What it the pH of the clay? What is the climate like (precipitation). Dry, dry growing season?? How many mm do you get per year?

I'd say: use a lot of compost and depending on the acidity you could add quite some peat also. Some sand is nice in the mix I think. This should keep the soil aereated and moist. I'd dig a hole of 40 cm or so. And if it can become waterlogged It is advised to make a small hill, so the roots do not drown.

Conifers that have no problem with clay are Picea omorika, Picea abies, Picea glauca and Abies pinsapo. Pinsapo is marginal in you zone.

I am no expert BTW.

I have heavy clay but on a slope which helps drainage. Not particularly scientifically I consider the backfill as the part to amend and let the roots make their own way into the wider clay which at least will be nutrient rich. My backfill is peat compost and some loamy topsoil mixed with the original clay and some sharp sand. I also prick the bottom of the hole with a wrecking bar. I mix all the back fill in a plastic tub and if it feels right when worked with the hands, crumbly and rich then that's as much as I worry. This also means I'm not amending simply for the use of interspecimen weeds.

hi holly ....

great minds think alike.. lol ...

now a caveat.. i have sand ... i have never had clay ... but this is what i have learned from friends in your situation ...

many of my friends.. plant high ... planting about one half of the root mass in the clay ... the other half above ...

the reason is two fold ...

clay soils are usually overly wet in at least one season.. most conifers absolutely hate soggy roots ... so by lifting.. you allow at least a part of the newly planted tree have its roots above the seasonal water line ... which is a way of taking DRAINAGE into account in clay soils ...

what goes hand in hand with that is access to air ... roots need air.. as much as they need water ...

as your babe grows on its little mound.. IT WILL PUT ITS ROOTS.. were it wants too ... and that is OK ... because it will grow.. acclimated to the soil ... and grow its roots down into the clay ... unless you make such a cozy amended hole.. its roots never want to leave ... hence we tend to shy away from amending the planting hole too much ...

its all about giving it that short term leg up.. so it can survive the transplant.. and get moving ...

as you look around your neighborhood ... i am sure you see a vast number of trees ... which grow very happily in your clay soil ... again.. its all about getting that babe going ...

there are many suggestions on amendments for clay soil ... and i will leave that to the peeps that do so .. though we 'USUALLY' recommend against such ... the type of clay you have is one of the exceptions ...

but do stay away from anything that is remotely considered a fertilizer .... no fert.. no 'nure' ... compost is probably best.. a well rotted compost ... or sand.. or peagravel .... i will defer ...

so ... think along these lines:

PROPER planting ... planting high ...
PROPER watering .. which includes drainage in clay, and
PROPER mulching ...

if you can accomplish those 3 things.. taking into account your soil ... i predict 99% success rate ...

good luck

ken

ps: most conifers tend to like the soil to NEARLY dry before the next drink .. and with wet clay.. that can be very tricky .... as it is usually too wet.. and then too dry .. finding the middle ground is the trick ... and mulch is the key to that dynamic ... and inserting your finger in the soil to find out how wet or dry it is ...

ya know.. i stop to vacuum the family room and these Europeans.. hit send first.. what is that all about ...lol

i find it fascinating ... that i am sitting here at noon .... and they are checking in after dinner in Europe ....

anyway.. i digress ... ken

Thank you all for your quick responses!

jorginho - I have not ever had a soil test done but the soil here in Colorado is definitely alkaline, not acidic. The average rainfall is about 14 inches - approximately 355+ mm?

I am a bit leery of adding sand to clay soil - in my mind, sand+clay=adobe brick! - but you say it works for you, severnside? I normally just use compost for the amendment - it works a treat for perennials, but I'm not so sure about conifers, because their root zone is usually much bigger than that of perennials. I sometimes also add in some peat moss to help acidify the soil, but it is so dry and dusty I think it repels water!

I think your elevation idea might indeed be the way to plant, ken; it will keep the tree from getting "wet feet" and give the roots a chance to breathe before taking the plunge into their clay surroundings. What do you recommend for the best mulch?

