Posted on: 30 April 2015
Flowers and shrubs enhance nearly any landscape and look their best when all their needs are met. One of the most commons needs well-meaning homeowners overlook is adequate drainage for their plantings. Without proper drainage, your plants will either shrivel up and die from lack of moisture or become waterlogged and die off from too much water. Learning to assess and correct drainage problems will save you the frustration of caring for plants that continue to perform poorly.
Choosing a Planting Site
You probably already know how important it is to choose a site that provides the light your plants need, but you may not realize how important the soil drainage is too. If you are like most people, you may assume that you can simply water moisture-loving plants more frequently to compensate for their increased watering needs. While this may work in some situations, if your soil drains too quickly no amount of supplemental watering will provide the water moisture-loving plants need. Likewise, withholding water from dense, soggy soil does little to provide the conditions drought-tolerant plants need to thrive. Choosing the right spot takes a little detective work.
- Look for an area that is slightly raised from the surrounding landscape. Sunken or depressed areas are magnets for soggy soil that can choke out the oxygen to your plants.
- Check the soil in the location. Healthy soil should be rich and dark with plenty of organic matter. Gravelly or sandy soil may drain too quickly, while soil with high amounts of clay may remain too wet.
- Assess the drainage of the soil with a soil drainage test once you have chosen a good location.
Testing Soil Drainage
Testing the drainage rate of your soil is easier than you may think. It requires a garden shovel, an old juice or vegetable can and water.
- Remove the top and bottom of an old juice or coffee can.
- Dig a hole to a depth of 2 to 3 inches shallower than the height of the can.
- Insert the can into the hole so that 2 to 3 inches extend above the soil level.
- Pack the soil around the outside of the can to secure it in place.
- Fill the can with water and allow it to drain completely.
- Refill the can with water and measure the height of the water. Measure it again in 15 minutes to determine how much water had drained into the soil.
- Multiply this number by 4 to determine the drainage rate for one hour.
A drainage rate between 1 and 6 inches an hour is recommended, says the Cornell University Extension. Soil that drains slower than 1 inch per hour is likely to remain soggy after it rains, while soil that drains faster than 6 inches an hour drains too quickly to provide your plants with the moisture they need.
Amending Soil to Improve Drainage
Adding organic matter, such as peat moss, compost or well-rotted manure to your soil improves drainage in both quick-draining and slow-draining soils. It increases the water-holding capacity of sandy or gravelly soils and slows down the drainage rate. In clay soils, organic matter lightens the soil allowing water to drain away from the roots of the plants. To amend your soil, cover the area with 3 to 6 inches of organic matter and mix it into the top six inches of the soil. The amount of organic matter you need depends on the condition of your soil.
Adjusting for Moisture-Loving or Drought Tolerant Plants
If you prefer not to amend the soil, you will need to grow plants well-suited for the area. While most plants prefer 1 to 2 inches of rain per week, some plants, such as pond and bog plants like soggy soil. If your area drains slowly and remains wet for prolonged periods, consider growing blue flag (Iris vericolor), rush (Juncus spp.) or cattails (Thypha spp.). For areas that drain quickly, choose drought-tolerant plants such as succulents, sedum, coneflowers (Echinacea spp.) or Lantana.
Whether you choose to amend the soil to meet the needs of your plants, or prefer to simply grow plants that thrive in your growing conditions makes little difference. Understanding how quickly your soil drains puts you on the road to growing a beautiful garden to enhance your landscape.Share