How Do I Build Up Tough Clay Garden Soil?

“I live in the San Fernando Valley – Woodland Hills alongside the 101 freeway which follows the Los Angeles River. The soil is horrible – topsoil atop the riverbed, which was diverted to a cement-based flow.  How do I build it up – besides gypsum – are there plants more suited to help break it up long term.” Lorraine of West Hills, California

Answer: Your soil sounds very hardpan and tough. Upon research, I found this quote: “Soil in Woodland Hills tends to be hard, compact clay…the curse of most Valley gardeners” -Melinkoff, 1987. Thankfully, there are measures that you can take to add fertility to your soil and loosen it up a bit for easier gardening.

The trouble with clayey soils is that they lack aeration, good drainage, and become very hard when dry. This disables water percolation and the fine roots of plants from gathering necessary air and moisture for top performance. Here are several measures that I would take to improve soil performance.

Add Organic Matter

For organic amendments to be effective in clay soils, they need to be evenly incorporated in quantity. Add amendments, like compost, peat moss, earthworm castings, and composted manure, into your soil at a ratio of two parts amendment to one part ground soil. Till them in or work them in with a turning fork when your clay soil is damp. Make sure they are well incorporated. The deeper you amend, the more you will improve bed performance. You might also consider berming your soils to lift them above the soil level. (Click here to learn more about berming.) Organic amendments should be added yearly to maintain good fertility.

In more arid regions like yours, the application of mulch will reduce wind erosion and hold moisture at plant root zones. (Click here for an overview of the best garden mulches and decorative covers.)

Add Mineral Components

Adding mineral components, like gypsum, can also increase the porosity and improve the structure of clay soils. A hefty application of gypsum will certainly help improve soils heavy in clay. Other minerals, like granite dust, greensand, and lime, may also be helpful in this manner. Mineral components should be applied along with organic matter for a better long-term solution to loosening and improving clay soils.

Add Topsoil

True topsoil generally contains a generous amount of loamy mineral soil with better porosity and fertility than yours because loams contain even parts sand, silt, and clay. Mix it into your beds at a 1:1 ratio, being sure to incorporate the two soils well. If you incorporate topsoil into your beds, as well as regular organic matter, you will be set!

Choose Raised Beds

Finally, you can build your beds upwards. Raised beds are an excellent choice for gardeners living in areas with poor soils. I recommend that you watch the video below that details raised bed pros and cons.

I hope that these tips help.

Happy gardening,

Jessie Keith


Fix Troubled Garden Soils with Coir

My desert garden after lots of amendment with Black Gold products high in organic matter.

My soil has never resembled that perfect loamy ground in Martha Stewart’s garden or a posh garden show. The first plot I cultivated for 18 years was dense clay too filled with rocks to resemble the soft soil all gardeners dream about. My second garden here in the desert is just the opposite. It’s sand and decomposed granite so porous it won’t make a clod. My two yards are probably more like yours: a battleground where I’ve fought to improve less than ideal soil structure. But one product has helped above others and that’s coir.

Organic matter is the one thing that solves both sandy and clay soil structural problems. Finely ground organic matter mixed into clay helps keep the tiny soil particles separated. The separation creates gaps that allow water, air, fertilizer and roots to penetrate more easily. Likewise, organic matter helps sandy soils better retain needed moisture and nutrients. Coir is an excellent supplier of organic matter for both these situations–better than even common organic additives like composted manure.

Clay-rich soil is surprisingly fertile, with high microbe populations that count it among our most productive agricultural soils. It’s just it’s high density that’s problematic. When I added truckloads of composted manure to that first garden, plants in it grew like gangbusters, but then all the amendment seemed to disappear by the next season. The high population of soil microbes literally ate the manure, and they’ll do the same in your soil too. (If only I’d had Black Gold’s Just Coir, which provides more prolonged, better structure to clay soils—especially when combined with compost.) Desert gardens soils have similar problems for different reasons.

In desert soil, organic matter serves a very different purpose because sand just won’t hold water in the root zone long enough for plants to absorb it. Every tiny bit of organic matter added to this soil acts as a miniature sponge to absorb water and nutrients to keep them handy for plants. It’s also important for creating an environment suited to microbes, which are few and need loads of compost and coir for healthy populations.

In the past, manures and compost were the corrective organic matter for troubled soils. But coir has gained popularity because it works. This byproduct of the coconut industry is proving to be a far more long-lasting soil conditioning material. It resists the quick decomposition of compost, ensuring an enduring benefit. That’s why it’s a component in many Black Gold soil amendments.

To improve your soil structure, Just Coir is a great solution for overly porous or dense ground. It’s a soft, finely ground amendment that is easy to mix in, holds water wonderfully and lasts longer than anything else.

To create a superior garden this year, mix in Black Gold All Purpose (5-5-5) OMRI Listed fertilizer into the soil with Just Coir to improve both structure and fertility of porous soils. Another option for clay soils is to blend Just Coir with Black Gold Worm Castings and fertilizer to feed the enormous microbe population as they go to work breaking down the organic matter.

Adding soil amendments before planting isn’t just a one-time thing, but an annual or bi-annual thing. It is an ongoing process that will gradually solve problems with soil structure, increases biotic activity and increase fertility. With Just Coir and a little time, gardeners can achieve great garden soils that may just verge on Martha-Stewart-perfect garden soil.