The southeastern corner of South Dakota, northwestern Iowa and northeastern Nebraska have been inundated with excessive and record rainfall over the last 7-10 days resulting in saturated soils and flooding in many areas. Many other areas have also been experiencing above average rainfall. When it is too wet it is difficult to keep up with regular garden and yard maintenance. The excessively wet soils can also damage some plants or even kill them. When gardens and yards are flooded, even more severe damage can occur such as causing the death of lawns, flowers, shrubs and trees. Excess water forces the oxygen out of the soil which in effect causes the plants’ roots to die or drown from lack of oxygen.
Repeated rainfall can make it difficult to be able to work in the yard to do such things as mowing the lawn or weeding the garden. Weeds and grass can grow like crazy when growing conditions are ideal for them. The unusually cool spring weather we have had with the extra moisture means that a typical Kentucky blue grass lawn will need to be mowed up to twice per week to keep the grass from getting too tall. We recommend that you do not remove more than 1/3 of the height of the grass in a single mowing. But, it is easy to fall behind and end up with very tall grass that will bunch up and leave piles of grass clippings on the lawn. Those extra clippings should be raked up or the lawn should be mowed with a bagger to catch the clippings so that they do not pile up and yellow the grass or look unsightly. Removing too much leaf material can also stress the grass and make it look yellow.
Wet soils are more easily compacted than dry soils so mowing or even walking over wet soil can cause significant compaction problems which can lead to other problems like poor grass growth, bumpy lawn from old wheel tracks or promote the growth of weeds that can tolerate compacted soils better than typical lawn grasses. Try to avoid walking or operating equipment on wet soils, wait until it dries out.
Excessive rainfall can leach nitrogen from the soil, particularly if areas of a lawn are flooded or have water standing for several days, causing the grass to turn yellow. However, flooding can also kill grass roots, decreasing the ability of grass and other plants to take up any kind of nutrients, leading to further nutrient deficiency symptoms. Loss of roots can lead to wilting of plants or marginal burning of leaves when the weather heats up, later in the summer. Watering is the natural response to seeing a wilted plant, however, if the plant is wilted because many of its roots have died, overwatering at this point can easily kill the plant. Do not water until the soil begins to dry out again.
If you have seen yellowing of turf or other plants try making an application of lawn fertilizer at half the regular rate to help replace the missing nitrogen but not stimulate excessive growth. Garden plants can be side-dressed with fertilizer too, but be careful you do not use too much. Consider using a complete fertilizer like 10-10-10 at a rate of about 1-2 TBS per plant, sprinkled in an area 6-8” around each plant. Organic fertilizers can be used too and are less likely to burn tender roots that may be recovering from excess water damage. You can use a water soluble fertilizer and water the plants to give them a nutrient boost too, following the mixing instructions on the container.
Hail damage has been another common occurrence in many of the thunderstorms that have occurred in recent weeks. Damage can be minor to severe. In many cases herbaceous plants suffer mechanical damage, primarily to the leaves and stems. If the damage is not too extensive, plants will recover and produce new leaves and flowers later in the summer. If damage is severe, plants may not regrow this year but produce new growth next spring. All the gardener can really do is remove damaged portions of the plant and allow the plant to recover as best it can on its own after that.
For additional information see the iGrow article Flooded Lawns And Gardens.