Tuesday, May 13, 2008

Landscape and Turf - Wet Weather and Drainage

Recent heavy rainfall and flooding bring the topic of drainage in the landscape to mind. The following are some thoughts on the subject.

Drainage problems are evident throughout the state with the recent heavy rains. Excess water reduces oxygen levels in the soil (suffocating roots), causes nitrogen losses through leaching and denitrification, and sets up conditions favoring certain diseases. Turf areas with poor drainage may start to turn yellow. Landscape plants with damaged root systems from last year’s drought will be more susceptible to injury from flooding or waterlogging of root systems and may show wilting once the sun comes out.

Plan now to manage drainage problems. Map poorly drained areas, note water paths and runoff sources, and evaluate outlets. Evaluate underlying soil conditions including restrictive layers and compaction. Consider traditional drainage methods such as swales, drainage tiles, or French drains. Consider diverting runoff water away from poorly drained areas into rain gardens, engineered infiltration basins, or bioretention areas. These systems become fixed landscape features that allow runoff water to accumulate and drain slowly, serving as a filter. Consider tools to deal with soil restriction such as subsoilers or deep aerators. Use core aeration or verticutting to increase aeration in turf once soil has dried. Evaluate current plantings in poorly drained areas and consider alternatives that do better in wet soils or soils with variable drainage.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

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