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Good soil drainage is very important to successful gardening. Without good drainage, excess water is likely to accumulate in the soil, leading to issues such as root rot, poor plant growth, and even soil erosion. While not always easy, I have found that improving soil drainage is a manageable and have found that it can transform a garden into a space where plants will thrive.

Why Soil Drainage Matters

Many people do not realise that plant roots require access to oxygen. This oxygen is accessed from the air spaces (not water) that exist in the soil. When soil retains excessive moisture, these airspaces can fill with water, depriving the plant roots from oxygen. This leads to many problems for the plant, including stunted growth, yellowing leaves, and increased vulnerability to diseases and pests. Conversely, well-draining soil allows water to move through it efficiently, ensuring that the soil airspaces exist and the roots receive the necessary oxygen and nutrients.

Signs of Poor Soil Drainage

Common signs of poor soil drainage include:

Puddles

Water should not pool on the soil surface. Persistent puddles forming after rain can indicate slow drainage.

Waterlogged Soil

Soil that does not dry out - it continues to remain wet even without the recent addition of water can be an indication that the soil is waterlogged. Often this can be due to the clay levels within your soil.

Wilting Plants 

Plants wilting is an indication that there is a plant health issue. Plants wilt when they lose more water than they uptake from the soil. It may seem surprising, but water uptake by the roots is not only dependent on the availability of water in the soil. Lack of oxygen in the soil affects the plants ability to uptake water as well - too much water (poor drainage) actually affects the plants ability to uptake water.

Algae Growth

Algae usually requires moist conditions to grow. Therefore, if you see persistent algae growth on the top of your soil, it is usually an indication that your soil has poor drainage.

Foul Odours

Waterlogged soils can lead to bacterial action that leads to foul smells arising from the soil. Again, this is mostly due to the lack of oxygen in the soil!.

Steps to improve soil drainage

Test your soil
Start by assessing your soil's texture and composition. Is it sandy or clay? Is there much organic matter in it? How friable is it - when compacted, does it easily break apart?

Soil testing kits or professional soil tests can provide valuable insights into its pH, composition, and drainage capacity. Understanding your soil's characteristics helps tailor drainage solutions to its specific needs.

Modify your soil
To improve soil drainage, consider adding organic matter like compost, well-rotted manure, or peat moss. These materials enhance soil structure, promoting better drainage in clay-heavy soils and increase water retention in sandy soils. Add these materials to the top 6-12 inches of your soil to ensure an even distribution.

If your soil is a heavy clay, the addition of gypsum (Calcium sulfate dihydrate) can also help with breaking apart the clay in more friable particles allowing water to move through it more easily. But, be aware that there are other ways that don't involve adding gypsum.

Build raised garden beds
For areas with poor natural drainage, raised garden beds are an excellent solution. These provide improved control over soil quality and drainage. Construct beds using untreated wood or other suitable materials, and fill them with a well-draining soil mix. Raised beds elevate plants above the ground, allowing good drainage and therefore preventing the problems associated with drainage issues.

Raised Garden Beds

Select suitable plants
Selecting plants adapted to your soil type and local climate is essential for minimising the impact of drainage problems. Plants native to your area often thrive in the soil conditions you have in your garden. So, research and choose plants that can thrive in your specific soil type and area, reducing the need for excessive watering or soil changes.

Grading and Sloping
Correcting your landscape's grade and slope can prevent water from pooling around your plants. Gradually slope the ground away from the base of your plants or create gentle swales to redirect excess water. Ensure that water flows away from the garden, preventing erosion and maintaining proper drainage.

Install Drainage Systems
In areas with chronic drainage problems, consider installing drainage systems like French drains and/or perforated pipes. Typically, these pipes are wrapped in landscape fabric and surrounded by gravel. They divert excess water away from the garden, preventing water-logging. Perforated pipes can also be buried beneath the soil's surface to carry water to a designated drainage area.

Use Mulch
Mulching serves as a protective barrier against soil erosion and helps maintain a moisture balance. Apply a layer of organic mulch like straw to the soil surface. When mulching, remember that it is often better to have it too thick rather than too thin - you can’t really overdo it.

Apply Mulch

Provide Regular Maintenance
Maintaining proper soil drainage is an ongoing process - it is not a situation of getting it right and then expecting it to stay that way forever!. Regularly inspect your garden for signs of drainage issues and if necessary make necessary adjustments. Remove debris that might obstruct drainage, and ensure your drainage systems remain functional. Keep an eye on weather conditions, as heavy rainfall can expose previously unnoticed drainage problems.

Good soil drainage is important to having a healthy and productive garden. Understanding the signs of poor drainage and using some of the ideas I have provided here will help you to have a wonderful garden. With patience and consistent care, you can transform your garden into a beautiful, and thriving part of your home for years to come.

About the author: Steven McLean

I am an educator and passionate gardener and traveler. Throughout my adult life, gardening has been my passion, therapy, drive and source of purpose. Even as a child I had an intrinsic interest in plants and a desire to understand what makes them grow.

I distinctly remember the moment this began - my family was on one of our regular road trips from Hervey Bay; Australia. We were driving past a field of sugar cane. Dad pulled the car over and we cut a couple of sugar cane stems and brought them home for a treat. To be honest, I didn’t really like the taste, but I did want to try and grow it; and that is exactly what I did. It was then that my fascination, interest and passion for gardening and understanding plants began.

Fast forward a few years and I studied biological sciences and began what would be a 36 year career as a Biology educator. From this, I don’t only love gardening, but I also love helping others learn about gardening. I am also always looking for new ways to develop my own gardening knowledge. I like to think I am truly a life-long learner.

Fundamental to my beliefs about education is that learning is often best done as a part of a community - learning from others, and helping others to learn. It is this type of community that I hope iCultivate will be for its members - a community of gardeners, keen to share their gardening knowledge and wanting to learn about new ways to garden - a community built on the love of gardening.

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