Wet Soils

Most plants don’t grow well in wet and waterlogged soils, which lack enough air for most root systems. Fortunately, some plants have evolved over the years to cope with conditions presented by soggy soils.

Wet soils result from a number of natural and man-made conditions. An area may have a high water table or natural springs, with resident water so near the soil surface that the ground is always wet and perhaps even boggy. Other causes may be hardpan or thin soil, blocked or broken storm sewers, and leaking ponds.

In neighborhoods where new construction is underway, wet soils may be caused by changing grades and adding structures that create new runoff paths for rain. Even gentle slopes allow water to course through areas between buildings like raging rivers, and settle in low swales, where soils soon become waterlogged and water stands on the surface.

If wet soils occur only once in a while and then only after unusually heavy rains, the condition probably isn’t serious. But if the soil in an area remains wet for days after a rain, a solution may be desired or even necessary. Some alternatives for wet soils are fairly simple and inexpensive; others may require engineering skills and a fairly large budget.

A simple system of trenching or French drains is within the skill limits of most home gardeners, and can improve the drainage of a small garden bed.

Raised beds are a simple alternative that allows the usual assortment of ornamental plants to literally rise above the problem.

Lawns with low areas that become soggy at the first hint of rain often can be drained by digging a network of holes through the turf. This can be done with a hand or power aerator. If the problem is surface compaction due to foot traffic, aeration should solve it. If the problem is due to heavy soil that only slowly absorbs water, the aeration will help a little, but perhaps not enough.

A novel solution to this situation was developed at UC Davis. Dig a parallel series of narrow trenches a foot or more deep in the wet area with a chain saw (using a chain you don’t mind ruining), then fill the trenches with coarse sand. The sand will keep the trenches open and allow water to run into them. Grass will soon cover the trenches, hiding them. The effect is to increase the surface area of the lawn in the wet spot so it absorbs water faster.

One obvious yet often overlooked solution to wet soils is to create a water garden or bog garden in the damp area. Another good solution is to select plants that are adapted to wet soil.

Drying out large gardens with severe drainage problems calls for expert assistance for everything from design to laying drainpipe. Don’t attempt complicated drainage solutions unless you have drainage experience.