Holly

Sand along with peat ammendment seems to break the clay up better but I'm surely falling foul of the too cozy hole, different soil water movement interface and bathtub problems and could pay. If your ground is flat I would adopt every recommendation from the knowledge guys.

What it the pH of the clay? What is the climate like (precipitation). Dry, dry growing season?? How many mm do you get per year?

I'd say: use a lot of compost and depending on the acidity you could add quite some peat also. Some sand is nice in the mix I think. This should keep the soil aereated and moist. I'd dig a hole of 40 cm or so. And if it can become waterlogged It is advised to make a small hill, so the roots do not drown.

Conifers that have no problem with clay are Picea omorika, Picea abies, Picea glauca and Abies pinsapo. Pinsapo is marginal in you zone.

I am no expert BTW.

I did not repost as far as I can see.

Anyways.....that is dry for many conifers. Alkaline soil: lots of peat, some compost and some sand. Should to the trick.
Put them 10 cm or so above the terrain. Dig vier small canals (10-20 cm wide, 1-2 m long) from the central pit and fill it with the same mix. May be 20 cm deep also. SO the conifer can root in there...

Good luck.

Mixing your clay with well rotted compost should attract BIG FAT WORMS . Let them do the diggin' & tunneling for you. Roots will grow in those cavities and extract whatever is useful for the plant from the stuff that came out of the backside of the worm.And yes,make sure you break up the bottom of the hole,iow,avoid the hard glazed pan effect. T.

My thinking has been that giving a young or intermediate plant a container-like mix in a hole was somehow an easier start in clay ground. It holds up somewhat until the soil difference and cozy hole theories are applied but clay alone seems a big jump from the mostly compost mix the majority of nursery plants are potted in. What about the theory of sudden big changes in root environment being a shock hazard? To amend or not would seem to be a matter of judicious estimation.

here's a thought why break your back. Could you plant trees that like or tolerate clay.

Here is a link that might be useful: Trees that tolerate clay

I can help, no argument:

What you are dealing with is quite easily said, living hell. There are things that must be done.

1) no matter how difficult it is, you will have to dig/pick axe a large hole for each planting.

2) you will need a pick axe after the hole is dug to drive it into the sides of the hole thus creating openings for the roots to go.

3) you should incorporate organic material. No sand though. Sand and clay are like the ingredients to make concrete. It's a sure death.

4) the amount of organic material (either compost or peat moss) that you use should only be mixed at a rate that is sufficient enough for you to be able to work with the backfill material. Something like 25% is where you should start.

5) Break your native soil up very well while mixing it with the organic's.

6) do plant above the soil. 4-6" mounds for 1-gallon root systems. 6" mounds for 3 and 5 gallon roots & 9" for larger. You simply as ken says, situate the plant's root-system so it's about 2" below where the top of your mound is. As you water, that extra 2" will "level off".

7) mulch. 2-3" layer and not touching the trunk.

=====

There's also called a drainage test where you dig the hole and fill it with water 1/2 way... if an hour passes and the water is still about the height you started at... then, you're going to need to do more prep-work before you plant (most if not all of the water should be gone).

You're going to need to drive (sledgehammer) a metal pole thru the middle of the hole until you have made a tunnel deep enough that you're past the "hardpan". And, then you're going to need to be able to remove whatever you use as your driving "pole". After you've accomplished this, fill that hole with large rock particles and continue as I've written above.

That's just how it is.

Dax

I lived out on the planes of Colorado in a town called Bennett. I actually did have to use a pick axe to dig a hole for a bulb bed - pick axe, fill with water, wait for it to drain away, pick ax out the now softened clay, then fill with water again. It took about 3 days to get an area dug down for a very small - like 3' by 5' - bed. At least here I can actually sink a shovel in the ground without resorting to a pick axe!

Anyway, I am going to use a combination of methods that you all have suggested - though I will probably avoid sand unless I can find some very coarse sand indeed, more like gravel - and will definitely plant above the soil level.

IpmMan - I know the best thing to do is to just plant native species which are already "made for clay" but I just can't help but want some plants/trees that don't belong here. Probably why I have some bamboos growing, along with some Japanese maples and a northern red oak.

