Clay soil is usually rich in mnerals. The problem is slow drainage. Adding organic materials seems to help, but as the poster above noted, not in the planting hole. Use your native soil in the planting hole and keep the amendments on top.

Like many southern California gardens, mine is clay soil, too. I have noticed improvement since adding lots of mulch. The soil is looser and there are worms now where they couldn't survive before. Gypsum is used for soils high in salts, not all clay soils. I used it because I had a white crust on the top of my soil when it rained. The neighborhood rumor was this was the site of a dairy farm before houses were built.

I did use Amend in my raised vegetable bed, and it seemed to work quite well.

Lauren I personally believe you're on the right track with just wood chip mulching. It's a slow and steady process, but it has worked wonders for my soil. Plus the worms really dig it... and more worms means better soil.

I probabaly go overboard, but I do about 6 inches of new mulch each year. The soil is pretty loamy and easy to dig now in some areas, after about 3-4 years. Clay to loam. That's pretty amazing. Not everywhere, but in some areas. Now for the rest it's just a matter of consistency and time.

Lauren, I too have clay (adobe). Roses are quite happy in it (low rainfall). The problem is lack of oxygen. Any organic matter is a plus. But organic matter that doesn't break down in 6 months is what I really like. Specifically nitrogen reinforced redwod sawdust and/or pine needles. They help the soil stay aerated even after our pounding rains have compacted it. My second favorite is dried leaves. Who'd have thought they do a better job than those expensive sacks of soil improvers? Not me.

I agree, you should amend large areas, not planting holes. But here's something I wish I I'd known years ago. It's an understanding that it's soil microbes that feed our plants and the best thing we can do as gardeners is to make our gardens hospitable for soil microbes. In other words, fertilize the soil microbes and let them feed the plants. Mulch is the best way as many thrive at the surface between soil and mulch. The soil teems with them in countless billions. Some inhabit ecosystems near plant roots and quite literally feed our plants. Here's one article that can get your started.

http://www.futuredirections.org.au/publication/the-importance-of-understanding-the-role-of-soil-microbiological-ecosystems-dr-peter-keating/

I wish I could,find the article I first came across. It was so good. So don't stop with just that one article. It's all quite a fascinating topic - literally a complex ecosystem in the soil.

If you want to learn more about the microscopic activity taking place in the soil I recommend Teaming With Microbes by Lowenfels and Lewis.

I just came from a soils class by a local nurseryman. He said DONT add organic amendment into the soil. The plants only tolerate it, not prosper in it. The short of it is that eventually it breaks down and rots causing oxygen problems in the root zone. A NASA guy said NO terrestrial plant wants to live in ground up dead tree.

So most potting soils are only good for maybe 5 months, then they start harming plants. The growers know the plants can only survive a short period before they decline in that mix. Potting up in non amended soil causes no harm. You can grow in 100 percent sand as long as you water and feed often enough. Strawberry leaves from plants grown in sand were twice the size of those in the premium potting mix! There are no overwatering issues.

Why the change from propagation in soil to wood products is a long story. However, we've all been taught to do it. But no one ever used to in the old days. Disneyland removed their riverbed soil and replaced with amended soil. After a few years, they took it all out and purchased new riverbed sandy loam and now they only mulch on top.

This is all new to me but that's the way it was for millions of years. The organic stuff stays on top where it breaks down and travels to the roots below. Roots want a purely mineral soil with as much oxygen as they can get and still be moist.

kittymoonbeam, that does seem to make sense. Limited personal experience has also showed me that top dressing compost with shredded leaves/mulch produced better results than than simply mixing some compost into the surrounding soil

I looked up "Teaming with Microbes" and it's a book and here's a brief introduction I plucked from Amazon. If that doesn't peak your interest....we'll it sure did mine.

Healthy soil teems with life—not just earthworms and insects, but a staggering multitude of bacteria, fungi, and other microorganisms. Chemical fertilizers injure the microbial life that sustains healthy plants, and the soil becomes increasingly dependent on artificial, often toxic, substances. But there is an alternative: by strengthening the soil food web—the complex world of soil-dwelling organisms—gardeners can create a nurturing environment for plants. Teaming with Microbes extols the benefits of cultivating the soil food web. It clearly explains the activities and organisms that make up the web, and explains how gardeners can cultivate the life of the soil through the use of compost, mulches, and compost tea. With Jeff Lowenfels’ help, everyone—from devotees of organic gardening techniques to weekend gardeners who simply want to grow healthy, vigorous plants—can create rich, nurturing, living soil.

