Are your trees drowning? OK, we know they probably aren't as flooded as the trees in this picture, but our point still stands! As heavy snow melts into spring, you'll likely find your trees sitting in soil saturated with water. Too much water sitting at the base of a tree can cause a myriad of problems; it's almost as bad for trees as too little water!
A traditional life preserver might not be the answer for these leafy giants, but a little knowledge – and knowing where to seek assistance – can help trees survive spring thaw. While some trees are suited to survive occasional floods, most are not. In addition, as a tree becomes older, its ability to adapt to abrupt environmental changes decreases.
“Trees must maintain a proper water balance,” says Tchukki Andersen, BCMA, CTSP* and staff arborist with TCIA. “Although most trees can withstand moisture conditions from very dry to very wet for short periods of time, continued extremes can cause serious problems, depending on the tree species,” Andersen explains.
Some species – such as some oaks, pines and junipers – have adapted to survive drier conditions. Trees that grow along rivers (such as willows, poplars, cottonwoods and sycamores) and trees that grow in or around swamps and ponds (such as red maples, gums and pond cypress) can also grow in wet conditions.
Unfortunately, most tree species are not equipped to deal with these conditions, and are thus susceptible to a malady known as "flood injury." Flood injury occurs when soil becomes saturated with water; there doesn’t need to be an actual flood to cause flood injury. This can make identifying the symptoms a bit tricky, so keep reading to learn more about the warning signs.
How to look for flood injury
Flood injury is usually expressed through changes in the foliage. One symptom in particular, chlorosis, is commonly caused by flood injuries. Chlorosis is the yellowing of leaves caused by a decrease in the amount of chlorophyll (green pigment) in the leaves. This symptom can look like a symptom of a disease, but is often caused by non-disease problems, such as excessive water. A professional arborist can determine if chlorosis is caused by a pest (which can be controlled), or by water damage.
When flood conditions are prolonged, another symptoms known as root dieback manifests. During root dieback, soil is so saturated that there is not enough oxygen available to the tree roots. Without the proper balance of oxygen and carbon dioxide, roots can’t survive. Eventually the tree is not able to absorb adequate moisture, despite the flood condition. The tree will exhibit symptoms similar to leaf scorch, where a tree’s leaves turn brown and die due to a lack of moisture in the leaves.
Symptoms of flood injury, in the order that they develop on the foliage, are:
• Slight wilting or drooping of the foliage
• Yellowing and browning (necrosis) of leaf edges
• Browning in the center of the leaf
The symptoms usually start at the top of the tree or on the ends of branches, and spread throughout the entire crown. The symptoms are often more severe on the side of the tree facing the prevailing winds.
Hire a professional
The best prevention for this problem is to avoid planting flood-intolerant trees in areas that are frequently flooded, or to select a wetland tree/shrub for planting instead. Ensuring that proper drainage is avaialble in another way to mitigate flood injury risk, but this is typically to only practical short-term solution.
If you think your trees might be at risk for serious flood damage - espeically if they display the symptoms mentioned above - your best bet is to hire a professional arborist to take a look at your trees. A trained arborist will know precisely what symptoms to look for, what sort of drainage is appropriate for your trees and the surrounding landscape, and will be able to provide you with practical solutions.
To find a tree care company in your ZIP code, click here and start searching the TCIA member database. Our member companies, many of whom boast industry accreditation and other certifications, are well-equipped to evaluate your canopy and make the appropriate recommendations.