Post-Storm Flooding and Your Landscape

Wow, have we seen a lot of rain thanks to Tropical Storm Debby! Many parts of Pinellas County are completely saturated and some are still dealing with standing water. Many plants in the landscape are not tolerant of standing water. Under these conditions the roots are unable to get oxygen and essentially the root system suffocates. Some plants can tolerate up to a week or so in these flooded conditions while others will be damaged after only a day or two. Recovery from this situation is just as varied, as some plants will recover in just one growing season while others may decline and die. Healthy established plants will generally fare better than older stressed plants and young seedlings. Here are some of the symptoms that you might see above-ground if your plants have root damage from standing water:
-leaf yellowing or browning
-droopy foliage
-leaf drop
-leaf and stem wilting
-stem and limb die-back
-plant death

There are some things you can do after this occurs to lessen the damage to some plants. If you have container plants that have been flooded put them up on blocks, bricks, gravel, etc. to allow the drainage of excess water. Due to erosion you may have sediment, mulch, etc. deposited on your plants after the water recedes. Carefully remove this sediment so as not to harm the roots. You may also have exposed tree roots where the soil was washed away. These roots should be covered with soil to protect them. Try to return the soil to its original depth/condition, as putting too much soil on the roots will also reduce the oxygen available to them. The goal is to return to pre-flood conditions as soon as possible. Furthermore, according to the University of Florida, “trees showing signs of flooding stress should have up to ½ the leafy tree canopy removed to reduce the stress imposed by soil conditions. Reducing the size of the canopy will improve the chances for tree survival”. It is recommended that you consult an arborist for this activity.

Wet soils are also favorable for a number of soil-borne root and crown rots including Fusarium spp. and Phytophthora spp. These organisms are responsible for a number of root and crown rots that are potentially fatal. Keep a watchful eye on your landscape after flooding for symptoms that often look similar to drought stress like wilting or a dull appearance to leaves. Contact Extension if you suspect these infections as there are different control and sanitation methods that may help manage the spread of the organisms. Different plant species and root and crown rot species call for different responses that would be too numerous to explore here. So, keep an eye on your landscape and an umbrella at the ready.

Finally, this post mainly addresses freshwater flood impacts.  If you have experienced salt or brackish water flooding you will want to flush the plants root zone and rinse the plant with fresh water once the salt water recedes.  Carefully wash away sediment and debris as well.  After a thorough rinsing and flushing use the above methods to promote drainage and aeration as much as possible. 

Good luck- and consider this a warning from Mother Nature.  Be sure to have a hurricane plan in place for your family, pets, property, and landscape!