Rain extreme

Horticulture Hints

In recent weeks, many regions of Iowa have been deluged with an excess amount of rainfall this year. Most gardens only need an inch or two of water per week and too much rain can have a negative impact on your yard and garden plants.

Over-watered, saturated soils result in a condition called waterlogging, when the soil is filled to capacity with water. Waterlogging deprives plants of oxygen. Plants need oxygen for cell division, growth and to uptake and transport nutrients. Plants in poorly drained areas are especially prone to waterlogging.

Yellowing of plants due to lack of nitrogen is a common symptom of waterlogging. Nitrogen, which promotes green, healthy foliage, can be lost from the soil through leaching, as excess rainfall or watering can cause loss of water-soluble minerals in soil. When a plant’s root system cannot access nitrogen in the soil, due to excess moisture and lack of oxygen, yellowing of leaves soon follows.

Wet soil is easily compacted and further restricts soil aeration and plant root growth. Remember not to work wet soil and avoid unnecessary foot traffic in the garden to avoid soil compaction.

Too much rain also increases relative humidity and the risk of disease development in the garden. Proper spacing of plants to provide air circulation is a preventative measure.

Maintaining a well-drained soil helps to prevent waterlogging of garden plants. Addition of compost to poorly drained soils will add organic matter and help improve drainage. Use of raised beds is another idea for those areas of the garden prone to waterlogging.

Did you know? Perhaps this is the year to consider starting a rain garden. A rain garden is a depression in the landscape that collects rainwater from downspouts, across driveways, etc. and planted with native plants that tolerate wet soil. Water collected by rain gardens is absorbed by plants and filtered to surrounding soil within a day, so no mosquito worries, which can occur in a bog or pond garden.

Horticulture Questions? Contact McCormick at yvonne@iastate.edu for information or advice.