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| I have several shade trees that are in the lawn. We are putting in a island bed so we put cardboard down and topped with compost to kill the sod. Will this work around the trees to kill the grass or will it kill my trees too? I did this today so hopefully you can tell me yes this will work or no take the cardboard and compost off around the trees. Thanks so much. |
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| There's no way to tell what the impact will be without more information. Adding much compost (especially over a layer of cardboard) over the top of the tree's roots certainly doesn't sound like a good idea. Tree roots need oxygen to live. If enough gas exchange is blocked, roots will start dying. Also, if the compost is placed against the tree's bark, rot will likely result. Can you post a picture of your project so we can better understand what you are doing? |
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| I'm not only concerned about the cardboard over the top of fragile (and shallow) tree roots, but about how the construction of the bed might also impact those roots. Established trees just don't take kindly to having their roots disturbed by smothering, tilling, digging, and adding soil to change the grade. |
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| It would be best to remove any new beds from around the trees. It's too hard to tell based on the limited information you have provided whether or not the trees will die, or even if they will be harmed from the new bed. But as a general rule, it's a bad idea to do what you are describing. |
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- Posted by ken_adrian z5 (My Page) on Thu, Oct 13, 11 at 7:41
| i need to know what kind of trees.. how deep the mulch is.. what the mulch is.. how deep you plan on going .. and how wide a ring around the tree .... etc ... but unless you are thinking about ending up with a one foot deep bed .. i doubt a little paper and rotted compost is going to hurt any established tree ... i appreciate all the other peeps opinions.. but i have been growing my 1500 hosta under trees for 20+ years.. and as far as i know.. i havent killed a tree ... now.. if you are doing it with an earth mover, bulldozer and backhoe. ... and adding 2 feet of the stuff .... you will probably have problems ... i believe we are going to have to beg to differ here ... ken ps: now.. if its a maple or willow.. its a waste of time for a new garden bed .. in that the tree will take over all the improved soil .. faster than you can lay it down .... in my experience .... if you cant dig there due to roots.. then adding good soil above.. is only going to bring the feeder roots up into it.. rather than create a workable layer of pristine soil ... |
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| Trees are coffee trees. They are about 5 years old. The compost is not real thick. Just a thin layer to cover the cardboard and hold it in place through the winter. I'd say about four inches deep. Should I take it away or continue with the new bed? |
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- Posted by toronado3800 Z6 St. Louis (My Page) on Thu, Oct 13, 11 at 8:24
| Mary, how tall will the new bed be above the existing ground level? Personally I would round-up the grass two or three times. Are you trying to avoid the chemicals? What's the max guys, about three inches of mulch and not touching the trunk? |
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| If these trees are right in the midst of your planned landscape bed, I'd strongly suggest that you remove the cardboard. The standard rule-of-thumb specification for the depth of mulch (no cardboard) over established tree roots is 2-4 inches. Much more than that and the tree roots will be forced into growing up into that mulch layer in order to find oxygen. When that happens, root become susceptible to temperature extremes, to drought, etc. I understand that you wish to kill the grass, but if your choice is to accomplish that by excluding the sunlight from the sod, you will really be putting the trees at some risk during that process. I'd suggest some judicial misting of the area with a glyphosate (RoundUp, etc.) product (no soil drenching required) OR manual sod removal. If the area is a small one, a well-sharpened flat shovel can skin sod pretty easily while taking very little soil. |
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| Ok I pulled all the cardboard out that was under the trees. I took it out as far as the branches reached. I raked the compost to the center of the beds where nothing is planted and will spray the grass around and under the trees. How long after I spray the grass do I have to wait until I can rake the compost back under the trees. Do you think this will do it. The roundup won't harm the trees will it? Thanks for your help. I appreciated it so much! |
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| Be sure that the RoundUp doesn't come in contact with any green parts of the tree (leaves, green stems, cuts in surface roots, etc). Also be aware that it can blow around and onto the leaves if you apply it when it's windy. Other than that, it should be completely safe for the tree. I spray glyphosate (generic, plain RoundUp) around trees frequently. Different RoundUp formulations work somewhat differently. Pure glyphosate takes a couple of weeks to do its stuff, but some of the new RoundUp chemicals produce quicker results. The "extended formulas" will inhibit seed germination for quite a while. You can plant plants in the treated area as soon as the vegetation dies. I wouldn't suggest using the extended control formula for this application, even if you aren't going to plant seeds. |
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- Posted by ken_adrian z5 (My Page) on Fri, Oct 14, 11 at 9:22
| rhiz says 'mist' the roundup ... judicial no less.. lol ... roundup is not perfume.. do NOT MIST IT .... practice with your sprayer with water.. use as low a pressure as you can.. and adjust the tip so that large drops are produced.. large drops.. thru gravity.. fall to the earth.. if you atomize or mist.. it can float on the air ... in my zone .... at this time of year.. its so cold.. the grass might not look dead until next year ... but with one hour of drying.. the plant.. for all practical purposes.. is dead ... if you are z10 ... i would say .. within 3 days depending on temps .... you should notice that the grass 'seems' off color.. and at that point.. it is dead ... but all this doesnt matter ... spray the round up.. and immediately cover the area with mulch ... you dont really need to watch it die ... and whatever you miss ... will poke thru the mulch .. and you can follow up with spot spraying in a month or two ... just dont put down spray.. and then start walking thru it as you mulch.. been there.. done that .... and wondered why i had all these dead spots.. it took me a few weeks to realize they were footprints across the lawn ... lol ... what size mulch you use is important... i agree with the suggestions of wanting 2 to 4 inches depth .. but i would add .... that is AFTER SETTLING .... so with my very course mulch .. i usually go 4 to 6 inches.. because.. within a week or two.. especially after a good rain.. it will settle to 4 inches .... but if you wish to garden in this bed.. then 4 inches is a bit deep .... so i would put on 4.. so it will settle to 2 inches ... you will have to figure out what is right with what you have ... finally.. no mulch within 6 inches of the tree trunk .... that area should be bare ... ken |
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