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| I've heard this before - that lawn grass kills or otherwise harms the beneficial mycorrhizal fungi that oaks need to be healthy.
1. Is this true?
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Follow-Up Postings:
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- Posted by ken_adrian z5 (My Page) on Thu, Jul 19, 12 at 12:35
| this is right up there with 'anonymous sources' do you have any links for this ridiculous statement ??? i think you been listening to .. well.. i dont know .. lol ... never heard of it .. weird how many oaks i see in the lawns in suburbia ... ken |
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| http://www.ehow.com/facts_7204211_can-lawns-under-oak-trees_.html That's all I could find. |
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- Posted by mad_gallica Z5 Eastern NY (My Page) on Thu, Jul 19, 12 at 13:28
| There are certain California ecosystems that have adapted to a winter wet/summer dry climate to the point that summer watering causes real problems. Since you have to water lawn in those places to keep it alive, it becomes a choice between the lawn or the trees. Anywhere that gets a reasonable amount of summer rainfall does not have this problem since the adaptation isn't there. So to answer the questions: 1. Is this true? actually yes 2. Are all oaks affected? No, only certain west coast species 3. Do certain lawn grasses do this more or less than others? If there existed a lawn grass that could handle summer drought without irrigation, that would be fine. Remember, in gardening even more than real estate, everything is Location, Location, Location. |
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| Actually some topics are universal in application, like the counterproductive aspects of top pruning at planting time and amending of planting hole backfill. |
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- Posted by formandfoliage 9b (Sunset zone 15) (My Page) on Thu, Jul 19, 12 at 15:49
| Will second the west coast issue - note that the source quoted on that link from joeschmoe was the University of California. And the issue is not that you can't grow grass under them - you can't grow anything under them that needs regular irrigation. |
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| Its false. However, I've heard that having an irrigated lawn under California's native oaks will do significant damage, I vaguely recall that a disease was involved but don't recall off-hand. |
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| It's not the grass that kills the California Oaks, it's the watering of the lawn to keep it artificially green during the native dry summers. The Oak root fungus, Armillaria, likes the extra moisture and grows very fast, killing the tree. Mike |
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| It's not just California, and it's not just oaks. Some turf grass species can pack a pretty powerful allelopathic punch and certain trees species are susceptible. Kill? I don't think so. Inhibit the development of roots, yep. The phenomenon could certainly set an already fragile tree up for severe decline. I've seen that many a time. Bermudagrass is one of the offenders, something I am very familiar with having lived in the deep south for most of my life. But there are several other common turfgrass species that are known to stunt the growth of tree roots. We need to keep in mind that we have barely scratched the surface of what there is to understand about allelopathy. These chemical interactions are MUCH more prevalent than most of us have any concept of. Most experts feel that many of our plant problems may be associated with allelopathy. Allelopathy has nothing to do with competition, with over watering, with ANYthing other than allelopathic compounds affecting the growth of other plants sharing the same rhizosphere. |
Here is a link that might be useful: Brief article
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- Posted by Dzitmoidonc 6 (My Page) on Fri, Jul 20, 12 at 7:08
| Grass killing oaks? Believable if you think oak roots stay in the top 3 inches of soil. Like the Cal. case, the water kills, not the grass. I suspect grass is blamed for other problems that killed the oaks. I am an old lazy man. I have planted over 100 species of shrubs and trees here, and have not taken the grass away. I don't mind the sight of grass collars around the trees. I hand trim the grass about 3X/year. Can't say that I have seen any problems. |
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| Actually, the all-important fine roots of trees and shrubs DO share the soil environment with turf grass roots. Look into the top six inches for the feeder roots of those massive Live Oaks, for example. Tree roots, at least those responsible for absorbing water, dissolved nutrients, and gas exchange are very shallow....anywhere from just below the surface to about 12 inches. Sooooooo....grass roots and those millions of little tree roots exchange bodily fluids 24/7. Now, that trees suffer due to over watering, pre-emergent herbicides, compaction, and a zillion other factors is true. But we shouldn't exclude allelopathic chemicals as a contributing factor in setting trees up for decline. |
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- Posted by ken_adrian z5 (My Page) on Fri, Jul 20, 12 at 17:13
| i dont believe ANYTHING that emminates from CA .. tree huggin hippie freaks have ruined the garden of eden .... lol ... and one thing for sure.. OH isnt CA..in any sense of the word ... lol ... learn something new everyday .. go figure ... hey joe .. why dont you call your county extension or forestry office and discuss such in OH ... my guess will be that they will have no clue what you are talking about .. lol ... i think you should be more concerned with OH clay.. and tree selection ... BTW.. there is a spectacular tree farm in mansfield OH ... 500 acres of oaks ... any size or type you want ... ken |
Here is a link that might be useful: hey JOE!!!
