‘How to’ check drainage

September 12, 2009 at 3:58 am · Filed under 1

New gardeners are often perplexed about the enormity of gardening.  There is much to it, lots to learn, things to try and adapt to your specific needs. 

Drainage is very important to plant health.  Here is a tip for checking and understanding drainage.  First dig a hole, perhaps a foot deep and as wide.  Fill it with water and then see how long it takes to drain away into the soil.  If it drains fast (under 1/2 hour, then you have good drainage.  If it takes a whole day and it is the dry season, then you have poor drainage.  Don’t be discouraged if you have poor drainage.  You can get by with planting things very high on a mound/berm so plant roots will not drown.  Plants need air in the soil structure besides water.  When you water, you fill most of those air spaces with water, then water percolates down into lower soil levels and air returns to those spaces.  Spaces in soil are very small.  Type of soil is also related to drainage.  Sandy soils will tend to drain fast, while silt and loam drain slower, and clay, adobe drain very slowly.  If you are located on a slope, then this all changes since the natural incline precipitates better drainage!

To improve soil structure (and drainage), you can add soil amendments such as fir bark compost, etc.

Drainage is important to plants since the roots need air to breathe and stay alive, so if they drown in winter rains, or with heavy watering, there is nothing alive to support the top growth and the plant dies.  Some plants are very sensitive to drainage.  Things like cherries, peaches & nectsarines, apricots, rhododendrons & azaleas, camellias, etc. are all particular about drainage.  It needs to be very good for optimum growth and performance of the plant.  If your site is poorly drained, you can plant these choices very high on mounds/berms to give roots the best chance to succeed.

In winter it is also important to check drainage.  a high water table is also deadly to plants of many types.  They grow fine in spring summer and fall, but the next year after winter, the plant is dead for no apparent reason.  Check drainage and a high water table as a possible cause.  In winter, do the same thing, dig a hole and then see if water percolates into it by the next day.  If you can see water puddling in the hole, there is a high water table, and you will either have to make appropriate plant choices which will tolerate this condition or else plant very high.

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