Holly

OK so if you are determined to do this I offer this advise.
It may sound nuts but you could consider building yourself a tool called an air spade. Parts will run you about $50 and you have to rent a big diesel air compressor to power it. Mine cuts through clay much faster then a pick axe. This will allow you to mix in your soil amendments without killing your back.

Here is a link that might be useful: Build an air spade

Holly,
I'm so glad you posted here. I've been lurking for quite a while, been too chicken to post because I'm going to make an *ss of myself trying to get the plant names "correct". I've just started dabbling in conifers and have gotten great info here.
I live in Fort Lupton, 30 miles north of Denver. My ph is 7.9 and would venture a guess that your ph is similar. Most of the soils around here are 7.2 - 7.5 range. I hope that helps the folks that asked.
The soil here is absolute ack. You are correct in not wanting to overdue the peat because it's really difficult here to get it wet and keep it wet enough to help. I don't think I'd use more than 10-15% peat in what you amend with. Go with compost and don't add more than 25% amendments to your soil. Like you said, it's hard enough to dig here and the roots are going to go much further than what you can amend.
I do recommend you go to the CSU ext website and get their soil test info. I had it done a couple of years ago, it cost $25 and told me exactly what I was dealing with in my soil. it doesn't make sense to amend with what you don't need.
The high planting suggestions is a good one I'm going to use.
Barb

I'm ditching the sand, used coarse twice in the most recent plantings and only a fistful to the mix so hopefully minimal loss. Pick axing my side walls and planting high with a depression for the H2O will be new methods in. Starting tomorrow with a P.s 'Watereri'

Thanks all. And Ilex for starting the topic.

I was thinking 15-20% but that might have been an odd # "estimate" to use. I also certainly , 100% agree with what Barb had to say about everything & I also agree that smaller-particle rocks, ideally speaking... pea gravel is good. You don't want to overdo rocks in general, however. ...organic's are the preferred way to go, just as , Tunila stated. Now if there's someone on here with experience in clay like you ladies speak of, that's Tunila.

Good luck, watch your ph when selecting plants. All the other "test results" which cost $$ aren't necessary if you follow an organic-approach, i.e. you keep all your leaves from the fall, you collect needles beneath pine trees (just ask someone for their needles - I'm sure they'll be obliged to, cooperate...). and, each fall purchase the "leftover" compost and spread it over your - plantings. Go 2-3" of cover, just kind of keep the build up away from the trunk. Go get horse manure, (best thing you could do) and fill buckets of it and haul it to area's you wish to , liven up the soil. Build all this stuff up during (spring or fall or, both) - and you'll have good soil in 4-5 years...

Glad you can dig with a shovel Holly . . . oh yes, and 25 dollar soil test, that's a lot more reasonable than what my extention office referred me to... a company where the prices began at 150 bucks or so. So good.

Another product is Gypsum... but I don't know anything about it.

Dax

If you think about it, unless you can amend over a very wide area, any addition of OM or other amendments to a planting hole - wide or not - dug in clay soil is going to create a bathtub effect. The bigger the amended hole, the bigger the bathtub. Drainage is already slow and adding any sort of enriched soil (compost, peat, etc.) - which is going to be moisture retentive - will simply create an overly wet planting hole. It is an issue of how soils of different structures - amended versus non-amended - allow or hinder water percolation - referred to by soil scientists as 'soil interface'.

The best way to address planting anything in heavy, poorly draining clay soils is to plant high.....as high as you need to. Dig a very shallow but quite wide planting hole (3-5 times root ball diameter), place the root ball so that 1/3-1/2 (or more) is above grade and then mound soil - and this can be amended soil - up to cover the root ball. The wide, dished planting hole will allow for decent drainage and there is no overly absorbent amended soil in the planting hole to retain water and rot roots. It is the same principle as planting in raised beds or berms - elevated, mounded soil drains well. The roots will grow in to the clay for proper anchorage and any amendments you feel your soil requires for optimum plant growth are available more as a topdressing or mulch rather than incorporated into the hole as inappropriately absorbent backfill.

