Got heavy clay soil?
You don’t need dragon fire to break up heavy clay soil in your garden, but you do need these clay-busting plants!
These are the plants that cheer with glee when you plant them in heavy Ohio clay, and even do their part to loosen and improve clay soil so that your other garden plants can flourish.
If you want to know how to improve clay soil drainage and texture, clay breaking plants are your answer.
Annual clay loving plants increase friability, add organic matter, and open up tunnels that allow air, water, and invertebrates to move easily through the soil. They also help improve the fertility of the soil by fixing nitrogen and injecting organic matter deep into the soil where it counts.
When their annual life cycle is over, they die back and leave room for your next crop.
If you also need to know how to stop clay soil from flooding and crusting, these plants will go a long way toward healing those issues and restoring proper texture and water movement.
Note: If you have extremely compacted or waterlogged clay soil, you will get best results by tilling once to prepare for planting your clay breakers, and then not tilling – ever – after that.
Repeatedly tilling clay soil makes it more compacted and less fertile!
The no till method works best to improve clay soil, and these clay loving plants will help you turn your clay soil into perfect garden soil in no time.
If you do not wish to till at all, I recommend spreading a thick layer of wood chips or other mulch on top of the soil, and then allowing it to decompose for several months before planting your clay breakers through that mulch.
Step one of breaking up and improving clay soil is using a true clay-busting plant like one of these:
Who: Cow pea, Black-Eyed Pea
What: Frost tender legume, loves hot summer temps over 85
When: Sow it in spring after threat of frost has passed, or sow in late summer. Flowers 6 weeks after planting, 11-14 weeks to pea harvest.
Where: Use cowpeas where you plan to plant things that need nitrogen rich soil.
How: Cow peas develop thick roots that break up clay and also fix nitrogen in the soil for your fall crops. To get the most nitrogen fixation, cut the plants back shortly after they flower. If you want to harvest the peas, you’ll get less nitrogen fixation, but you can chop and drop the top growth to use as a mulch and that will help.
Why: Edible peas, nitrogen fixation, breaking up and improving clay, covering soil surface, green manure, easy kill.
Who: Austrian Winter Peas
What: Frost hardy legume, hardy to 0-10 degrees
When: Sow in autumn for winter cover, or in early spring for early crop.
Where: Sow in clay soil that needs nitrogen fixation and organic matter and where you don’t plan to grow an early spring crop. Full sun or partial shade.
How: Austrian peas create thick, lush growth and the greens are absolutely delicious! There is nothing like having access to fresh greens in the middle of winter and early spring. For maximum nitrogen fixation, cut back after flowering.
Why: Breaking clay, weed suppression, fixing nitrogen, winter cover, green manure, early fresh greens, early spring pollinator support
Who: Crimson Clover
What: Frost hardy legume, hardy to 0 degrees
When: Plant in late summer or fall
Where: Sow with an annual cereal grass, they grow well together. Crimson clover tolerates clay soil as long as it drains well. Do not use in waterlogged areas. Full sun or partial shade.
How: Crimson clover is a beautiful plant that likes to grow with annual cereal grasses. Its root nodules fix nitrogen in the soil that your garden crops will love, and, if allowed to flower, it’s beautiful red blossoms support pollinators.
Why: Nitrogen fixation in clay soil, weed suppression, biomass, organic matter, green manure, pollinator support
Who: Daikon Radish, Tillage Radish, Forage Radish
What: Frost hardy root vegetable (hardy to 20 degrees)
When: Plant in late summer/autumn as a winter cover, can be planted in early spring. Full sun to partial shade, slightly acidic soil is best.
Where: Use where you need to break up compacted soil and add significant organic matter.
How: Daikon radish roots are huge, and unlike carrots, will break right through compacted clay. When the root dies after a hard freeze, it rots and leaves large amounts of organic matter and aeration tunnels in the soil.
Daikon radishes do need more time to come to maturity than salad radishes, so keep that in mind when planning your beds. Some radish varieties can weigh up to 50lbs, so you’ll get a lot of organic matter for your buck.
Why: Natural tillage, livestock forage, increase organic matter, aerate compacted soil, break heavy clay, edible root
Who: Mighty Mustard
What: Cold hardy Brassica vegetable, cover crop blend of Kodiak, White Gold and Pacific Gold varieties. Hardy to 26 degrees (mine survived much lower temps in sheltered back yard)
When: Sow in autumn or early spring
Where: Plant in areas where you suspect soil disease or nematodes may be present. Full sun or partial shade.
How: Mighty Mustard grows like a weed and produces an incredible amount of organic matter. The plants get huge; over six feet tall, and pollinators love the profusion of bright yellow flowers in spring.
Mighty Mustard also produces biofumigant chemicals that help clear up soil disease when the plant is chopped and worked into the soil.
The big, fibrous root system does not care about compacted clay, it just keeps growing. Mighty Mustard produces a stunning amount of seed, and you will need to cut it back shortly after flowering unless you want to start a mustard farm.
Make sure you chop and drop them and then wait a few weeks after incorporating into the soil for the plant matter to break down before planting your crops.
I used the Mighty Mustard blend for my cover crop because it was designed to contain more biofumigant glucosinolates (chemicals that curtail soil pathogens) than other mustard varieties. See my video on how to chop and drop a biofumigant cover crop.
Why: Suppress weeds, biofumigant, biomass, green manure, breaking clay soil, trap crop for flea beetles and cabbage aphids, pollinator support
Once the clay breaking plants above have given you your initial breakthrough, then boost the fertility and improve the texture of your clay soil with these clay loving plants:
What: Edible seed crop, not cereal grain. Related to rhubarb, gluten free.
When: Plant anytime in late spring through late summer. Needs 4 weeks to flower, 10-12 weeks to produce seed.
Where: In clay or any other soil, avoid waterlogged areas or extreme compaction
How: Buckwheat’s fine roots are great at making clay soil more friable (loose and crumbly) and have a number of other benefits for your garden, including drawing in pollinators and beneficial insects. They mature in 4-6 weeks, and so they make a great cover crop to add biomass and improve soil very quickly.
Buckwheat also increases the amount of phosphorus in the soil and makes it more available to your garden plants.
Why: Improve friability of clay soil, add biomass and organic matter, increase soil nutrient availability, support pollinators, edible seeds
Who: Oats, Barley & Rye
What: Frost hardy annual cereal grasses
When: Plant in fall, cereal grasses will winter kill with extended freezing temps.
Where: Any clay soil that needs thick winter cover that will survive frost. Use barley in saline or alkaline soils, oats where soil may be a little too wet, and rye in dry areas. Full sun or partial shade.
How: Grasses do well in clay, and provide a lot of cover to prevent erosion, run off, and nutrient loss in winter. They have tough, dense root mats that work their way a few inches into the soil and then die off, leaving organic matter, air spaces, and room for water to move in the top layers of the soil.
I like to use crimson clover with annual oat grass planted densely in the early fall. Eventually, harsh winter temps will kill off both, but not before they have a chance to put on a lot of biomass and fix nitrogen in the soil. If your soil is extremely compacted or waterlogged, you will want to open it a bit first so that these plants can get established.
Why: Erosion control, weed suppression, adding organic matter, breaking and improving clay, nitrogen fixation, green manure
Now that you know what plants will break up and grow in Ohio clay soil, and actually improve the fertility of your clay soil, happy gardening!