Will My Trees Survive Saltwater Flooding?

Hurricane Helene pushed storm surge into coastal Pinellas in September 2024. UF/IFAS Pinellas County Extension reported a confirmed surge of 7 feet above the average high tide, not counting waves. Hurricane Milton followed that October.

Seawater carries about 35,000 parts per million of dissolved salt. The Pinellas Extension office notes that seawater is strong enough to dry out almost any native or introduced tree or shrub within 48 to 72 hours. That is why leaves can brown so fast after a surge.

Brown leaves are not the same as a dead tree. That is the reason the waiting section below matters.

Salt works against a tree in two ways. In the soil, it pulls water out of the roots instead of letting the roots draw water in, so the tree acts thirsty even when the ground is wet. On the leaves, salt dries out the tissue directly.

Salt spray and salt flooding are different stresses. Wind driven spray lands on the twigs and leaves, often on the side facing the water. Flooding puts salt in the root zone. UF/IFAS Sarasota Extension gives a good example: dune sunflower can handle sea spray but cannot tolerate being under salt water.

• Scorched leaf edges, worst on the youngest leaves, on trees that are not salt tolerant.
• Leaves yellowing, browning, or dropping.
• Burned or stripped foliage on the side of the tree that faced the water.
• Drooping leaves, and dieback of twigs and limbs.

UF/IFAS Monroe County Extension notes that damage from salt water can take a couple of weeks to show. Some trees look fine at first and decline later. Others look rough for months and still push new leaves.

UF/IFAS rates trees and palms for how well they handle salt. From the UF/IFAS salt tolerant plant list and its tree fact sheets, here is where some common Pinellas trees land:

• Salt tolerant: live oak, cabbage (sabal) palm, Washingtonia palm, coconut palm, sea grape, and yaupon holly.
• Moderately tolerant: queen palm, Canary Island date palm, dahoon holly, and bald cypress, which is rated moderate for salt spray.
• Low tolerance: red maple, rated poor for salt in the soil and low for salt spray; laurel oak, rated low for salt spray; crape myrtle and American holly, rated only slightly tolerant.

Two cautions. Many of these ratings are for salt spray, and standing in salt water is harder on any tree. After Milton, UF/IFAS Sarasota Extension reported live oaks, normally resilient, showing severe salt and drought damage. A tolerant rating means a better chance, not a promise.

1. Fresh water, and plenty of it. UF/IFAS Extension agents agree on this one: move the salt down and out of the root zone with fresh water. The Pinellas Extension office calls rainfall the ideal flush. If rain is short, water the root zone out to the dripline, the outer edge of the canopy, and rinse the leaves once the salt water is gone.
2. Check your irrigation source. If you water from a pond, canal, or shallow well the surge reached, that water may be salty too. UF/IFAS advises testing it before you use it.
3. Hold the fertilizer. Fertilizer adds more salts to the soil. UF/IFAS Extension agents in Pinellas and Sarasota both advise against fertilizing flooded plants.
4. Go easy on pruning. Cutting off green leaves adds stress. Take out what is clearly broken and leave the rest until the tree shows you what is alive.
5. Test the soil. After Helene, Pinellas County Extension offered soil chloride testing for a small fee. Call them for current details.

Soil testing is also where our plant health care work starts, so that is where I would begin on a flooded property.

You will see gypsum recommended a lot after a surge. UF/IFAS guidance, written for lawns and sports turf, explains that gypsum swaps calcium for sodium in the soil and helps where sodium has damaged the soil structure.

The same guidance says sandy soils, like most of what we have in Pinellas, may not need it, and that gypsum only does its job if enough fresh water follows to carry the salt down. It also suggests a simple test to see whether your soil has a sodium problem before you buy any.

In my opinion, gypsum is not a substitute for flushing. If a soil test shows a sodium problem, it may be worth adding. If not, fresh water is doing the work.

UF/IFAS Extension agents in Monroe and Pinellas counties both advise watching for new growth before pruning or cutting back flooded plants. I apply the same patience to removal decisions on salt damaged trees.

In my opinion, a tree that pushes new leaves the following spring is showing you its roots still work. A tree that stays bare through the next growing season is a different conversation. Our page on when tree removal is necessary covers how we weigh that.

The exception is safety. A tree that is cracked, uprooted, or leaning toward the house is a safety question, not a salt question. Our storm response page covers that work.

When you do replant, the Pinellas Extension office suggests waiting until weeds and other plants start sprouting on their own, a sign the salt has moved down. Pick salt tolerant species for the spots the surge reached.