New tree in clay soil -- did I goof?

michey1st_gw Zone 7April 25, 2014

Tree-planting newbie, here, so please bear with me in my moment of panic!

Yesterday I acquired a promising Pagoda Dogwood "Golden Shadows" in a 7 gallon pot that my local nursery special ordered for me -- hooray! It's a larger specimen than I thought I would ever end up with (and more expensive >.When I told the nursery guy about how I read about not amending the soil to avoid root girdling, he looked at me like I had 2 heads! He said he's been planting trees for 20 years and to give the tree a fighting chance for root growth in clay, amend the clay 50/50 with organic material in the hole, which should be 2x the width of the pot and to add plant-tone to the mix to encourage root growth.

He also said that with the extra width with amended soil, the tree roots wouldn't hit native soil for 2 years, and by then, the roots would be strong enough to punch through into the clay (and, in the back of my mind, I said to myself "yeah, and by then the warranty on the tree would also be over"... cynical much, Michele?!?)

Well, the (hopefully good) news is that I ignored his advice, and overruled the Mr when he said we should listen to the nursery guy, but now i'm second guessing myself.

We dug the hole 2x the width of the pot, , teased the roots of the tree, which didn't appear root bound at all) placed the tree at the proper depth (I didn't remove the existing potted soil... is that a mistake?) and as we backfilled with native clay, we compressed it with our feet (maybe a bit over-enthusiastically... yikes?), made a berm with dirt to keep water on the slight slope the tree is planted in, then mulched up to but not including the original diameter of the pot/root ball, keeping the root flare and surrounding dirt clear. After the fact, I realized we neglected to rough up the sides of the hole to loosen the compaction from shoveling... GAH!

Now i'm wondering how the poor little tree is going to get through that compressed clay and how water is going to reach the roots! I don't want to kill my tree! Did I goof? Please talk me off the ledge before I go out, dig it up, and amend my soil....

Thanks for listening!


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arktrees(6b NW Arkansas)

I have to deal with clay as well. When planting I typically plant a container plant with about 50% of the root ball above original grade, and soil mounded up to the top of the root ball. You probable did not over compact the fill soil unless you were "stomping" it.

As for the compressed sides, that is not so simple. I have forgotten to do this on occasion and everything worked out fine. BUT, my experience with dogwood is that they are slow to establish (root into surrounding so) which indicates to me that their roots are not very aggressive (penetrating). So since you just planted it yesterday, I would work on those sides. If it were a Oak, I probable wouldn't worry about it. But a dogwood, I would.

As for the rest, I see nothing wrong, though I would cover about half of the original root ball with mulch.


    Bookmark   April 25, 2014 at 9:18AM
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ken_adrian Adrian MI cold Z5

arks comments are .. i think.. lol.. encapsulated in brandons [who should pop in some time] website ... see link ..

read it.. study it... and then decide if you want a redo ... and discuss any confusion here ...

since this was just done yesterday ... you are not going to stress the tree.. any further than it is.. by redoing it ... if that is what is decided ...

soooo... either redo.. or dont.. but dont worry ...

the greatest issue.. on all transplants .. is water management thru the whole root zone planted ... in my sand.. i need to address .. how to keep the water there long enough for it to be processed .. and that is done thru inserting my finger and watering more often .. not amending ...

your issue.;. is drainage... the other side of the water management coin ... and how to shed it ... in really bad clay.. of which.. i only have your words.. and pix wont help ... is DRAINAGE ... thats an echo.. lol..

in bad clay.. you create.. thru digging .. a clay pot... and if the water never leaves.. you end up rotting them ... before the transplant can cope ...

and that is why ark.. plants have the roots.. in the clay ... where the future is.. because the tree will eventually root into the clay .... and half above.. so that the roots wont rot before it roots... the berm is made with good draining soil ...

i think that is the idea.. in a nutshell ... only to add.. that a perk test would get you a lot of info ... dig an unrelated hole.. and fill it with water .. and see how long it takes to drain.. in really bad clay.. it doesnt.. in my sand.. minutes ... and this will guide you.. as to how deep to plant it ...


Here is a link that might be useful: link

    Bookmark   April 25, 2014 at 11:02AM
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Embothrium(USDA 8 Sunset 5 WA)

The nursery guy is wrong.

As is often the case.

A few years ago I even heard an employee of a large, long-established independent garden center here tell a couple to be sure to leave the wrapping (on a field grown balled in burlap cherry tree that had been stuffed into a pot) in place at planting time.

Plants surviving obsolete planting methods does not prove that they are getting the best possible treatment.

