What To Know About Sandy Soil for Your Garden
Worried that you won't be able to grow a bountiful garden in sandy soil? Follow these tips to see how easy it can be.
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How Do You Know if You Have Sandy Soil?
If you’ve ever sat on a beach and felt the soft, warm, grainy sand beneath you, you’ll know sandy soil when you see it in your garden. If you try to squeeze a handful into a ball, it runs right through your fingers. After it rains, you rarely see puddles. You might wonder why your plants are wilting already when it just rained yesterday. These are all indications that you have sandy soil.
What is Sandy Soil?
If you observed a jar of sand under a microscope, it would look like a bunch of marbles — large, rounded particles with lots of spaces in between. Those spaces are what cause the rain and nutrients in the soil to wash right through.
Grains of sand are teeny bits of rocks, and rocks can’t hold water or nutrients like a softer piece of ground wood or humus. That’s why we use organic materials to amend sandy soil. Those materials bind the moisture and nutrients in the soil around your plants’ roots.
Benefits of Sandy Soil
You’re in luck! Sandy soil is much easier to work with than clay soil. You won’t break your back digging in or amending it. Some benefits include:
- A loose, airy texture that doesn’t become compacted and promotes good drainage.
- Root crops, like carrots, grow nice and straight, and all kinds of plants’ roots establish themselves more easily.
- Sandy soil freezes later in winter and warms faster in spring, so plants have more time to grow.
- Root rot, crown rot and other issues that arise from over-watering are not a problem.
Disadvantages of Sandy Soil
Sandy soils do require consistent intervention to grow a diverse group of plants, but if you like to work out in the garden you’ll probably enjoy these tasks. Some disadvantages of sandy soil are:
- A lack of naturally occurring nutrients. You’ll need add them yourself.
- Water and nutrients flush through quickly, requiring more frequent irrigation and the use of slow-release granular fertilizer and compost instead of water-soluble formulas.
- Water moves straight down and doesn’t spread laterally. You’ll need to position your irrigation carefully to ensure all of your plants receive enough water.
- Plants that need consistent moisture won’t thrive without amending the soil.
How to Improve Sandy Soil
Improving sandy soil requires two essential elements: Organic materials you mix in, and mulch laid on top. Let’s look at both in detail.
Remember the jar of marbles analogy? This is where adding organic materials comes in. Compost, shredded leaves, well-aged manure, finely shredded wood bark, biochar, coir and wool pellets all improve sandy soil. As they decompose, they add nutrients to your garden.
In climates where the ground freezes in winter, organic materials can be worked into the top few inches of the soil once per year in the fall or spring. Where the ground doesn’t freeze, you may need to add organic materials in fall and spring. Depending on which materials you use, a one- to three-inch-deep layer should be sufficient.
For the past 16 years, I’ve gardened atop a wooded sand dune that runs 80 feet deep under my property. My natural soil is white beach sand. To improve it, I shred my leaves every fall and lay them back into my garden beds at a depth of about three to four inches. They decompose quickly under the snow and are hardly noticeable by spring.
Additionally, I spread a one- to two-inch layer of a blend of compost, humus, manure or peat moss on top of my garden beds each spring.
After more than a decade of implementing this practice, I have transformed my beach sand into a rich, dark sandy loam to a depth of about 14 inches. Now I can grow any plants I desire because the soil holds moisture and nutrients around their roots, so they flourish. The reward is worth the effort!
Spreading mulch around your plants has many benefits, especially with sandy soil. Many people use mulch because it helps to suppress weeds and looks good while doing so. Weeds are always in competition for garden space, but weed seeds can’t sprout as easily in mulch. And when they do, they’re easy to pull up.
If you use shredded wood or bark mulch, it will also improve the texture of your soil over time as it decomposes.
Mulch prevents evaporation near the soil surface where roots are, so you won’t have to water quite as often. It also keeps the soil cooler so high temperatures won’t damage the roots. All these factors work together to create a hospitable environment for microbes and insects that break down organic materials and release nutrients into the soil.
What Not to Do If You Have Sandy Soil
If you have really sandy soil, you may be tempted to add a thick layer of “good soil” on top and plant into that. If you are only planning on growing turf grass, this might be sufficient because its roots only grow a few inches deep. But when growing ornamental or edible plants in sandy soil, covering up the problem is not a good solution.
When my house was built 35 years ago, the builder brought in a 12-inch layer of non-native clay soil to help stabilize a hill in my front yard. Over the years, this heavy soil put pressure on the beach sand below it, resulting in the sand slowly washing out. That caused the hill to sink and my retaining walls to cave in.
All this could have been avoided had the builder planted trees on the hill to stabilize the sandy soil instead of covering it up with heavy clay.
Mixing clay and sand does not create good garden soil. If you mix it in the wrong proportions, you’ll actually make low-grade concrete. Choose organic materials like compost instead and your plants will be much happier in the end.