If nearly 19 inches of rain in June by the 27th wasn’t enough, it is once again pouring down rain at my farm. On the 13th, I had received 9 inches in nine hours. Since my farm is along the South Fork of the Crow River, this meant trouble.
Once the water from impervious surfaces of southeast Willmar flows this way, the river starts overflowing its banks. It has never been this bad — at least in the last 51 years. A big portion of my grove is under water. (And my lawn; the crops are toast.) For this reason I went to the University of Minnesota website to see what hope my trees are going to have.
I felt it was important to pass this information along as I’m assuming I’m not the only one with this problem this year. There were 10 pages of information online so I will try and summarize. For those with problems, go to the U of M website and search “How to manage flood damage to trees.”
First bad news: “Trees are more likely to be damaged by flooding during the growing season than by flooding during the dormant season. When flooding occurs during the growing season, especially during warmer weather, one to two weeks of flooding can cause major, long-term damage to sensitive trees and shrubs, even death. Some species can survive as long as three to five months in flooded situations.
Next bad news: “Water covering the soil reduces the supply of oxygen to tree roots as they must have oxygen to survive and grow. Flood water may contain chemicals from urban areas or agricultural fields that may be harmful to trees when absorbed by their roots. As little as 3 inches of sediment can be harmful, so when flood water recedes, this sediment needs to be taken away.
“Flooding can weaken trees, making them more susceptible to damage from insects and diseases. The likelihood of insect and disease damage depends upon the severity of the flood and tree health. A tree in weak condition before a flood can be further stressed by flooding.
“Flood-stressed trees exhibit a range of symptoms that may include leaf chlorosis, reduced leaf size, early fall coloration and leaf drop, crown dieback or large seed crops or no seed crops in years following a flood. Symptoms may progress and ultimately kill a tree over a period of several years or they may lessen as the tree recovers. It is difficult to link a flood to the cause of tree death years later.
“There are too many potential insect pests and tree species to list all possible sources of insect damage, but the following trees are notorious for insect attacks following stressful periods: all pines, oaks, hybrid poplars, birches (especially white birch) and hickories. Insects to watch for include: pine bark beetles, chestnut borers, bronze birch borer and hickory bark beetle.”
This information was taken from an article written by Mel Baughman, retired professor of forest resources in the U of M College of Food, Agricultural and Natural Resource Sciences. If you are concerned about what all this rain is doing to your trees, it’s a good idea to go to his article and read all 10 pages.
Master Gardener Sue Morris has been writing a column since 1991 for Kandiyohi County newspapers. Morris has been certified through the University of Minnesota as a gardening and horticulture expert since 1983. She lives in Kandiyohi County.