I add grit in the form of decomposed granite , expanded shale and scoria to my dirt. pea gravel chunks of rock, builders sand. And lots of it. Some people do 1/3 native soil 1/3 peagravel and 1/3 decomposed granite.I need to add some humus because my native soil lacks in it.

You should be able to find pumice (in place of perlite) - I'd guess 3/5 pumice, 1/5 organic matter, and 1/5 decomposed granite. That'd be a wonderful canvas to start with.

Thank you wantonamara and cactusmcharris for your answers! Do you think the size of the decomposed granite and pumice would matter much in this application? I am thinking it wouldn't matter too much as long as they are not huge chunks, but would like to hear your opinions too. Would love to be able to just buy some and put it into the garden without sifting and all that.

1/2-3/4" is ideal. The DG's also a great top dressing.

I would say, 1/4 (- 1/2)" is better and easier to find.

Jordi

I'm no expert at amending native soils, but those sizes sound way too big. Wouldn't sand do a better job of increasing drainage? With coarse gravel I'd think the native soil would simply pack into the large pore spaces created by the gravel, leaving you with the same drainage characteristics as when you started. That was my experience when mixing native soil with gravel anyways. I imagine a bit of fine gravel may be useful after sufficient sand has been added, but it seems pointless to mix soils of vastly different particle sizes.

-Chris

Chris,

Not my experience in San Diego, that's for sure - we never, ever used sand as a drainage element in planting someone's garden plants (C&S), for the same reason that it's not recommended for a potting soil ingredient anywhere- it sucketh mightily in that regard.

I had a girlfriend that used sand and pea gravel and a little bit of compost to break up OKCity clay gumbo and she used lots of sand and pea gravel and it worked for her . She successfully grows cactus and xeric natives very well. there was very little native clay soil in the mix when done with. She did use a coarse builders sand.

I forgot to say that she used 1 part 1 part 1part formula so the native soil was the minority and what was a packed gumbo became a loose soil that grew things very well. I traded with her and some plants came in the soil and believe me , if you add enough gravel it makes it loose.

I definitely agree with not using sand in containers, but growing in the ground is a completely different situation. Sandy soils are known for draining quickly and holding little water and nutrients. This is typically a bad thing for garden plants, but probably quite good for many succulents.

-Chris

My soil is non-clay, it's categorized by the Ag map as "silty loam" and I've planted everything in the straight native soil, unamended. I live on a hill, though, so drainage is rapid. Years later, everything is growing well.

I am experiencing LOAM envy. Any Loam. I want and dream of loam, even "loam on a slant". Do you think there is anything called Caliche loam?

Can anybody explain to me the difference between loam and clay?

Jordi

My understanding is that loam can be from clay, sand or silt based but has been mitigated by other factors combining characteristics. I am not an expert . When I hear clay loam or Sandy loam I think of two different things. I see that a stream has brought in silt, sand or clay sometime in melenium to moderate the pure state of either element. I really don't know too much about geology and soil mechanics. I need to go back to school.

Here is a link that might be useful: Deffinition of Loam from Wiki

Loam = porous
Clay = not porous