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- Posted by Dzitmoidonc 6 (My Page) on Sat, Jul 21, 12 at 7:59
| Rhizo, yes, there are a lot of feeder roots in the top 6 inches. But few grass roots get that far down, and much of the tree's root zone goes below one foot. If one has seen the toppled oaks around D.C. from the storm there, it is hard to limit the majority of roots to the top 2 ft. Some of those root balls with broken roots are 4+ft deep, and the arm-sized broken roots go how far down?. If there was that much allelopathic exchange going on, how would acorns hatch? Wouldn't grass prove an effective barrier to new oaks in lawns? From experience, I can say that acorns dropped on the lawn germinate quite well. On the other hand, I am not so smug to think my knowledge about trees can't fit in a thimble. Are there any scientific studies that have produced any likely candidates for allelopathy isolated? Or are there any studies going on with anything published? Logic would say that grasses would try to eliminate things that would eventually shade them out, but trees are relatively old in the geologic record, and the grasses are the newcomers. |
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- Posted by Snowden_Yesteryear 5 (My Page) on Sat, Jul 21, 12 at 10:24
| Grass is relatively harmless for oaks, but it is often a gateway groundcover to far more dangerous things like mushrooms or poppies. Your situation bears monitoring going forward. |
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| The original poster of this question referred us to a site that should be read carefully and then expanded upon for a better understanding of the situation. Here the reference is to installing and growing grass beneath mature oaks as in clearing land for a building site and leaving older specimen trees for shade or beauty or whatever reason. The term 'mycorrhizal fungus' gets tossed around casually but just what is it and how does it develop? MF is the detritus of plant material; dead leaves, fallen blossoms, twigs, etc. that fall to the ground and cold compost annually forming a thin, rich layer of soil and fungus which plant feeder roots search out. Not all plants utilize MF but those that do such as oaks and beech trees develop growth problems when this annual cycle is interrupted. As when a former undisturbed lot is cleared of all but a few large trees, grass is planted, mowed and raked clear of the debris so necessary for the cold composting cycle which formerly grew healthy trees. This is why the installation of a ground cover around the base of mature trees rather than grass is encouraged to allow and trap leaves and other tree droppings to collect and continue the cold composting process fairly hidden and protected by the ground cover. |
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| As mentioned, however, Nandina, that website is based on commentary from University of California, where the environment is considerably different from Ohio. I'll just share these photos from natural landscapes in New Jersey, and then you all can be the judge as to whether significant harm will NECESSARILY occur just because you have grass under oaks. The first is an Oak-Hickory forest, the second an Oak-Pine forest.
Anyway, I would argue that seeding grass under an oak with little to no actual soil disturbance is going to do little to no harm to the oak, provided that the grass has similar environmental requirements (i.e., you won't be watering it when the oak expects consistently dry weather, ect). |
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| farmitin, you missed understanding the thoughts I posted. The pictures you show have no relation to what I was trying to explain. Do you know why? Doesn't matter if they are growing in Ohio or CA. |
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| Nandina, if I'm reading your post right, my reply is that it doesn't make great sense. You imply that no trees can grow in grassy areas because of the lack of the normal decay cycle. Clearly, this isn't the case, or the many large trees surrounding homes throughout the nation, including many oaks, simply wouldn't be able to live. |
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