades as gardeners have begun to use hardy native plants in their yards, or design spaces to support pollinators and wildlife and work to conserve resources.

Questions?

LSU AgCenter local agents and state horticulture and livestock specialists are working hard to get accurate, research-based information out to home gardeners, green industry professionals, farmers, and growers in a timely manner. Please reach out to your parish agent for clarification or questions, we are here to help! If local agents can’t answer, they can connect you to state specialists or industry leaders.

Plaquemines and St. Bernard Parish: Anna Timmerman, (312) 846-0689 (cell), [email protected].

Orleans Parish: Dr. Joe Willis, (504) 258-3392, [email protected].

Jefferson Parish: Chris Dunaway, (504) 736-6519, [email protected].

St. Charles Parish: Gabriel LoCoco, (985) 785-4473, [email protected].