Gardening in Clay: Is it Impossible to Plant in the Ground?

Brian wonders about gardening in clay:

I would like to take steps in this direction but feel stuck. My growing space consists entirely of horrible, horrible Piedmont clay. I’ve built raised beds (layered with lots of organic stuff, partly out of necessity and partly to improve the soil. But to my horror, I was moving soil recently and discovered that not only had the soil at the bottom of a bed had not improved, but the red clay monster had seemed to grow and consume some of the soil I had brought in to use. There was MORE mud than before I built the beds. Drainage is an absolute disaster.

Is a food forest hopeless in this scenario? The concept of planting in-ground seems impossible here. I also have a gently sloping space and was wondering if that should affect my attempts.

He left that comment on my brother-in-law Justin’s recent post on his Grocery Row Garden in Delaware.

That really is a difficult situation. Clay suffocates plants by preventing drainage and drowning their roots. It’s also quite hard to work, and working it makes it even harder.

My initial response to his comment was just eight words: Are there trees that grow in your area?

That’s unnecessarily wordy, though: I could have just written

Got Trees?

Forests grow in sand and in clay and everywhere in between.  They’ll even grow out of rock, if given half a chance:

The trick is to get them started.

As recommended by Piedmont Master Gardeners:

Modifying clay soils for vegetable gardens or flower beds is one thing. Tree and landscape planting however is more a matter of choosing plants that can do well in the native soil and planting them in a way that makes success most probable.

The recommended way to plant a tree or shrub is a bit different for clay than for well-drained, looser soils:

• Prepare the plant. Remove it from its container and if, as is likely, its roots are curling around the root ball, cut the roots with a knife, from top to bottom of the root ball, every 4-6 inches. This releases the roots to grow out from the plant and prevents girdling problems after planting.
• Dig the hole just large and deep enough to fit the root ball. Use the existing natural soil for backfill, without amendment. Having a consistent soil type will help the plant adapt and prevent the hole from becoming a water pool that is unable to drain into the surrounding clay.
• Elevate the top of the root ball about 2 inches above the soil line. The water needs to drain away from the plant, again to minimize pooling issues and prevent root rot.

Another thing I recommend is just growing trees from seed wherever you can. They’ll develop very strong root systems right from the beginning and their root activity and exudates improve the clay around them. Bonus points if you plant nitrogen-fixing pioneer trees – you know, the seedy trees everyone hates! – which can then be repeatedly chopped and dropped to add organic matter to the soil surface.

Most soils grow some trees. If you can’t get them growing in your yard, look around and see how nature is doing it. Chances are, she’s throwing tons of seeds around and letting the winners survive.

What About Annuals in Clay?

I have a feeling the raised beds “grew” the clay via watering from the rain and the gardener washing down the clay from the top layers and aggregating all the particles together lower down. Drainage really is a terrible issue in clay. Sometimes the only thing you can do is grow “up” and make mounds to plant upon. We did that in the sticky clay of Grenada. There was a spot we gardened that was hard as a rock when it was dry and as sticky as glue when it was wet. The papaya trees we planted in the dry season rotted and drowned in the ground when they were a few feet tall and the summer rains started falling.

It was terrible. I feel your pain.

The best luck we had was with lasagna gardening – and with the yams we grew in raised mounds of clay.

Lasagna gardening:

That video was filmed on that patch of hard-to-work, sticky black clay.

I would keep layering that organic material, and also think about installing a French drain if possible, as well as trying adding gypsum to loosen the soil.

It’s not an easy task, but I do believe the more plants and organic matter you get growing, the better the soil will become over time. Just don’t till it!

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