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The Homeowners Column
State Master Gardener Coordinator
Wet feet. The cherished sensation of water lapping over our toes as we stroll along a sun-saturated beach or wade in a dog-cooling stream on a sizzling August day. However wet feet in winter translate into glacially soggy shoes and cranky kinsman. We can remove our boots and dry out our "pruney" feet, but plants must hang around and hope for drier days. Horticulturalists refer to plant roots in water-logged soils as a plant with "wet feet".
So what is all this water doing to our biggest plant investment - trees and shrubs? Many variables go into figuring how well a plant will survive water-logged soils or "wet feet". A major variable is plant species. Floodplain trees of sycamore and silver maple tolerate and even thrive in wet soils; whereas, trees and shrubs native to the high side of a slope may quickly suffer in soggy soils.
Woody plants that tolerate waterlogged soils include black alder, green ash, hackberry, bald cypress, redtwig dogwood, eastern larch, red maple, eastern cottonwood, swamp white oak and black tupelo.
Intermediate tolerance includes eastern arborvitae, arrowwood and American cranberry bush viburnum, white ash, basswood, Japanese barberry, river birch, black walnut, gingko, shagbark hickory, sweet gum, tuliptree and bur and pin oak.
Tree and shrubs intolerant of wet conditions include American beech; gray, paper and European white birch; eastern red cedar; cherry; crabapple; flowering dogwood; forsythia; redbud; American holly; saucer magnolia; northern red and white oak; peach; red and eastern white pine; sugar maple; blue, Norway and white spruce; serviceberry and yew. Most of our evergreens suffer under "wet feet" conditions.
So why do plants choke or even die in water-logged soils? Back in grade school you probably learned that plants need carbon dioxide from the air in order to make their food (carbohydrates) through photosynthesis. You may not remember (but it's somewhere in the dusty folds of your brain) plant cells, as well as all living cells including ours, need oxygen in order to respire to use the stored food (carbohydrates) for energy. Plant root cells get oxygen from the air in the spaces between soil particles. When soils are water-logged all the air is pushed out by all the water. Cells basically drown and roots die.
In addition to species, survivability also depends on the plant age, size and general health. More established middle-aged trees tolerate flooding better than young or newly transplanted trees of the same species. Not surprisingly healthier trees are better able to survive flooding.
The type of soil in the planting area also makes a big difference in how well plants survive. Clay soils dry slower than sandy soils.
The characteristics of the flooding event also have an effect. For example: how long the area is flooded (less is best), depth of the water (again less is best) and whether the water is flowing or stagnant. Flowing water and cold water is generally less harmful than stagnant, warm water.
The good news with winter flooding is dormant trees typically tolerate flooding better than actively growing plants. However, it does leave us with a "wait-and-see" situation to determine how much damage has occurred. Damage may even show up years later. Plants stressed by too much water are more susceptible to insect and disease attack.
As water recedes and plants come out of dormancy in spring the dead roots lead to an inability to take up enough nutrients and water for the plants to survive. Trees and shrubs may leaf out fine in spring but twigs and branches quickly die or plants may not leaf out at all. Dead roots may also become infected with root rot pathogens. Tree trunks may rot at ground level.
As we wait for areas to dry, take pictures of your yard now. It may help in diagnosing plant problems next year.