Shallow Roots...Deep Roots

donrawson(Z 5)February 25, 2010

Does anyone have a list of trees with shallow root systems? For example, maples, etc.

Also a list of trees with deep root systems? For example, oaks, etc.

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Who says oaks have deep root systems? Thats not necessarily always the case.

When I think of shallow rooted plants, I think of red maple and silver and freemans maples, Beeches, willows, honeylocust, pears, elms, birches sometimes sweetgums. People can add to this list

    Bookmark   February 25, 2010 at 5:14PM
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We just had some trees moved with a tree spade and Taxodium had the deepest roots of all. The rest of the trees were various oaks.

    Bookmark   February 25, 2010 at 5:54PM
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It's a common misconception that some trees have a deep root system and others a shallow one. Virtually all trees will have the bulk of their root system (95%) located very close to the soil surface -- within the top 12-18" of the soil and most roots will occur right below the soil surface. That is where necessary oxygen and most of the soil moisture and nutrients are located. Very few trees produce actual tap roots and many that are commonly considered taprooted are really only so in their youth -- they tend to outgrow that characteristic as they age. Sure, some trees will develop a deeper than normal root system in response to specific growing conditions (i.e., to access underground aquifers in very arid climates) but it is uncommon in a cultivated landscape.

Some trees are known to produce a lot of surface roots or roots that will emerge above soil level - many maples, some oaks, liquidambars, various prunus species, magnolias, etc. all share that trait, but again how likely this is to occur will depend on specific growing conditions.

    Bookmark   February 25, 2010 at 8:27PM
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brandon7 TN_zone(7)

Well written answer!

    Bookmark   February 25, 2010 at 9:03PM
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ken_adrian Adrian MI cold Z5

hey don.. slummin in the tree forum ....

peeps .. don is a hosta freak ... and a list freak .. and i love him for both ....

i will guess .. he wants to make a lists of trees ... that are favorable to garden under ... based on the aggressiveness of the root system ...

and he has been to my place a few times .... go figure on that ... lol .. who knows about his choice of friends ....

so what he MIGHT be looking for.. is a list of trees with tendencies toward fibrous root systems that interfere with the growth of the plants under ... but not limited to fibrous roots ....


maple.. especially norway .. and JM [anything with acer as its first name]

liquidamber [sweetgum]
apple [including crab, as they sucker every time you sever a root]

and now the coffee has clicked in.. and i am totally blanking.. lol ... more later.. maybe ...

when i moved here and tried to get the same answers.. i was told.. by a myriad of hosta growers.. that.. IN GENERAL ... all nut trees are favorable to being deep rooted.. and allowed companion plants .. and ergo .. i went with a lot of oak ... red, scarlet,black, shingle [imbricaria??], white [bicolor?] ... and as far as my hosta peeps have said.. jugulone is not an issue under walnut ... for hosta ... absolutely no experience with live oak though ... and i had a hickory at the old house that seemed to create no problems ...

all that said.. growing things under trees.. the root issue is not as important.. as watering.. as gal mentioned ... specific growing conditions ...

extremely mature trees .. tend to create deserts under them ... and you need to provide the water the hosta needs ... if the plant gets the water.. then they can co-habitate in a friendly way ...

but under some trees.. it is NOT going to be a plant and forget situation ... at least until the intruder achieves some level of 'establishment' ... in other words.. slap a babe in there.. and the tree might win .... as compared to inserting a mature large plant.. which can fend for itself ... or compete with the tree ... given a reasonable amount of supplemental water

getting the invader ESTABLISHED ... is imperative .. for it to try to compete on a successful basis ...

am i on point don????

does this help the rest of you give don extra trees for the lists ...

good luck


    Bookmark   February 26, 2010 at 8:18AM
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donrawson(Z 5)

Thank you, Ken, and all others who have provided information. Yes, I'm wondering which trees are known to have a less dense or fibrous root system, thus making them more suitable to grow hostas and other plants under.

Like gardengal mentioned, I've read that the root system for most trees is primarily within the top few inches of the soil. At the same time, it seems that root systems vary somewhat from tree specie to specie. Which may be one reason why it's easier to grow hostas under oaks vs. maples.

Any other input is welcome. I'm planning to do a workshop in April on growing hostas in woodland landscapes and ways to deal with root competition.

    Bookmark   February 26, 2010 at 9:17AM
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ken_adrian Adrian MI cold Z5

well then .. try this..


i created a real monster when i would fertilize just the invader.. and then walk around with my watering wand.. and just water such ..

it should NOT take long to figure out where the tree grew feeder roots.. since in digging the hole for the invader.. i truncated every tree root there ...

i may have added to the nightmare by amending the soil in the hole with some real nice peat based media ...

needless to say.... by the next season .... the maple had filled the hole with roots.. and the babe regressed in size ...

oh well.. live and learn ...



    Bookmark   February 26, 2010 at 9:36AM
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When I try to think of deep rooted trees Hickory is the first one that comes to my mind.

    Bookmark   February 26, 2010 at 10:25AM
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I assumed the OP meant surface roots. If not, refer to the other replies.

    Bookmark   February 26, 2010 at 10:49AM
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Got an idea to share. You know those 'root barriers,' often sold to either block roots from heading toward septic tanks & their leach fields, or to keep a clump of bamboo from spreading too far outward?

Some are plastic and would last a very long time. Some are geotextiles impregnanted with a chemical.

What would happen if you took a circular plastic one (such as intended to contain a bamboo clump) and planted it a few feet from the trunk of a young tree? Let's say the plastic root barrier goes down a foot & a half or two feet deep.

The idea's to create a 'hosta island.' This would not be a real cheap thing to do, and would take some work, but you could make 2 or 3 planting beds perhaps?

Would the tree inevitably send roots down under the barrier & up into your hosta island & rot it of moisture & nutrients?


    Bookmark   February 26, 2010 at 2:41PM
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Isn't the lack of taproots really an artifact of the way trees are grown commercially?

If you grow an oak from an acorn, I think it will have a deep taproot.

    Bookmark   February 26, 2010 at 5:16PM
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hortster(6a, southcentral KS)

Wow! Great thread. First, gardengal48 hit the nail on the head. Top 12-18". But, in highly compacted soils or heavy clays, even less than that - species tends to matter less than oxygen availbility. Most species have root depths dependent on the availability of oxygen. Having said that, I have watched excavations of 50-60 year old pin oak stumps with roots still heading down (in good loam soil) at 5' below the surface. Taxodium is another deep rooter. Black walnut has a tap root to China. Freeman and silver maples are horrificly shallow. In my experience, some willows have both shallow and deep roots as they are some of the species that can actually provide oxygen transfer to the roots (underwater).
As to "grow bags" and "root barriers"- show me one that really prevents ALL roots from going through other than solid plastic or concrete. But if you leave a drain hole to prevent "the bucket"...the barrier is breached. Would work for a while...
Oh, and add river birch to the list! don r - forget hostas by this one, I have.

    Bookmark   February 26, 2010 at 6:31PM
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donrawson(Z 5)

Ken, I'll send you a copy of my notes prior to the workshop. Don

    Bookmark   February 27, 2010 at 10:34AM
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