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 It is important to understand what is happening to plants
growing in these conditions, and what to expect later. It is a
wait-and-see situation. Many herbaceous plants are experiencing
injury symptoms now. Visible injury symptoms on trees and shrubs
may not occur for a year or more. Following is a discussion
about flooded and water soaked plants, based on an article done
by Rhonda Ferree several years ago.
Injury symptoms, which vary according to several factors,
include decreased growth of shoots and roots, decreased
transpiration rate, yellowing leaves, twisting of leaves, leaf
drop, death of roots, increased susceptibility to attack by
predators and pathogens, absence of fruiting, and death.
The main reason injury occurs is related to oxygen availability
in the soil. In flooded or waterlogged soils, oxygen diffuses
slowly and reduces in concentration to a few percent or zero. As
oxygen is excluded from roots, there is decreased aerobic root
respiration, root growth, transpiration, and translocation.
Although survival is directly related to species’ tolerance of
waterlogged soils, other factors are important—including the
soil type; the time, duration, and depth of the water; the state
of the floodwater; and the age and size of woody plants.
Tolerant species, such as bald cypress, little leaf linden, red
twig dogwood, mulberry, silver maple, and willow, can live on
sites in which the soil is saturated for indefinite periods
during the growing season.
Moderately tolerant species, such as green ash, hawthorns, honey
locust, pin oak, red maple, river birch, sweetgum, and sycamore,
can stand saturated soil for a few weeks to several months
during the growing season, but these species die if waterlogging
persists or reoccurs for several consecutive years.
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Weakly tolerant species, such as American holly, balsam fir,
black walnut, burr oak, catalpa, hackberry, Douglas fir, eastern
cottonwood, and red oak, can stand relatively short periods of
soil saturation—a few days to a few weeks—during the growing
season, but they die if waterlogging persists for longer
periods.
Intolerant species, such as American beech, black locust,
crabapples, eastern hemlock, flowering dogwood, paper birch,
pines, redbud, spruces, sugar maple, tuliptree, white oak, and
yews, die if they are subjected to short periods of 1 or 2 weeks
of soil saturation during the growing season. White pines and
burning bushes are among the most sensitive, with saturation for
as little as two days can cause root death, followed by plant
death.
Unfortunately, little can be done to prevent damage to plants
growing in waterlogged soils. If a woody plant shows injury
symptoms, such as leaf drop, do not immediately replace it. Some
plants will show initial injury symptoms and then recover. Many
woody and herbaceous plants, including turf areas, will not
recover. Be patient. Whether your plants are simply waterlogged
or actually growing in flood areas, it will take a while to see
the full extent of plant damage.
[By JOHN FULTON, COUNTY EXTENSION
DIRECTOR SERVING LOGAN, MENARD, AND SANGAMON COUNTIES]
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