ALWAYS plant with a uniform soil texture throughout the entire planting area, whatever you have to do to get that situation established. No pockets or zones of different texture resulting from incorporation of amendments or other mistakes.

DO put organic material on top after planting, as mulch.

This post was edited by bboy on Fri, Apr 25, 14 at 13:43

    Bookmark   April 25, 2014 at 1:40PM
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I've had trouble planting trees directly into clay and ended up replanting. New trees seem to do better with a 50/50 mix of the native soil and potting soil. I dig the holes 2 or 3 times the size of the container and about twice as deep or more. As mentioned above, you may have issues with drainage which leads to root rot. It really depends on how bad your clay is.

You may also want to avoid packing the soil too tightly around the new planting.

    Bookmark   April 25, 2014 at 1:43PM
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Embothrium(USDA 8 Sunset 5 WA)

50% organic amendments in planting hole back-fill dug out of damp clay with drainage issues is a good way to assure that trees rot after planting - you will have created a sump. Specimens so handled that grow and develop after planting have SURVIVED the amending of the planting hole, rather than benefited from it.

It is all simple physics and does not vary with soils, amendments or other circumstances. If you modify the texture of the back-fill so that it differs significantly from that of the unchanged soil around the hole, small bed or narrow planting strip how water then enters and exits the amended zone will be affected. Two common outcomes are the planting hole being chronically wetter than the surrounding soil or drier than it, placing stress on specimens until they root out of the amended area and into the soil beyond it.

This post was edited by bboy on Fri, Apr 25, 14 at 13:52

    Bookmark   April 25, 2014 at 1:50PM
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johns.coastal.patio(USDA 10b, Sunset 24)

In 1976 my summer job included tree planting at the then brand new Fullerton Arboretum. The guy there had me dig oversize, amended, holes in sandy loam. Looking back, I suspect that it would have worked either way, and that the whole thing comes down to proper watering. I like the half-in method for clay, to aid that.

(I have been back to the arboretum, but have no idea which trees, if any, are "mine." I should have taken notes.)

    Bookmark   April 25, 2014 at 2:09PM
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Re: clay-

I dig a square hole three inches deep, max, 3 to 4 ft wide, and the root collar winds up four inches or so above grade. We have thirty plus peaches on a one-year-in-the-ground-peach-tree (super sensitive to drainage). I've been pleased with the results of this method, after years of tinkering around in the dirt. M

    Bookmark   April 25, 2014 at 2:25PM
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Embothrium(USDA 8 Sunset 5 WA)

Carl E. Whitcomb's history of organized planting method evaluations using experimental controls (untreated plants providing a basis for comparison) mentions it first being noticed that amending of planting holes did not produce a benefit during the 1960s.

    Bookmark   April 25, 2014 at 2:54PM
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Embothrium(USDA 8 Sunset 5 WA)

Carl E. Whitcomb's history of organized planting method evaluations using experimental controls (untreated plants providing a basis for comparison) mentions it first being noticed that amending of planting holes did not produce a benefit during the 1960s.

    Bookmark   April 25, 2014 at 2:55PM
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Embothrium(USDA 8 Sunset 5 WA)

Carl E. Whitcomb's history of organized planting method evaluations using experimental controls (untreated plants providing a basis for comparison) mentions it first being noticed that amending of planting holes did not produce a benefit during the 1960s.

So people pushing amending of planting holes now are at least 45 years out of step.

When I used to work at garden centers the main benefit of sending people home with bags of products to mix into their planting holes was the amount these "tie-in sales" added to their purchases.

It should be noted again that small ephemeral plants such as flowering annuals and vegetables adapted to recently disturbed soils with a comparatively high organic content are a different situation. With these it is easy to establish and maintain amended soil areas that encompass the entire potential rooting area of the plants.

This post was edited by bboy on Fri, Apr 25, 14 at 15:04

    Bookmark   April 25, 2014 at 2:56PM
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Re: clay-

Making a hole only two or three inches deep, "the backfill" (all surface soil) is often already "amended" (lots of humus), particularly compared to the dirt from a narrower, deeper hole (subsoil).

Perhaps, if one were to amend the backfill in a hole where the roots are only two inches under grade, spread out far and wide, the water table created might not be a problem, maybe even advantageous by keeping the roots very evenly moist, as the humus slowly works it's way (over weeks) straight down.

It's got no other place to go.

I have experimented just this year with that; this time, placing the very bottom of the roots nearly at grade, with a wide, shallow hole, and mixing some very finely screened compost in with "the backfill", on some very "bad clay". It looks like an anthill.

