When it comes to successful growing of shrubs, trees, perennials and many other types of plants in the landscape or garden, there's perhaps nothing more important than soil drainage. You can do everything right in terms of after-care, however, if the soil drainage doesn't meet the requirements of a specific plant, serious problems can occur. Too much or too little water can cause injury and even death to certain types of plants. Before planting, it's always best to know the soil drainage requirements of any plant or tree.


Types of Soil Drainage

(Scroll below for soil drainage testing instructions)

Before planting any type of plant in the ground make sure to know the soil drainage requirements for that type of plant.

There are 7 basic types of soil drainage. Here they are:

Excessively Dry Soil allows water to drain through very rapidly. Excessively drained soils are commonly very coarse textured, rocky, or shallow. Some are steep. Excessively drained soil is free of wetness almost immediately after any amount of rainfall or irrigation. When planting many types of plants in excessively drained soil it might be necessary to add top soil or organic matter to help retain moisture.


Well Drained Dry Soil allows water to drain from the soil rapidly. Many somewhat excessively drained soils are sandy and rapidly pervious. Some are shallow. Some are so steep that much of the water they receive is lost as runoff. These soils drain within 6 hours after heavy rain or deep-soaking irrigation.


Well Drained Soil allows water to drain from the soil readily. Well drained soils are commonly medium textured and typically hold water for no more than 24 hours after a heavy rain or deep-soaking.


Well Drained Moist soil allows water to drain from the soil somewhat slowly during some periods. They are wet for only a short time after a heavy rain or deep soaking irrigation. They commonly contain enough organic matter to hold moisture evenly for over a period of 24 to 48 hours after a heavy rain or deep-soaking irrigation.


Somewhat Poorly Drained Soil allows water to be removed slowly enough that the soil is wet for significant periods during the growing season. Wetness markedly restricts the growth of many types of plants unless artificial drainage is provided. Somewhat poorly drained soils commonly have a high water table, additional water from seepage, nearly continuous rainfall, or a combination of these. Somewhat poorly drained soil remains soggy or wet for 48 to 72 hours or more after a heavy rainfall.


Poorly Drained Soil drains so slowly that the soil is saturated periodically during the growing season or remains wet for long periods. Free water is commonly at or near the surface for long enough during the growing season that most plants, with the exception of bog or aquatic plants, cannot be grown unless the soil is artificially drained. Poor drainage results from a high water table, seepage, nearly continuous rainfall, or a combination of these. Poorly drained soil is almost always saturated, soggy or wet.


Very Poorly Drained Soil does not allow water to drain naturally which results in standing pools or bodies of water. These soils rarely if ever dry out, even during periods of drought. Water is removed from the soil so slowly that free water remains at or on the surface during most of the growing season. Unless the soil is artificially drained, most plants, with the exception of aquatic plants, cannot be grown.




How To Test Soil Drainage  

If you are uncertain about soil drainage in the area you intend to plant, it's well worth taking the time to test the drainage before planting. 


To test soil drainage:

1. Dig a hole 12" wide by 12" deep in the planting area. 

2. Fill the hole with water and let it drain. 

3. Then, after it drains, fill it with water again, but this time clock how long it takes to drain. 


In well-drained soil the water level will go down at a rate of about 1 inch an hour. A faster rate, such as in loose, sandy soil, may signal potentially dry site conditions and possibly a need to add organic matter to help retain moisture. A slower rate indicates poor draining soil and is a caution, depending on the type plant and it's moisture needs, you need to improve drainage or look for plants that are more tolerant of wet or boggy conditions.



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