Chemical fertilizers are fine as long as the concentration is low. The problem occurs when you try to apply a fast acting fert at a high rate. When the rate is low, the chemical ferts are just food for microorganisms.

Hi Nil13, while we are on the topic, is there a way to avoid phosphorus accumulation and salt build (from either organic or inorganic ferts) in ground soil? I have a 40-lb pound of inorganic slow release Citrus fertilizer (6-4-6) http://www.kellysolutions.com/erenewals/documentsubmit/KellyData/ND%5CFertilizer%5CProduct%20Label%5CVIGORO_CITRUS___AVOCADO_PLANT_FOOD_6_4_6_4_25_2011_11_06_00_AM.pdf which I plan to use on my various citrus and similar fruit trees. I've not done any kind of soil test but I suspect like many gardens in Los Angeles, nitrogen is probably the only macronutrient I really need, right? What's the proper way of using inorganic granular fertilizers such as these while at the same time avoiding excessive salt build up? The common recommendation seems to be to always use half the prescribed amounts - do you think this is an OK rule of thumb?

No, for urban soils in LA you should perform a soils test to get a baseline. The soil in LA most likely has plenty of P. If the test shows you don't have crazy high P then you can use it. Otherwise it's for container plants.

The answer is to use compost or wood chips or something as mulch and then to use organic fertilizers only.

no, that isn't the answer echolane. Organic fertilizers can be problematic as well. Manures often have too much P. You can still overload with nitrogen using organic fertilizer. It's not magic just because it is organic.

The answer is wood chip mulch and soil testing to find out what if anything you need to add.

I just stumbled on to this thread accidentally. Wow, no amendment? I too have clay soil and I am going to plant a tree. For all I know I should mix the dugged out clay soil with some compost like 50/50. But this is saying I should not be doing that?

You are better off choosing a tree that likes the soil you have then by trying to create soil that the tree will like.

50/50 is ridiculously high. Don't do that.

Yes that's a thought. However like myself I am no gardener and am not generally interested in all kinds of trees. For non-serious people we want the trees that we love. E.g. my wife wants cherry and white peach and that's pretty much it. For seasoned people like most here, we might look destined to fail :-( but we cannot force us to like different trees. Imagine her face when she discovers, hey, our peaches look like apples.

cherry and peach in zone 9 on clay? That doesn't sound like much fun. How many chill hours do you get?

If you dig a hole and fill it with nice fluffy soil surroundined by clay, it's like putting your plant in a pot. When it reaches the clay surrounding it, the roots can start circling.

@Nil13, I didn't know actually but I just checked a website (ucdavis) and it says: Hours < 45°F 857, Hours >32° and <45°F 782. What they mean I have no idea.

@lgteacher, yes. But is this particularly bad? It is probably not good but how bad it is? Because I did see people (youtube) doing it (professionals, with or without quotes.)

Yes the bathtub effect is bad. You'll have an unstable tree sitting in a tub of water. That's just begging for fungal problems. If you want trees that need good drainage and you have clay, you need to create a large raised bed or mound above the clay.

You are good wrt chill hours.

There are varieties of cherries that have a low-chill requirement such as the Royal Lee Cherry from Dave Wilson nurseries (sold in many nurseries) http://www.davewilson.com/product-information/product/royal-lee-cherry. I have such a tree and it does OK, but not great in my clay soil. It isn't vigorously growing in my soil but I do get a decent crop (if I get to it before the birds do).

There are also low-chill peach varieties that can grow in the central valley or anything colder than that. http://www.davewilson.com/home-gardens/fruit-variety-recommendations/toms-picks-winners-low-chill-southwest

Scroll to the peach section

You are in Zone 9, so you probably have a good amount of chill hours and have more options for growing whatever variety of cherry and peach tree.

@Nil13 may I know where you go to get your soil tests done? I'm seeing the costs of the soil tests, and they seem expensive and far above what I can possibly interpret (like Walllace Labs in El Segundo). I just want to know the levels of P & K, the important micronutrients and ph of my soil.

This seems like a decent option http://soiltest.cfans.umn.edu/

I use UMASS

https://ag.umass.edu/services/soil-plant-nutrient-testing-laboratory

Also, you can perform the jar test for soil structure yourself.

