Poor drainage is a major killer of our prized garden species, as stagnant water breeds disease and disaster. Plant roots struggle to breathe and slowly drown without access to enough oxygen. Assessing what type of soil you have helps you amend it better. You’ll know exactly what it needs so you can grow the best crops and ornamentals.
Well-drained soil is often found in sandy, rocky, and gritty areas. Coastal zones, alpine slopes, and deserts have the most free-draining soils of any ecosystem. Gardeners in these locales will have desirable well-draining soil, but others’ soil quality varies outside these zones.
Urban development, garden care, and the ecosystem influence soil drainage and quality. Your soil may be a mix of dirt from outside and local sources, meaning it could be different from the natural spaces around you. The best way to know your type is to do a drainage test at home. For more reliable results, you may also opt for a test kit that determines organic matter content, pH levels, and which nutrients are present.
Let’s explore a deeper understanding of drainage and how to improve it.
The Short Answer
Well-drained soil loses moisture freely and dries quickly. Soil is made up of a mixture of three particles: clay, sand, and silt. When rich in sand and silt, it’s free, or well-draining. When heavy with clay, it’s soggy when wet and compact when dry. The best ones have a good balance of all three particle sizes. If your dirt is outside the range you prefer, consider amending it or looking for plants that thrive in the conditions you’ve got already.
The Long Answer
We’ll use a drainage test to see your soil type, and then learn what to do once you know. There are a few options no matter what kind you have, so let’s get into it!
Soil Drainage Test
This is an easy drainage test will determine whether you have poorly or well-draining soil:
- Start by digging a hole two feet deep.
- Fill it with water, then let it drain. This step thoroughly soaks the area.
- After the first draining, fill up the hole again with more water.
- Check on your hole after thirty minutes, and then after an hour.
- If it drains fully in an hour, your dirt’s well-drained.
- If it takes longer than a few hours then it drains slowly.
Iowa State University teaches another variation of this test:
- Fill the hole once and let it drain.
- Then, fill it a second time and measure how much water drains after fifteen minutes.
- Multiply that number by four, and you’ll find how many inches of water drain per hour from your garden soil.
- More than an inch an hour is well-drained, and more than four inches is very well-drained.
Clay, Sand, or Silt?
Drainage and structure affect one another depending on what particles are in your dirt. Most garden species prefer loam, a perfect blending of clay, sand, and silt. Sandy and loamy soils drain well, while clay ones do not.
Test the structure by adding lots of water to an area of your garden. The next day, grab a handful of it and form a ball tightly in your hand.
- If it compacts, holds its shape, and is slimy, it’s clay.
- It’s sandy if it immediately loses shape when you open your hand.
- Loamy soils hold the ball shape, but they also crumble a bit when you poke them.
Garden Location
Your garden may be well-draining if you live in a high-elevation or sloped area. These conditions promote free-flowing moisture and air cycling below the ground. Conversely, gardeners in low elevations will find water pooling after rainstorms and irrigation.
If hills are causing water to pool at their base, you can level them out. The minute topography of your yard influences how rain travels. Watch how water drains over a year to see the effects of each season on your soil and its drainage capabilities.
Furrows allow you to take full advantage of the hills in your yard. Dig trenches three inches deep at the base of every slope. Then, plant plants near the trench. Let a hose trickle in it, and your plants will suck up moisture as it spreads. This also helps your ornamentals access free-flowing rainwater, as it pools in the trenches after rainstorms.
Break Up The Hardpan
Hardpan prevents good drainage, as it’s impervious to water and root growth. It’s a heavily compacted layer of soil resulting from natural or urban conditions. Architects and construction workers rely on compact ground to build their structures. This means many areas near our homes have a hardpan below them.
If the thick layer is close to the surface, you can till it a foot deep. Tilling may lead to more compact soils over time, as it kills the existing life belowground. An easier, less destructive method is to use drainage chimneys that let water flow freely through them. A broadfork is an excellent tool for the job.
When you plant trees or shrubs, dig a deep hole through the hardpan layer to porous ground below. As you backfill it, use humus or compost-rich soil. While the tree grows, its roots will expand into the hardpan and break it up naturally. The organically rich soil spreads microbes, worms, and fungi that colonize impermeable areas.
Dig deep for every new species you add to your yard. With enough additions, the hardpan will slowly disappear as roots spread and creep into previously uninhabitable areas. A good rule of thumb is to excavate to the depth of two shovel spades.
Amend Unfit Soils
Poorly and extremely well-draining soils are often too harsh for most roots. Drought or excessive rain causes soggy or bone-dry conditions, and your plants struggle to adapt. Compost is an easy fix that promotes drainage and balanced water retention.
Compost, or a similar organic mulch, benefits existing dirt in a few ways. Firstly, it adds nutrients that crops and ornamentals need like phosphorus, nitrogen, and calcium. It also promotes drainage with its porous structure—it mixes with existing soils, adding water and air tunnels.
Organic amendments inject mycorrhizal fungi, worms, and bacteria that partner with roots. They create channels, digest nutrients, and create cozy little homes for our garden varieties. These amendments help both sandy and clay soils balance out to be loamy. Loam is well-draining and moisture-retentive, and it’s hospitable for most species.
Right Plant, Right Spot
The easiest way to tackle well-draining or poorly-draining soil is to choose plant varieties that appreciate your garden’s current conditions. Cacti, succulents, and drought-tolerant shrubs appreciate sandy soils. Coastal, alpine, and dry forest plants like well-drained conditions.
The species that like it wet tend to grow in bogs, swamps, or rainy areas. They’re wet lovers because they experience a lot of rainfall or because water never drains where they live. They’re often evergreen or herbaceous perennials that don’t grow well with persistent droughts.
When in doubt, think about where the plant you’re growing originates. Its native conditions help clue you into the type of life it prefers. Some like it wet and cool, while others like it free-draining and bone dry. Give your plants what they want, and they’ll create a garden where others couldn’t.
Key Takeaways
- Well-drained soil applies to loam and sand, while clay-heavy soils tend to be poor draining.
- Use the drainage and structure tests to determine soil quality, and what particles it consists of.
- If your dirt isn’t what you’d prefer it to be, amend it with compost throughout the year.
- Plants prefer different conditions based on their origins—use the right ones for the plot you have.
