DESIGNER DIRT

 Pretty does as pretty is when it comes to soil

Susan DeMersseman, Special to The Chronicle

Aug. 8, 2007Updated: Jan. 15, 2012 11:37 a.m.

It's the rare gardener who is lucky enough to have perfect soil. 

The rest of us add things, products commonly known as soil amendments. Available at most garden departments are bags full of such products - compost, topsoil, mulch, manure and the like. Many gardeners also make their own compost to enrich or amend the soil. 

Amendments are used for many reasons, but generally they loosen the soil, help retain moisture, add nitrogen and prevent compaction so that air can penetrate to the root level. 

When I began my research on soil amendments, I was interested in the more technical aspects of these designer dirts. I talked to nursery employees, people at a botanical garden and fellow gardeners. I learned about such important considerations as what product is best for clay soil or sandy soil. I learned about elements such as nitrogen, potash and phosphorous, about the concept of soil pH, and what amendments are recommended for what kinds of plants. I also bought bag after bag of all sorts of products to do my own research. 

The result of this final step was a surprise. I am a very practical person, but when it comes to dirt I must confess I am all form over function. I came to realize that I cared most about the aesthetics. Bottom line, I like beautiful dirt. From my experiments with many kinds of soil amendments I have come up with a favorite "house blend." To start with, there is nothing like grape compost to give soil a rich dark brown appearance, and as a bonus it has lots of little seeds that loosen compacted soil. Another favorite for its feel is coconut coir. It's the outer husk of coconut ground up. You might expect it to be coarse, but it is as fluffy as peat moss and much prettier - a rusty brown and wonderful to the touch. 

A third ingredient in this fruit cocktail of soil amendments is cocoa hulls. They win for smell. They are the crunchy outside husk of the cocoa bean and retain a very pleasant fragrance. Their drawback is that they, like rice hulls, tend to turn an unattractive gray when dry. They can also be a danger to pets and can form mold when they stay damp for too long. But when mixed with grape compost and coconut coir, they provide the texture and smell that makes for a perfect blend. 

I sometimes use the separate parts of my blend by themselves. The coconut coir is great to cover emerging grass seed, and grape compost sprinkled on the surface of the soil creates that freshly watered look. 

The only danger of using straight grape compost is that an absent-minded gardener may forget to sprinkle in an area that looks freshly watered. 

Other candidates in this research have been various kinds of manure. Without going into the steamy details, chicken manure is the clear winner in this category. It smells rich and organic but not stinky. 

It is also my cat's favorite. When I use a product containing it, she rolls on the lawn with great appreciation, as if I spread it just for her. 

I love the fine loose texture of sandy loam, but it is not a pretty dirt. For some projects I have mixed it in with my fruit cocktail blend, but on its own it doesn't pass the appearance test. 

I hope my plants don't mind that I have chosen dirt for its beauty and sensory qualities rather than its certain benefit to them, but so far none are dying in protest. 

For the serious gardener who cares more for function than form, my serious research indicates that every nursery has a different favorite. But the basic guidelines from many sources indicate that the perfect amendment depends upon your soil type, e.g. sandy or clay. Ask about the pH so that your acid lovers get an acid mix and your other plants get a neutral or alkaline mix. Be aware that some products are preferred for food crops because they contain no human waste. I also strongly advocate creating your own compost, but homemade compost is not right for every plant. Mine is rich and dense, but too acidic and heavy to loosen my clay soil. So I add other materials to modify it. 

When I sing the praises of my house-blend concoction, other gardeners wonder about the seeds in the grape compost. I'm pretty sure that the composting has rendered them inert, but if not, my next article may be titled "The Vineyard in My Backyard."