Exploring Landscape Setups

Soggy Garden? A French Drain Can Help

29 July 2015 by Tanya Green

Nearly everyone knows gardens need water to thrive, but like almost everything else in life you can have too much of a good thing. Water that pools in your garden and fails to drain properly can leave the soil waterlogged and cut off life-giving oxygen to the roots of your plants. Unless you are growing a bog garden, your garden space needs good drainage to keep your plants happy and thriving. One solution to drainage problems in garden areas is to install a French drain to whisk away the excess water. While it may sound intimidating, a French drain is simple to install.

What is a French drain?

A French drain is a trench filled with gravel or stones used to drain water away from a structure. It can be located near the foundation of a home or barn to prevent water from pooling near the building. In the case of gardens, the French drain surrounds the garden and channels excess water away from the plants.

Many people assume the name French drain originated in France, but this is a misconception. The French drain was named after Henry Flagg French, an agriculturist, lawyer and judge from Massachusetts. French described this method for promoting drainage in his book Farm Drainage published in 1906.  

Where do you put the French drain?

A French drain can be placed along one or both sides of your garden to funnel water away from the area. You can even add install a French drain in the middle of your garden to create a divider if you prefer. This method works well for gardens that are slightly lower than the surrounding area as the water collects at the lowest point.

For gardens that are raised in the center and lower along the sides, you will want to add a French drain along the side of the garden. The object is to collect and direct the water away from your gardening area. If the land around you garden already slopes you are in luck, but you can compensate for a lack of slope with your French drain.

How do you make a French drain?

You will need to dig a trench and fill it with gravel for the French drain. Here's how.

1. Dig a trench approximately 6 to 12 inches wide and 12 inches deep in the location you have chosen for the drain. Use care to create straight sides on the trench.
2. Slope the bottom of the trench approximately 1/8 inch per foot, if the area is not already on a slope. Water always flows from the highest point to the lowest. Your trench needs a slope for the water to flow away from the garden properly.
3. Save the soil you remove for later use.
4. Line the trench with a 3- to 4-inch layer of crushed stone, pebbles or heavy gravel.
5. Lay a 4- to 6-inch diameter perforated pipe in the trench. The pipe should run the entire length of the trench. Extending the pipe above the trench with an elbow at the beginning edge allows you to flush or clean the drain should it become clogged or sluggish. Cap the end of the pipe extending above the ground.
6. Fill in around the pipe with gravel covering the pipe by an inch or two.
7. Cover the gravel with landscape fabric. This creates a barrier that prevents dirt and debris from clogging the holes in the pipe.
8. Fill the trench to within 3 to 4 inches of the top with gravel.
9. Top with sand to complete the French drain.
10. Use the soil you removed when you dug the trench to raise the level of the garden area.

The ideal garden plot is slighted raised in the center with a gentle slope towards the sides to promote drainage, but should not be sloped so greatly that water runs off the garden before the plants get the water they need. If you would prefer professional assistance or tips, click here for more information.

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