How to Amend Clay Soil

Learn how to amend clay soil for better drainage, easier gardening and flourishing plants. Amending clay soil is a process that can take some time, but it’s worth it to ensure that plants will thrive for years to come.

Problems with Clay Soil

boot on a shovel digging into soggy wet clay soil
Too much clay usually means the soil is compacted. Soil compaction leads to poor water drainage, which can result in plants developing root rot. Clay soil is also difficult to cultivate, its heavy texture is also a challenge for plant root development. This can interfere with a plant’s ability to absorb the abundance of nutrients that clay has to offer.

How to Amend Clay Soil

two hands lifting loose, healthy garden soil
Is clay soil acidic or alkaline? Clay soil is typically more alkaline, but you should test your soil to be certain before making any significant adjustments. Many universities that have a Cooperative Extension Service offer soil testing. Check for an Extension Office near you. There are also home soil test kits that may be available at garden centers or can be ordered from online sources.

Improving Clay Soil with Iron Sulfate

petri dish fill with iron sulfate granules
To acidify clay soil, add ingredients like sulfur or iron sulfate. These products are easy to add; they are simply distributed at surface level and watered in. Sulfur can not only increase the acidity but will help to break up the compaction that occurs in clay soil.

Improving Clay Soil with Gypsum

hand holding dish of powdered gypsum, calcium sulfate
Gypsum, also known as calcium sulfate, is a mineral available at most garden centers. It can be easily added to clay soil to create better drainage while also improving the pH level. Like sulfur or iron sulfate, gypsum is simply sprinkled over the soil evenly and watered in.
The effects of gypsum will fade after a few months, so you may have to add amending your soil with gypsum to your regular gardening routine. Testing the soil regularly can help you determine when to amend clay soil and how much gypsum is needed.

Improving Clay Soil with Organic Matter

wheelbarrow filled with bark mulch next to a garden border
Adding organic matter seasonally (like compost, leaf mulch and manure) can help to maintain the soil pH over time. Organic matter is also one of the most important ways to improve clay soil’s friability – that is to say, creates a loose texture to the soil. Compost also adds valuable nutrients, allows air into the soil and helps water to drain more freely.

Do Not Add Sand to Clay Soil

pile of garden soil with a layer of sand on top and shovel standing in the pile
Adding sand to clay soil can create more problems than you started with. The fine clay particles surround the sand and can result in soil that is more compacted than clay alone. Worse, the combination of sand and clay can turn concrete-like when baked by the summer sun, making it extremely difficult to till and inhospitable to earthworms, insects and other microorganisms that are beneficial to soil health.

Plants For Clay Soil

For a reasonably sized garden, amending clay soil is a simple enough fix. But there are several species of ornamental plants that will grow very well in clay soil, so amendment is not the only solution. The following plant species will flourish in clay soil, saving you the effort it takes to amend the soil.

Aster

Beautiful New York Aster in full bloom, Symphyotrichum novi-belgii 'Little Pink Beauty'
Asters come in a variety of colors, need full sun and bloom in the fall. There are many perennial species available such as East Indies aster, Frikart’s aster, Michaelmas daisy, New England aster and New York aster.

Bearded Iris

beautiful field of lavender and blue bicolor bearded iris
Bearded irises come in a wide variety of colors, can grow in sun to part shade and bloom from spring into summer.

Hosta

charming variegated hosta plant in a perennial border
Hostas are known for their gorgeous leaves, unique flowers and they are super easy to grow. They grow in part shade to shade gardens and bloom in the summer.

Ornamental Grass

purple fountain grass, Pennisetum, in a flower border
Ornamental grasses vary widely, but most will tolerate clay soil, grow in sun to part shade and stay green into fall.

Heuchera

close-up of the beautiful two-toned foliage of a heuchera, coral bells, plant
Heuchera, also commonly known as coral bells, showcase colorful leaves against delicate flowers, can grow in sun to part shade and bloom from spring into fall.

Improving Clay Soil is Possible

a foot in tennis shoe on a shovel digging into soil
It’s important for anyone dealing with high-clay soil to know that the situation is not hopeless. The transformation to healthier soil usually just requires some patience. Using soil amendments and incorporating organic materials in a seasonal mulching routine are usually enough to enrich clay soil and encourage proper drainage.
For you’re short on time, smart plant choices can be used to create a lovely ornamental space without a lot of work. But a vegetable garden is worth investing the time to take corrective measures, particularly if you attempt growing root vegetables in heavy clay soil.
For more ideas on how to improve the condition of your soil see our article Straightforward Tips for Soil Improvement.
hands with shovel applying compost to young broccoli plants

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