Coarse sand can be used to amend clay soil but the volume you need to add to actually improve drainage and to avoid turning the soil into concrete or adobe is so large it is typically impractical to use for this purpose. And it is also important to understand that not all clay soils are the same - some are extremely fertile and some offer better drainage than others and some retain moisture better under dry conditions.

I also grow conifers in clay, and some of them didn't make it due to the bathtub effect. These planting sites were located near gentle (and almost imperceptible) drainage swales, which channel irrigation runoff from the sprinklers, both mine and my neighbors. This is where I've found it helpful to raise the planting site.

For the rest of my yard, planting in amended holes at ground level has not created a detrimental bathtub effect. My guess is that it's because of the arid climate and very low average rainfall. The bathtub is still there, but it either doesn't fill up or stay full long enough to cause a problem.

Great thread. Thanks to Holly and Ken!

It is wonderful to get so many responses! Thanks to all of you.

IpmMan - an air spade, really? The video attached sure didn't look as if it was being used on clay soil, but it might be a great way to kill off the grass in an area where you want to place a new bed. I don't have a diesel air compressor - I do have a small electric air compressor, but I don't know that it would have the power needed for this. I think the noise would drive me nuts, too - not quite the "communing with nature" gardening that I prefer. And then there are the earthworms - at least with a shovel, though it kills or damages some earthworms when you push the blade into the ground, at least you can rescue the rest of them in the dirt that you shovel up!

My yard is seems to be primarily flat, but it is at the bottom of a slope so I do get the run off from other yards above mine - I hate to think of what chemicals that might also be coming with the run off. It has been a while, but a few years ago in late winter/early spring, we got so much rain in a two week period - very unusual for Colorado - that there was standing water in my back yard; the clay soil could only absorb so much. The standing water was primarily in the southeast corner of my yard, so I learned from that that nothing that can't tolerate occasionally wet feet should be planted in that area. I actually purchased a small portable electric sump pump and attached it to a long hose in order to siphon water out of the back yard and out the front driveway to the street!

I will try the elevation method suggested by several of you, along with breaking up the bottom of the hole with a pick axe or crowbar to avoid the hard pan effect mentioned by Tunilla. And the shallow wide planting hole idea that you gave, gardengal48, also sounds like a good idea. I won't amend the soil that is below ground level, but will cover the root ball that is above the ground level with amended soil and then cover the entire planting area with a good depth of mulch - pine straw and pine nuggets is what I will be using from now on. I do have lots of earthworms in my yard so they should help with the aeration.

treebarb - I have been meaning to get an actual PH reading for my soil for quite a few years now, but somehow never have gotten around to it. Did you send in samples from various parts of your yard, or just one sample? Did you consider trying any of the "do it yourself" kits or PH meters that seem to be available - or are they all pretty useless?

I am glad to see that others are getting useful info from this thread; I empathize with all of my fellow clay soil sufferers. I do miss the rich, black soil of Vermont - the soil there is so nice even a two year old could dig a hole two feet deep with a trowel! :p

Holly

Hi Holly. Glad to hear you too have faith in earthworms. Their presence usually means fertile soil and their effect on soil drainage and aeration is not to be underestimated.
We have a silty type of clay,full of hard limestone cobbles. In some places there are vains of pure yellow sticky clay,like plasticine . I too have lost a few plants because of the bathtub effect,but,as Sluice rightly points out,climate and topography also play an important part in the hit or miss game.
If you can get pH paper strips in the pH 5-10 range from your chemist or pharmacist,you can do an approximative pH test as follows: mix 1 part (let's say a decent mug-full) of garden soil with 2 parts of distilled water or boiled rain-water. Shake well and leave to stand for a few hours .Dip the paper strip in the solution and compare with the color chart. Not highly scientific,but pretty good for gardening purposes.Happy gardening! T.

