University of Maryland Extension

Excessive Water and Changes in Water Flow

overwatered evergreen

Key Points

  • Too much moisture can be just as damaging as too little. Many plants cannot tolerate 'wet feet'. Excess moisture can result if soil is poorly drained, naturally wet, or over watered.
  • Climate change is impacting the frequency and types of rain events we are experiencing in Maryland. Data shows that much more rain is falling as downpours now than in the past.
  • Changes in the natural flow of rainwater can have an adverse effect on plants. Sometimes, the correction of drainage problems elsewhere on a site diverts water to a tree or shrub, adding more water than it can handle.
  • Another common problem is a downspout that does not drain away from the house.  The resulting puddling in the garden damages plants

Problems caused by excess water

  • Excess soil moisture can reduce oxygen in the soil, damage fine root hairs, and render the root system unable to absorb water.

  • Plants exposed to excess moisture show the same symptoms as plants under drought stress. The primary symptom of excess moisture is yellowing of lower and inner needles. 

  • If excess water continues, plants may wilt, followed by scorch, needle drop, dieback, or death. 

Management 

  • Select plants that tolerate soil and moisture conditions at a specific site.

  • Group plants together with similar water requirements.

  • Properly water trees and shrubs, taking care not to drown your plants.

  • Take the time to observe the flow of water after a rain or irrigation. Look for leaking gutters and downspouts that do not empty far enough away from the building. Correcting a problem can be as simple as removing a little soil or mulch away from one spot to let the water flow away naturally. In some cases, a total regrading of the site may be necessary.

  • Identify areas that stay wet to determine the causes and possible solutions. 
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