I understand and have always practiced the "remove the potting soil and spread out the roots" phiolosophy, and have never amended a "hole" before. But what the hey, three more grapevines and two more peach trees are leafing out (I actually anticipate no problems, now or in the future, with such a contrary method-- but will "keep out a keen eye as the years go by").


    Bookmark   April 25, 2014 at 6:18PM
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Embothrium(USDA 8 Sunset 5 WA)

Why bother when numerous experiments conducted over many years repeatedly showed no consistent enhancement resulting from inclusion of amendments?

It's easier to throw it on afterward anyway.

    Bookmark   April 25, 2014 at 10:47PM
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"Every experiment", good Lord, I'm presenting a new experiment. I went to school for many years to present new experiments. That's what I do... experiment, and sometimes, present new experiments, bboy. M

This post was edited by Mackel-in-DFW on Sat, Apr 26, 14 at 1:30

    Bookmark   April 26, 2014 at 1:28AM
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If it's "really bad clay", it's often deficient in organic material, ANYWAY, and much easier to settle in the soil and eliminate air pockets with a sufficient amount of added organic material. If you're gonna amend it, might as well do it all above grade so NO EFFECTIVE BATHTUB can occur. M

    Bookmark   April 26, 2014 at 1:35AM
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SO YOUR NOT AMMENDING A HOLE, only making it easier for the roots to settle in on top of an unamended hole. The only dirction the roots or the compost can follow initialy is straight down Real deep and infrequent with the watering, and you get super deep roots witout risk of rot. M

    Bookmark   April 26, 2014 at 1:46AM
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You can plant the tree as high as you want, by making an unamended mound in the center of the square hole. The roots will never be in a bathtub, and nowhere to go but follow the compost and water.

I planted some kudzu and never gave it much thought, til I dug up the rhizome, and it went down to Chiner. I am into very deep root experiments, for drought tolerance and breaking hard pan. It was only an experiment amongst others, and I eliminated the 'Dzu that very moment. Weird, eh? M

    Bookmark   April 26, 2014 at 2:03AM
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davidrt28 (zone 7)

Bboy is correct. You were wise to override the bad advice of the nursery. Which one in Maryland was this?
I do believe that in some circumstances, amending backfill can produce an illusion of the plant doing better the first year or two. But your're kind of robbing Peter to pay Paul, in the long run the plant will suffer.

    Bookmark   April 26, 2014 at 4:12AM
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Embothrium(USDA 8 Sunset 5 WA)

The period of impairment is at first, before roots escape the supposedly improved soil of the amended planting hole. The period of improvement, which fools back-fill modification advocates comes after this rooting into unamended original soil outside the hole has taken place. The tree or shrub grew, so the amending must have been beneficial. Without controls, there is no basis for comparison.

Whitcomb and others planted entire plots of test subjects to see what was really going on.

    Bookmark   April 26, 2014 at 11:07AM
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Bboy, it is my understanding that the harm from amending backfill comes from the restricted lateral movement of roots through the amended soil/unamended soil interface, which causes lateral roots to encircle the trunk of the tree.

Downward moving roots don't encircle trunks.

If the bottom of the root ball sits at grade when planted, over unamended soil, whether the backfill in the mound the tree is planted in is amended or not, there is no lateral movement of the roots possible, and thus, no possibility of encircling roots.

The roots can only go straight down with this planting method, into the unamended soil underneath, and THEN laterally into the unamended, surrounding soil. The roots never have to penetrate through an inhibiting, lateral interface.

The roots in the amended mound have no place to go but down in order to find water. The mound gets dry fairly quickly compared to the surroundingsoil. So the roots are trying to escape the mound, they can only go down, and by the time the roots start spreading laterally, they are no longer surrounding the trunk, they are well under the tree and out of harm's way.

I believe this is a way to establish roots quicker, and not violate the amended hole paradigm, with no possibility of harm now or later. I base that on logic, experimentation, and having observed how much better trees seem to grow in clay when they are planted very high..

My theory is that the roots are forced to exit the immediate planting area surrounding the trunk faster when planted in a mound, and in addition, the tree can be watered much more heavily, without risk of drowning,

Maybe I should have saved this for a more theoretical thread and not in response to a newcomer's question. M

This post was edited by Mackel-in-DFW on Sat, Apr 26, 14 at 12:39

    Bookmark   April 26, 2014 at 12:36PM
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But I am getting a little tired explaining. Sometimes, I guess, you step your foot in it whether you meant to or not. M

    Bookmark   April 26, 2014 at 12:42PM
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michey1st_gw Zone 7

Thank you all for sharing your advice and experiences! The nursery in question is a large one in the DC metro area, but I don't want to call them out as they really are a nice bunch of folks and have been in business many years. I know other nurseries in the area give the same advice because a colleague of mine bought 2 trees at a different nursery last weekend and gave him the same advice re: amending the soil 50/50... which he followed. I do tend to over-research (and over-think) stuff like this, and I've been following your discussion closely. If anything, perhaps I gave this nurseryman something to dwell upon and maybe he will look it up and come to his own conclusions.

