Drainage helps water-logged yards

The dwarf bald cypress (center) doesn’t mind the wet soil, but the garden (left) has been built up to avoid periods of saturation.


You can get too much of a good thing.

A month ago, we were watering our garden daily. Now it’s a sloppy mess. Too much water is as bad as too little. An ideal soil profile contains 50 percent particles, 25 percent water and 25 percent air.

In the Lowcountry, the soil water table is close to the surface. If you dig a hole and it fills from the bottom, your soil is saturated. Roots will not grow beyond that or end up with root rot. Either way, the plant dies.

In some areas, impermeable clay is the problem. Dig a hole and fill it with water and it may still be full the next day. In these cases, water primarily drains over the surface.

Plants like it wet. Why fight Mother Nature?

Instead, plant something that loves wet conditions such as canna, umbrella grass, iris or juncus.

Trees such as river birch, tupelo and red maple do well in wet soils. Bald cypress, too, but the knees can be a problem in residential areas.

Topsoil can be used to shape sloping mounds. This allows water to drain properly and the roots to establish quickly. In some cases, an entire berm does not need to be constructed but rather generously mounded around the tree or shrub.

However, once you change the topography of your property, consider where the water will drain. You don’t want it going toward your house and increasing the chances of mold, rot or termites. And you don’t want to send it into your neighbor’s yard. They’re usually not happy when their backyard is suddenly a swamp.

When possible, water should be diverted to acceptable outlets, such as retaining ponds or storm sewers.

When feasible, drainage can improve the soil moisture. Drainage systems are intended to create highly porous channels that move water off the surface and, in some cases, to a suitable outlet.

Tile drains use perforated corrugated pipe called drain tile to capture and remove water. That name is confusing because we’re actually talking about flexible drain tubes, or pipes, not square pieces of tile. However, the original drain system used clay tiles, and even though we now use plastic tubing, the name remains drain tile.

Perforated drain tile is typically 4 inches in diameter and allows water to enter through small slits that surround the entire pipe. They are sometimes sold with a geotextile sock to filter out contaminates to keep the drain tile functional for a longer period of time.

Trenches are typically 8 inches wide and should drop about an inch every 10 feet for suitable flow.

Once the fun of digging is finished, a couple of inches of drainage stone is placed on the bottom. Drainage gravel, such as No. 57 stone, is angular to provide plenty of pore space for percolation. The drain tile is placed in the trench and covered with remaining gravel with a minimum of 2 inches on top.

Get a weekly recap of South Carolina opinion and analysis from The Post and Courier in your inbox on Monday evenings.

It’s important that the drain tile be sloped toward an outlet where water can be discharged, such as a ditch or pond: not your neighbor’s yard.

For many people, this is the main obstacle: There is no suitable outlet. That’s where French drains can be helpful.

The French drain has nothing to do with France but the American farmer and judge Henry French.

It is a gravel-filled trench that has no outlet but designed rather to facilitate water movement off the surface and into the ground. The trench can be any dimension you want, but it’s typically 8 to 24 inches wide and up to 36 inches deep. The trench sometimes is lined with weed fabric before it is filled with drainage gravel to filter out sediment to slow the clogging of pore spaces.

In nonturf situations, it can be filled to the surface with gravel.

Drainage systems aren’t permanent solutions, but they can be effective for several years or longer, depending on conditions.

Tony Bertauski is a horticulture instructor at Trident Technical College. To give feedback, email him at tony.bertauski@tridenttech.edu.