Excessive moisture displaces oxygen in the soil and plant roots can suffocate as a result.
Many plants are intolerant of having their roots submerged for extended periods of time.
Even though standing water may not be present, poor drainage is often responsible for reduced growth and survival of plants in our landscapes. When landscaping sites with poor drainage, it is advisable to start with plants that are tolerant of those conditions. Plants native to wet bottomland areas often thrive under these conditions. When selecting and planting trees and shrubs for poorly drained sites, it is important to recognize that plants often need to acclimate to these conditions before they are able to tolerate flooding and low aeration. Even plants that are very tolerant of poor drainage will have shallower root systems on poorly drained sites.