I haven't had a chance to do anything to my little tree yet -- just been too busy running around the last few days >.I'm thrilled to have these forums to bounce my ideas and questions off of... THANK YOU!

    Bookmark   April 26, 2014 at 9:02PM
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Mackel, in the mound above unamended soil, you say the roots have nowhere to go but down. On what basis do you conclude that? They might just as easily stay at the surface and circle in their little mound haven. Or expand out and be exposed to air and foot traffic. I also would be concerned about exposure to freeze and thaw cycles in cold climates. And as mentioned above, particular species will have different tendencies regarding sending roots deep.

I'm interested in this topic because here at a new construction condo complex I just moved to, the "landscapers" keep planting large mature evergreens in mounded "berms" and they keep dying. The berm architecture is admittedly not the same as a solo mound, but they are still failing.

Unfortunately, they say "oh, no problem, we'll replace them if they fail". Their fail rate is over 50%. And some have re-failed even after re-planting. Lack of proper year-1 serious irrigation is likely a big part of the problem, but one thing I noticed as I did the year-1 watering around 3 newly berm-planted Abies Concolors near my building, is that the water runs off the mound/berm easily. I assume there was a moat at planting time, but who knows. It's hard not to have control :-(

Also, I wish I read this thread and was reminded of the bathtub effect before I planted 6 new foundation shrubs last weekend. (I chucked most of the yucky builder selections). Although for a shrub, I would think the issue is less critical because the root mass is overall less expansive.

    Bookmark   April 26, 2014 at 9:32PM
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Wendy, it sounds like you're being dismissive rather than genuinely interested in the experiment.

I say this because YOU are asking ME to disprove YOUR hypothesis (that roots grow out into air) in one of thre three points you directed at me. Why don't you try to disprove my hypothesis first, and then I'll try to disprove yours, after instead of goofin' on me.

The second point you make about frost, you use mulch like any other tree, Wth? Clay mounds stay warmer longer in the fall and warm up quicker in the spring (due to sunlight).

The third point you make about how do I know whether roots will circle around in the amended mound?

(I already addressed the reasons- the mound will stay dry most of the time, because that's what mounds do, and with deep and infrequent waterings, the tree will either die or it will do what trees do, seek moisture as deep as it can go until there is no oxygen.)

-> you pull up the damn tree after the experiement is concluded, and take notes.

The last tree I pulled up that I planted this way, after a year of growth , I couldn't even find where the descending roots started to go lateral. They were a foot deep where they snapped off while pulling out the tree.. There must have been twenty or thiry of them, on a five gallon tree.

Btw, I am a biologist (a degreed scientist), not a kid doing a high school project. :) Sheesh. M

    Bookmark   April 26, 2014 at 10:33PM
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davidrt28 (zone 7)

Well, in support of Mackel: I hadn't even really read your posts closely because I just skimmed this thread, but if you're saying that on clay soil certain plants do better on mounds, I'd agree with you, though maybe we are talking about different degrees of mounding. I've had several days-long stretches of multiple thunderstorms, especially toward the end of summer, that will cause my soil - even though it's a brown loamy clay and not a red brick clay - to become innundated. This includes recent hurricanes like Irene. I've noticed that the rhodies I plant on mounds have survived these spells while ones at grade level have not, or begin to flag. In fact IIRC Rarefind's planting instructions say to plant rhodies on mounds. But in this case I think it has more to do with the root's access to oxygen than some effect on how they grow. I've rescued several rhodies that were struggling with bouts of root rot by just raising them 2-3 inches and giving a one-time treatment with an antifungal. No science or fields of test plants are required, you can visibly see that the top of that mound *doesn't* have a sheet of water on it during prolonged rains. It would be different if I were lucky to have the true prime rhododendron terroir, at least for the east coast, which would be a 15-20 degree slope. Or even steeper, such as the renown rhododendron valley at the Villa Taranto garden in 65 inches-of-rain-a-year Lago Maggiore, Italy. As it is my area set aside for them barely slopes at 1-2 degrees, probably.

This post was edited by davidrt28 on Sun, Apr 27, 14 at 16:39

    Bookmark   April 27, 2014 at 4:38PM
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