Expanded Shale - where to buy?

blsrx10April 2, 2013


Newbie gardener here trying to fix up a huge slope that's in my back yard. Have been trying to read up as much as possible on this site and so far I've concluded that the soil on the slope is mostly clay and the reason it is drying up and cracking is because it lacks organic matter or nutrients.

Found many articles/posts here recommending the use of expanded shale, but all local nurseries I called have no clue what I'm asking for - most times i have to spell it out for them since they sound surprised when I ask for it. Can anyone point me to a good supplier in OC area where I can buy it for a reasonable price?

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hoovb zone 9 sunset 23

I had to look that up to see what it was. Looks like a product specific to Texas, which means you are not likely going to find it in CA. Anyway, you don't need it.

First, likely your slope is dry and cracking because it is a slope, which is going to have sharp drainage and be difficult to keep as moist as flat areas. Gravity pulls water downward and the bottom of the slope is always the most moist location. Gravity always wins. Slopes are best planted with plants that have low water needs.

Second, there's nothing wrong with clay soil. Clay soil is in fact the most nutrient-rich soil there is, and Orange County clay is no exception as this was one of the finest agricultural areas in the world before it filled up with people.

Apply a thick organic mulch to your slope, and keep it mulched. The mulch will hold in moisture as much as is possible and prevent weed growth. Over time earthworms will work the decaying mulch into the soil and make it that much better.

Aguinaga Green in Irvine is a good supplier.

One of the first things to learn about gardening is that 90% of the gardening products for sale out there you absolutely don't need. Many are touted as miracle solutions to this or that problem, but the only miracles they perform are for the seller's net worth. The only real miracle product is homemade compost, and you can make that at home for free.

    Bookmark   April 2, 2013 at 6:57PM
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What hoovb said.

What are you trying to do with the shale? How steep is your slope? What is its exposure? Any existing plants? Is erosion currently a problem? Are you inland or near the beach? Give us more info and we'll be happy to offer our experience.

    Bookmark   April 2, 2013 at 10:37PM
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Thanks hoovb and jxbrown, appreciate your responses.
The slope is roughly at 45% and erosion is not a huge concern as such so far, but have been losing shrubs since we moved in. Have attached the before and after pictures and this change is in a span of 5 months and has me worried. Please note that the entire slope gets water atleast once every two days when all the sprinklers run.



Obviously, am trying to get a handle on things before it gets worse. I am in Mission Viejo, 10 miles from beach and the slope faces east.

Have been planning on getting some new shrubs to fill up the empty spaces, but before that would like to fix the soil by adding some organic matter/mulch. Also read shale helps loosen the soil, so was trying to get that. Once done, was planning to plant some cover crop so I dont have empty dry spots.

This post was edited by blsrx10 on Wed, Apr 3, 13 at 0:48

    Bookmark   April 3, 2013 at 12:43AM
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calistoga_al ca 15 usda 9

Here I am also on a slope, most similar to yours. For me the answer was more terracing, ground covers where that was not possible. With that slope it is not possible to keep mulch in place no matter what it is made of. Al

    Bookmark   April 3, 2013 at 10:09AM
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janea(z9-Sunset 14)

Is it possible you are watering too much? I can't quite tell what you've got planted but having the sprinklers run "at least once every two days" seems like a lot to me. Just a thought!

    Bookmark   April 3, 2013 at 10:44AM
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hoovb zone 9 sunset 23

Well, one thing you need to do is get up there right after an irrigation session and see how much the root systems are actually getting. Just because you are running the irrigation doesn't mean the plant is actually getting watered. Sticking your fingers into the soil and seeing if the soil is moist or not in the spots where the plants have died (wear gloves if you have safety concerns).is the best way. Also be super careful on a wet slope. If it is not safe do not do it.

What is your irrigation system? Spray heads or what? What type of spray head? Or do you have Drip?
My slope experience is that once the plants start growing, some dry spots emerge with spray heads. So many landscape contractors put spray heads on slopes in OC and it's criminal. Then they plant shrubs that block the water to parts of the slope. Idiotic. Either areas don't get water, or much of the time the water blows away and does nothing for the plants, especially in the dry Santa Ana wind season.

If the water is not getting to the soil with spray heads look at converting to a netafim system which will save $$ on water and be a permanent solution before you spend any money on plants. Or at least change the heads to MP Rotators and adjust the heights of the heads to the mature size of the plants so that everything gets watered. Which is going to get iffy since you have Bougies and they'll get huge unless you are cutting them back regularly. Looking at that slope eventually the Bougies could envelope the entire slope and you could shut off your irrigation at that point. Once matured they will live on rain alone. The trees up there would likely not survive, however.