Holly,
I was planning a windbreak planting, roughly 100 feet long and 30 feet wide, so I dug 10 holes about 6 inches deep within that planting area. I took a handful of dirt from each hole, put it in a bucket, then mixed the soil in the bucket. I took about 2 cups of soil from the bucket in a plastic bag and mailed it in.
I was pretty new to gardening and didn't have much faith in my ability to test it properly myself. I had also planted a couple of Colorado Blue Spruces in that area and they died. Since I live next to a highway I wondered about the salt and chemicals the road crews use and if it had gotten into my soil.
I asked for the standard soil and SAR (sodium eval) test. I just checked CSU's soil test site and they've gone up a bit. It's $28 for the routine garden and landscape soil test and another $6 for the SAR test.
It turned out salts were not a problem and my soil was fine for what I wanted to plant. I was a newbie and didn't know how to properly plant a tree. I've learned a bit since then, thanks to the posters on the Conifer and Tree sites here.
You'll probably be fine with the do it yourself kits, if you don't have any specific problems. I just think it's a good idea to get a baseline on your soil.
When I got my report back it included a recommendation to add 1 lb of nitrogen and 1 lb of phosphorus per 1,000 sq feet. If I hadn't done my soil test I wouldn't have known that was all the soil needed and would have been tempted to add amendments I don't need. Now I know to check the ph level a tree prefers, so I don't choose trees that won't deal with 7.9
That's the theory anyway. I'll probably still push my luck on some tree that grabs me.
Barb

tunilla, I wish our clay here was silty, though I can't imagine that silty clay is much more fun to work with than the clumping kind we have in Colorado! You can pick up a handful of soil and squeeze it together; it forms a nice sticky ball which, if allowed to dry out, becomes hard as a rock. The stuff is almost good enough to use for making pots! :p Never, ever try to work the soil when it is wet - disaster.

gardenbarb - I may break down and get the soil test; I like your idea of taking samples from various areas of the yard and mixing them up; you don't get an accurate reading for any one part of your yard, but at least you get the average PH. I certainly can't afford to send in ten samples! Or I may just try tunilla's suggestion; this will give me a rough estimate of the PH, anyway - and allow me to test more than one area - and as I don't grow plants for a living, this rough estimate will probably be good enough. Either way, I need a more accurate idea of PH than just my guess that it has to be alkaline because I'm in Colorado and thus it has a reading of 7.0+ !

Also, did you actually add the nitrogen and phosphorous as CSU recommended - and did they mean you needed to actually till it into the soil or was this some sort of top dressing they were talking about - or do you just add this when you make a new bed?

The article I linked below touches on many of the things folks here have said. It does talk about adding sand - coarse sand - as an amendment, unfortunately, but otherwise I thought it might be a useful addition to our discussion.

Holly

Here is a link that might be useful: Working with clay soils

I sure wish there was a way to edit a post on GardenWeb after it's been submitted! I do check out my posts via the preview applet before submitting them, but somehow the mistakes do manage to escape my obviously lacking editing skills.

First there was the "planes of Colorado," instead of "plains" and then there was "gardenbarb" instead of treebarb! :-o Don't know where that came from - sorry for the misnomer, treebarb.

Holly

Holly,
I don't mind. Treebarb is a silly name that I regretted almost as soon as I picked it.
Yes, I did amend using bone meal as phosphorus. I can't remember what I used for nitrogen, but I did till it in before planting.

bumping this up cuz i slandered clay in another post ... lol

boy that soil test really put barb on track ...

ken

Thank goodness for gardengal. It took a while to get a really good response. Everything she says is correct. Sorry the rest of yous.

For help fixing bad clay soils, look no further than the athletic-industrial complex. I'm not saying these products are a panacea, but they can make a big difference, and they are what field managers use to turn muck into soil in which healthy grass can be grown and on which games can be played without destroying said grass.

http://www.axisplayball.com/
http://www.turface.com/turface-products/infield-conditioners/turface-mvp
and other similar products...with a warning that Permatill has not worked as well for me
YES, you ought to use a serious tiller to get the most out of this stuff (think Barreto). It is expensive, but if you use it correctly, the fix is permanent.

NOTE that this is different from a "personal recommendation". I would only "recommend" something I was certain would help in almost every situation. I am not sure of that: as gardengal says, there are many types of clay soil. This is more a "take note". Products like this have proved invaluable for me, in my clay soils, YMMV. (your mileage may vary)