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-texture-jar-test.htm

I am gonna go with the raised bed idea, with a little modification. It just happens where I plant is a slope, so I cut out the area flush with the end of the slope. I guess it can be called semi-raised bed but I can see water will not stay.

Nil13, how does one know what's high and what's "crazy high" levels of P when I get my soil test back? Even if it's "high" and not "crazy high", wouldn't I create a salt-build up from using any fertilizer, organic or inorganic, with P & K after a few years?

Everything I'm reading says that phosphorus and potassium deficiencies are rare in Southern California's clay soils and such "balanced" fertilizers only need to be applied when one knows they are deficient in P & K.

May I know what nitrogen fertilizer you suggest using other than composted leaves/wood chips? Ammonium sulfate w/ urea? Milorganite?

Thank you

Just found out "Organic" Milorganite is 5-4-0

The testing lab will give you ranges for the different nutrients.

Balanced fertilizers are not what you want. You'll want urea or ammonium sulfate for nitrogen and potassium sulfate for potassium. But of course you only need to add ferts if your soil is deficient. The tests won't tell you nitrogen though. For that, you'll need to learn how to recognize nitrogen deficiency but that's easy enough.

Thanks Nil. I have ammonium sulfate already, I use that for fertilizing container blueberries but why potassium sulfate? And where do you buy it locally? I wasn't able to find that just now searching HD or Lowes. Do you find K is often needed as a supplement in urban LA soils?

potassium sulfate because it provides just potassium if you need it. Also, the sulfates will lower pH which is useful with our slightly alkaline soils. LA soils typically have enough K but some plants like citrus can use a little extra. Of course if you don't need it, don't add it.

You'll find everything at landscape supply places like Whittier Fertilizer. Home Depot doesn't carry much that's useful.

Someone here is having good results with amending clay with 50 percent sand and then topping the area with sandy loam. The nurseryman who runs Laguna Hills Nsy and gave the soils class takes the stock he buys and removes most of the mix around the roots. Then he replaces it in peat moss, perlite, pumice,sand and some charcoal. He would add more sand in the mix he sells bagged but the bags would rip or be too expensive to ship. The charcoal is there because the world's best soils have some charcoal content.

A building supply in Costa Mesa sells something called Rick's mix that is sandy loam and decomposed granite for improving clay.

I have used the best potting mixes I could buy and watch the plants die off in a year. With the mix from Laguna Hills, it doesn't happen. Now I use a mix of my own soil, sand and the Laguna Hills formula. I have been making charcoal all winter and sifting it to throw out the ash which is alkaline.

In the old days the nurseries planted in Sandy loam and sold bareroot. No one amended the holes or they planted high in large mounds or raised beds if drainage was poor. Now the wholesalers who planted in real soil are being edged out by those who plant in composted wood. The plants grow fast and are lighter to ship but eventually the breakdown of the planting material kills the plant. You can slow the process by letting the mix dry out almost completely before watering again, but it stresses the plants, especially in our warm climate.

In the old days, a nursery could water every day with no root problems at all. A nursery could keep their stock for years and water every day and feed once a month until it sold. Now it's a race to sell the plant before the mix degrades and the roots die. The nurseries have to move their stock quick before then. Even if you plant it in good soil, the plant might not make it to five years because the mix around the trunk has become poisonous to the plant. Some plants grow fast enough to get roots out beyond into good soil. Arborists use augers to drill out holes around the trunk and backfill with sand to get the oxygen into the toxic area. You can also dig into one side and replace with 100 percent soil and six months later do the other side. The formula is stay away from three times the diameter of the trunk when removing roots. That was the formula for moving plants sold in soil wrapped with burlap.

Any plant you fix needs to be shaded for two weeks. You can also help them by spraying the leaves with

1 gallon water

1 oz Karo syrup

1 oz seaweed

1 oz fish fertilizer

a little wetting agent

I hope this helps anyone trying to save a plant. I think it's rotten that plants are being sold that they know will have problems later on. People think it's their fault. The landscape reflects the trend towards only plants that can overcome the crappy potting mix and we all get taught wrongly to add this stuff to the soil at planting time.

Babcock isn't listed on the Dave Wilson site, but it's an old-fashioned white peach which is widely planted as a backyard peach in southern California. I prefer yellow peaches and currently have Mid-Pride, but I had a Babcock at a previous house in San Diego and it was extremely productive.