Also, tell us exactly what plants died and what has survived. That will help us to help you further.

If everything is actually getting watered...looking at the soil would be somewhat helpful. MV is pretty sandy but there are pockets of adobe here and there. Also do the soil-in-a-jar-shake-and-settle test and tell us what you have.

Been there and done that with slopes!

Here is a link that might be useful: what type of soil do you have?

    Bookmark   April 3, 2013 at 3:04PM
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What hoovb and Al said, again.

Five months ago was before it got cold. The grasses went dormant and the hibiscus and the bougainvilleas (I spelled that right on the first try!) stopped blooming. They will come back with the warming weather. Whack the grass to the ground now and it will look neater later, unless it is pampas grass in which case just grub the evil stuff out now (it actually looks like pink muhly grass). It does look a little dry, so get up there and check it out.

I'm putting in the Netafilm tubing. It's quite easy to work with. We've removed the lawn at our new house and replaced it with Dymondia and mixed plantings and even though we are watering heavily to get all the babies established, our water use is still down almost 40% which isn't too shabby. I expect more improvement next year.

    Bookmark   April 3, 2013 at 3:30PM
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Thanks calistoga, janea

calistoga: I think what you make sense too, but what puzzles me is when I drive around I do see street sides that seem much steeper, yet look perfectly fine covered with mulch.

janea: I think you may be right, it was programmed for 2 times a week when we moved in, i changed it to be more frequent seeing how the soil was showing some cracks.

    Bookmark   April 3, 2013 at 11:51PM
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hoovb, jxbrown
Truly appreciate taking time posting your responses.

i think you're right on the mark, I do see dry spots after the sprinklers finish their cycles right under the shrubs. I noticed the shrubs were getting all the water sprayed from the top and not much making it to the soil itself especially around them. All the sprinklers are the Hunter rotor type ones and I've tried to tweak and increase the heights so it clears the shrubs closest to them and covers more area.
Have been looking into drip irrigation stuff sold in HD, had not heard of netafim, will look into it. Am also going to stop by Aguinaga Green and pick up some compost this weekend. Thanks for the link, I will do the "soil-in-a-jar-shake-and-settle" test and post my findings.

Based on the response from this thread:
The grass I have (had) was fountain grass which pretty much dried up and had become an eye sore, so took it out. Tried to plant some yellow daisies I picked up in costco which dried up within 3 weeks, though I think (now that I know a bit more than 5 months ago) that it was mostly because that area was not getting enough water because of some overgrown shrubs blocking the sprinklers to some extent, and also when transplanting from pot to ground i dug up the hole as 1:1 instead of making twice as wide - learning from my mistakes :)

    Bookmark   April 4, 2013 at 12:11AM
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Planting new stuff on a slope is a PITA. It's hard to keep it watered to get it established. The recommended technique is to dig the hole, fill it with water and let it drain at least once, then fill it with water again and get the plant settled in. Build the best water basin that you can. Ideally pick stuff that is tough and doesn't need much water and plant it at the beginning of the wet season.

Drip irrigation can work really well on a slope because the slower delivery reduces run off, however some of the natives and Mediterraneans don't like to have their crowns continually wet from drip emitters so watering with soaker hose or overhead sprinklers may work better. I sometimes resort to temporary drip for a season or two. The Netafim is a new type of soaker hose which we've had in our groundcover since January and which I'm now adding to the other mixed beds. I've only had a couple of months with it, but so far I like it.

I've got some ceanothus that I'm trying to get established on a hill. Keeping it watered is a bear. I expect to lose some.

    Bookmark   April 4, 2013 at 1:07AM
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hoovb zone 9 sunset 23

Netafim is more of a commercial level of drip irrigation product, it will last a lot longer than the homeowner stuff. This is the product to use if you want to get it done once and never have to do it again.

That's the thing about spray irrigation on slopes with shrubbery, once the shrubs get to any size you end up with dry spots where plants die and a few plants eventually taking over because they are the ones getting all the water. You either have to keep trimming the shrubs low, which is a pain on a slope, not to mention keeping plants cut low that are not mean to be cut low, or go to groundcover type plants, or switching the irrigation method to drip.

    Bookmark   April 4, 2013 at 1:30AM
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