Amending / replacing clay soil (again)

[tropicalpalms]

Location is Los Angeles, CA. I have read through zillions of threads about if and how to amend clay soil. I spend days, weeks on reasearching this subject. I'm still at a loss about how to proceed with my heavy clay soil. It appears there are several schools of thought: (1) Don't amend at all. Amending will either create 'bathtub' effects, and/or soil transitions between the amened and native soil that roots can't penetrate, thus restricting root growth, etc. Furthermore, any organic amendment will decompose over time (thus being only temporary in nature), the soil will settle and eventually compact again. (2) Amend and till under the first x feet of native soil. Just spreading on top will not change the clay soil structure (3) DON'T till but just spread compost/mulch on top periodically, and it will be 'sucked' down into the clay to keep it hopefully permenantly from compacting. (4) Don't amend, but provide for drainage (french drain etc.). Well drained clay is perfect. (5) Any sort of amending won't work in the long run. Replace all existing clay (several feet down to some deep subsoil layer) with loam. (Pay $ for long term and permanent benefit.)

Experts in all forums I read offer these seemingly contradicting experiences/conclusions. I'm lost. After reading all this, I personally would tend to create 'loam' by removing some of the clay and replacing it with 'silt' (and mixing it deep under the existing clay). We all know sand should not be mixed with clay unless the sand portion is > ca. 70%, but I didn't read about silt having this negative effect. Ideal loam is clay + silt + sand. Organic material is freely available in many cities, so buying 'potting mix' from a big box store which contains mostly organic material (together with some unknown inorganic components) would not seem to be worth the cost. However I'm unable to locate a source for the right amendment (silt? loam?) I would need to create loam. Stuff advertised as 'Topsoil' can be anything (e.g. clay mixed with organic) from what I read. Any help or thought would be appreciated. Again, the objective would be to create a *permanently* good soil in the garden to plant palms etc. without the need to amend in the future by digging (where future amendment after the garden is planted could only be spread on top but not dug under).

[DALION]

Thus my medicinal hydroponic growing system. Oh wait, I did not admit to growing anything illegal did I?

[DALION]

On a more serious note, I have come to the same conclusion as you. The "experts" are all experts from "their" experiences and many different things work. I am in situation and opted for the French drain and raised planting bed. Another Palmtalker with heavy clay told me he just dug a hole the size of the pot and stick in the palm without amending or mounding. So the right answer is to do what works for yousince that is what is best... I think.

Leo

[Jubaea]

It really depends on the environmental factors of the area and the plants being planted. There is not a "best" that works for everyone everywhere. You did not mention mounding the soil where you plant so that the area you are planting is above the surrounding area. This is kind of like a raised bed although it may erode over time. This is what I have done for planting trees, but not palms and it seemed to work well, although the mounds are eroding a bit.

[kahili]

I have heavy clay, and it seems that all the palms that I have in the ground are doing fine-some have been in the ground for 20 years. It may just be that the ones that grow in my zone can handle it, I don't know. But I do know that if you want to amend your clay-it takes time, years in fact. There is no quick remedy, imo. What I have been doing at least every two years for a long time is to spread composted leaf mulch a few inches thick over all of the planted areas. I don't till it in, there isn't enough space between the plants to do that, but I have seen a difference. When I do plant something, I do just dig the hole and plant it. I don't do anything else besides the topdressing of the mulch and slow release ferts. I also think that clay has some drawbacks, but there is also a lot of benefits with clay. I think thats true with a lot of different soils.

