The importance of good drainage in your garden.
Understanding the relationship of water and air around the roots of your plants is the key to plants thriving. This applies to containerized plants as well as those planted in the ground.
All plants need water, but the water must drain away over time.
I have always said that the easiest way to kill a plant is to over water it. If the plant was growing in gravel, this would be hard to do, but in clay soils this is easy to do. Generally, the best soil for good plant health would be composed of 15% air, 35% water, and the rest soil elements like sand, clay, or silt. Now, the proportions of these soil elements are important to your drainage. Obviously, if your soils contain more sand and less clay, you will have better drainage. Also, if your site is sloped, you will generally have better drainage than a flat site.
The Jar Test
It is useful to do the “jar” test to find out what kind of soil elements are the most plentiful where you garden and grow your plants. Collect soil from a few different parts of your garden, and at different depths. Mix it thoroughly, then fill a glass jar 1/3 with this sample. Fill the jar to the top with water and shake vigorously, then let sit for several hours. You should see a few layers settling out. The sand, being the heaviest will be on the bottom, the silt in the middle, and the clay on top. Organic and woody pieces will float or sit on top of the clay layer. This test will give you an idea as to the composition of your soil.
The Squeeze Test – Step 1
An easier way to determine what type of soil that you have in your garden or landscape is the “Squeeze Test”. Dig out a shovel full of soil in your planting area, squeeze a hand full as tight as you can.
If your clod stayed together, then poke it with a stick. If it crumbles apart, congratulations…you have loam soil, the best for growing plants. If the clod stubbornly stays together when you poke it, you have clay soil and will have to amend it appropriately to be more successful growing plants.
Drainage Test – Step 1
Another test you can perform to determine what kind of drainage you have starts by digging a hole 6 inches in diameter and 1 ft. deep somewhere in your garden (preferrable somewhere you suspect the drainage to be questionable, like at the bottom of a slope, or somewhere that plants have died more often than thrived). Use a post hole digger if you have one, as this makes the perfect sized hole.
Drainage Test – Step 2
Fill the hole completely to the top with water. Wait until the water has completely drained out, then refill.
Drainage Test – Step 3
If your hole takes less than 3 hours to drain out, then you have adequate drainage for plants to thrive. If the hole takes more than 4 hours to completely drain out, then you have poor drainage and will have to rely on other methods to obtain better drainage.
Raised Bed Method
If you suspect or have determined that you have poor drainage, a raised bed planting would be your best bet. We have found that raised bed gardening not only insures great drainage, it also offers dimension and interest. A few yards of good topsoil can be piled up, easily planted, drip lines placed, and the bed mulched for very satisfying results.
Settling occurs over time
Sometimes plants are planted correctly, but settling occurs over time, causing the existing root system to be plunged into the rainy season groundwater. This can cause root rot and eventual death of a plant. If your plant or tree exhibits lack of vigor over time, and it appears to have sunk below grade, then you will know that the roots are being rotted off by fungal diseases that thrive in soggy conditions.
Install a French Drain
Another method to resolve poor drainage problems is by installing a french drain. A ditch is dug with a perforated plastic drain pipe buried in gravel. This will catch excess water and carry it away from your landscape or home. A French Drain involves more labor and expense, but if done correctly will last for years and years.
Installing a French drain may be something you want a professional to do.