[tropicalpalms]

Thanks. I was afraid I wouldn't get any replies to this dead beaten old topic @Jubaea: In my specific situation, mounding would not benefit because the space in question is already sloped. But yeah, thanks for adding this method to my attempted summary of expert solutions. @kahili: Maybe that's the best way to go. (Don't think too much, just do it.) However. Some popular nice palm trees seem to take maybe 10 years from seedling to trunk forming... so - if I go the trial and error route, just to discover it won't really thrive (which again may be due to soil or a number of other factors, so it would potentially take several planting attempts to discover a statistically significant causal relationship to 'bad' soil), until it's experimentally determined if the soil should have been replaced in the first place or not - I may not live long enough to see my envisioned palm garden Hence my thought to do it right in the first place (correct permanent (=inorganic) amendment/replacement to create loam?)...

Edited March 24, 2012 by tropicalpalms

[Brett in Mission Viejo]

I have been dealing with clay for 12 years here is Mission Viejo and the top 36 inches is now a nice clay loam. I apply 4 inch thick mulch every year. I alternate every other year between a heavily composted mulch and a more 1-2 in course decorative mulch. I truly believe that with a rich organic topping, the earthworms will take care of the rest, no tilling needed. My test holes now drain now a few minutes.

[Jastin]

This thread reminds me of that song "Here I go again" by Whitesnake.

In my experience in my own 3 year old garden, visiting and talking with many people that have had clay, and taking a soil science class i've come to this conclusion:

I've dug up many things in many gardens that have different types of soil and only ever seen roots be around 32" deep max. Roots only go where water and oxygen are and clay is very dense but can work to your benefit. Raised planters are the best IMO in any soil because it gives you an instant solution to drainage. If you have a 12" high planter you just added 12" of more root space where the plant will thrive with good drainage. by putting gypsum at the bottom of the new raised planter you can also help to break the clay. Just remember to not add too much compost to your mix in you planter, even though this is really good for the plant the soil will shrink and then you just went from a 12" planter to a 8" planter. 5-10% max on the compost mixed in, you can put more on top if you would like.

Adding mulch anywhere will only help your soil so however you do that (throwing it on top or however) is fine. I dug a 5' deep hole for my Gigas and put in a vertical french drain and compost at the bottom,( before I learned about raised planters). I quickly learned that since I had no drainage I just made a huge hole for a 100 gallons to sit in. The french drain allowed me to suck the water out with a shop vac (a process)and visually check it to make sure it was not sitting in water, but it also allowed me to put massive amounts of gypsum at the bottom and now 3 years later my soil in that spot drains.

My soil was white in color 3 years ago and now when I dig it is black from the compost and brown underneath and drains fine.

Brett from Mission Viejo had a 13 year old garden of clay and he has mulched every year, you can put a hose on full blast and the water never pools up.

Adding silt is just too much of a process for me.

[Jastin]

  On 3/24/2012 at 3:17 AM, Brett in Mission Viejo said:

I have been dealing with clay for 12 years here is Mission Viejo and the top 36 inches is now a nice clay loam. I apply 4 inch thick mulch every year. I alternate every other year between a heavily composted mulch and a more 1-2 in course decorative mulch. I truly believe that with a rich organic topping, the earthworms will take care of the rest, no tilling needed. My test holes now drain now a few minutes.

Thats funny Brett, I didn't even know you wrote this. I used you as an example!

[Jastin]

  On 3/24/2012 at 3:07 AM, tropicalpalms said:

Thanks. I was afraid I wouldn't get any replies to this dead beaten old topic @Jubaea: In my specific situation, mounding would not benefit because the space in question is already sloped. But yeah, thanks for adding this method to my attempted summary of expert solutions. @kahili: Maybe that's the best way to go. (Don't think too much, just do it.) However. Some popular nice palm trees seem to take maybe 10 years from seedling to trunk forming... so - if I go the trial and error route, just to discover it won't really thrive (which again may be due to soil or a number of other factors, so it would potentially take several planting attempts to discover a statistically significant causal relationship to 'bad' soil), until it's experimentally determined if the soil should have been replaced in the first place or not - I may not live long enough to see my envisioned palm garden Hence my thought to do it right in the first place (correct permanent (=inorganic) amendment/replacement to create loam?)...

Do you have any pics of the site?

[tropicalpalms]

Edited March 24, 2012 by tropicalpalms

[Jastin]

I have a south facing 2-3 foot slope in my front yard that i mound planted and its doing great. I dug into the hill just enough to sit the box or pot level and I filled in around it. The small slope drains great and the palms are happy.

[MattyB]

downtown la is a good micro climate from what i've read. How bad is your soil? How long for a hole of water to drain?

[tropicalpalms]

  On 3/24/2012 at 5:12 AM, MattyB said:

downtown la is a good micro climate from what i've read. How bad is your soil? How long for a hole of water to drain?

I'm in North East L.A. between downtown and Glendale. According to the local weather stations, the microclimate is between downtown L.A. and the canyons of Glendale as far as minimum temps are concerned e.g. in January 2007 (absolute low was 26 deg F in North Glendale, 29 deg here if I recollect right). Min over last 100 years according to Wikipedia was 19 (!) but that was decades ago. I've read on this forum about a healthy looking Foxtail in Altadena, but I have yet to see one myself anywhere around central L.A. I've seen only one Foxtail on my way to work (10 miles through residential neighborhoods), and it was a little brown looking at the leaves' ends. But that's another topic. My soil is mostly dense heavy clay in the area in question, i.e. it bakes to cement-like clumps in summer, and sticky dense stuff after rain. I did the finger kneading test and no, the stuff doesn't crumble. I dug ca. 3 feet down to remove the root of another tree, still nothing but clay. I dug a hole and I will do the hole drainage test this weekend when we expect a downpour. During the rain last weekend I was not at home, but the hole didn't have pooled water a few hours after the rain. Yet, the stuff if really heavy clay, extremely hard to break even with a pick.

Edited March 24, 2012 by tropicalpalms

[DoomsDave]

TP!

Welcome to our 'hood, or our merry band, or Our Gang . . .

Your soil isn't unusual.

Clay can be fertile, but it takes some work to make it so.

There's a hard way and an easy way, in my experience.

The hard way is to dig down about two or three feet, pile soil to the side, and bury TONS of organics, anything you can find: dead leaves, wood chips, bad food from the 'fridge, etc. in a kind of layer cake. 2-3 feet of "stuff" then 6 inches to a foot of clay, then repeat. Then water heavy, and the stuff rots.

Or, you can build mounds and wait.

I have a garden with clay. Come visit . . . .

[palmcurry]

Tropicalpalms, welcome to palmtalk. I think your area will prove to be a decent place to grow. One advantage you have going for you is heat and your plants will grow more. There are some good gardens in your area, I believe.

First off, I don't think you can ever achieve loam if you start off with clay. Maybe with some perfect magic mix of sand, organics and who knows what, it's possible. But so is winning the lotto.

Second, water less. Roots search and dig down more when watered less. Plus water doesn't go anywhere in clay so no need to drown the roots.

Third, your soil condition is unique to you. No advice anywhere can be perfect for your soil. The only way to figure it out is through trial and error.

Where I live is at the bottom of a HUGE hill, with cold, hard grey clay in the bottom of a river basin that's stripped of top soil and condensed with river rock. It's usually 3-5 degrees F cooler here than what any media says.. I bought here to be close to my favorite surf spots, not because of the horrible growing conditions. I dug yet another hole a month ago 18" deep in my backyard and filled it with water. It took Two days to drain. Anything more than 8 hours is considered poor drainage.

First problem with hard pan is no drainage...or almost no drainage. Too much water and the roots asphyxiate. You gotta give your plants some of the advantage that plants in Hawaii have, like heat and drainage. You've already got heat. Obviously throwing X amount of mulch or compost or whatever on top of your clay and just letting it sit there is wishfull thinking. Unless you want to come back in 30 years after nature has done the work for you through time, that's a great thing to do. Otherwise, TAKE YOUR PICK AXE, some gypsum and speed up the time & evolution with your own muscle. Pick the heck out of that clay and water heavily. Then give the gypsum 3 months to have a chemical reaction with the clay to break it down. Then cover it all with lots of raw compost and pick it all over again so the broken down clay mixes with the compost. Compost breaks down clay. Busting up that clay with a pick axe opens pores for moisture and oxygen to get in, unlocking nutrients as well. Roots need air and picking clay helps oxygen passage in. Picking the compost into the clay also gets the microbes going. Microbes produce organic acids as they break down organic matter, even hard stuff like clay. Picking helps create drainage.

As said before on this forum many a time, raised beds will solve most of your clay problems. I raised beds on both picked soil and dug out basins filled in with good soil. With all the record rains we had Winter '10 I never had the 'bath tub effect' or lost any palms(plenty of damage to the home though) But I do have new pipe drains at the bottom of my property grade every 8', 1' deep. I don't know anything about well draining systems but that sounds like a proper solution.

Palms that do well in clay are a good option. As far as I know Rhopalostylus, some Ravaneas, or Acoelorraphe wrightii thrive in clay, plus many more. In my hood I see a HUGE Caryota gigas 30' tall and thriving(in a raised bed) Kentias, foxtails and of course kings and queens.

Also, I don't mulch. Mulch retains moisture. Thats great in Florida or inland California where there is plenty of heat, evaporation, ect. Clay retains moisture more than mulch ever could. If your holding moisture below and through out the roots of your plant in clay and then locking it in with an additional layer of moisture retaining mulch on top...? How is that moisture going to circulate and escape? seems to me the moisture needs more oppurtunity to evaporate in all that wet clay. When I say mulch, I don't mean compost...it's important to know the difference. Compost is soft, fresh and full of nitrates, breaks down easily. Mulch is chunky, heavy, shredded wood or bark, little to offer in nutrients and breaks down slowly. Let the deeper soil breathe and dry out, I say, so you can re-introduce water and nutrients to keep it circulating as needed.

One more trick I use. I keep a 2 -3' sharpened stick into the ground and I pull it out to check moisture level. Even when dried out on top it can be soppy at the base. Good way to figure how much to water.

Thats my two big cents Cheers

[tropicalpalms]

I think threads on this board are much more fun to read with pictures. Here are some pics of the hole I dug. I filled it with water yesterday and the water level sank 2-3 inches in 9 hours. Today the water level rose during the rain. So the water actually does stay quite long in the hole.

[i wanted to included the pics inline in the post, but didn't allow me saying wrong file extension. Read the help section of this forum but didn't find a method to upload directly from the computer]

https://picasaweb.google.com/lh/photo/t2CsiJHznLIS7PFAW_zBRjeCSR0wwF-r_Mpn1hrjuWM?feat=directlink

https://picasaweb.google.com/lh/photo/IRcUBfEI9okiEaJlV7fiTzeCSR0wwF-r_Mpn1hrjuWM?feat=directlink

https://picasaweb.google.com/lh/photo/-sgz9ysmhBc2210HVV5q6zeCSR0wwF-r_Mpn1hrjuWM?feat=directlink

I was tempted to mix the soil with more crumbly soil that I have elsewhere in the garden. However after reading up the theory, I will probably refrain from doing so and mostly backfill with the same clay. Based on the assumption that basically the *lowest* layer of soil affects the overall drainage quality of a patch of land (otherwise potentially worsening the situation by creating bathtub effect pools). So I would either replace soil (fully or mixing) down to 6-8 feet, or mostly leave the same (clay) soil on top that is further down, mechanically tilling it and moderately mixing with compost ('moderately' to avoid soil settling as I want to plant this spring already). I would be willing to spend the $ for complete replacement if it would save me a lifetime of struggling; but considering that clay has the advantage of less watering needs, I probably go the second route. thanks for all the input so far!

Edited March 26, 2012 by tropicalpalms