Fence Post - Concrete leach ?

Discussion in 'Garden Projects and DIY' started by ricky101, Nov 21, 2017.

  1. ricky101

    ricky101 Total Gardener

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    Hi,

    When we put up a fence the other year the posts were set into holes about 2ft deep and filled with the typical dry post mix and watered it.

    A months or so later a nearby ( within 3ft ) golden private bush and a 5ft high holly bush both started curling some leaves and then turning brown.
    The private survived but the holly seemed too far gone.

    We suspected, but not sure, if it was the heat and / or lime from the cement that caused it.

    We are looking to put up another run of fencing with various bushes nearby again.

    The only thing we could think of was to dig the hole and take some strong rubble bags and line the hole with them so retaining the cement.

    Any thoughts as if this will work or any other methods to try ?
     
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    • clanless

      clanless Total Gardener

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      You could try ground spikes - they hammer into the ground and have a socket on top to place the posts into. I've used them before - but added a small amount of concrete to further stabilise them. The advantage being that when the posts fail - they are easy to replace :blue thumb:.

      From my experience, the postcrete goes off fairly quickly - I wouldn't have thought that there was enough time for the plants to take up any of its ingredients before it sets hard.

      Perhaps in digging the holes the plant roots were damaged or it was just coincidence - you do mention that heat may have been a factor?:)
       
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      • Verdun

        Verdun Passionate gardener

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        Ricki, the lime in the cement is the culprit I think. Particularly fatal when done near ericaceous plants of course :sad:.
        A lining between the shrubs and the cement makes sense. How about using post anchors ?
        I would try spraying the affected shrubs with epsom salts to try and assist them to recover :)
         
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        • Gail_68

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          Hi Ricki,
          Not being an expert on fencing, I asked my hubby as we have concrete posts in and I told him what happened with your plants and what mix you used...he said the lime as it's a killer to a lot of plants once in the soil.
          Apparently you can't beat Sand and cement mixed, do your holes and break some bricks and add them as a support around your posts in the hole, then add in the cement and keep hitting it with wood till it goes level to the service.
          We added Clematis climbers by our posts and they kicked off lovely besides other plants.

          Also I agree with Verdun who as given great advice :)
           
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          • clanless

            clanless Total Gardener

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            Just want to balance this out a little - lime is not always a bad guy in the garden :spinning:.

            I understand that the the difference between 'normal' and 'ericaceous' compost is that 'normal' compost contains added lime - to make it PH neutral.

            Doesn't cement contain calcium (lime) - but in a negligible amount? Leaching will probably take far longer than a month.

            I've plenty of limestone gravel in my garden - it doesn't harm any of my plants.

            We may be barking up the wrong tree blaming leached lime.

            Like the idea a packing out with bricks - to save on concrete.

            Quite happy to be corrected, if I have the wrong end of the stick here :dbgrtmb:
             
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            • Gail_68

              Gail_68 Guest

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              Your correct as my hubby said some plants need lime but it can harm a lot and he added bricks in the bottom to really stabalize them besides the concrete.

              Everyone does thinks differently and it's just a shame Ricki as lost his plants, can't soil be tested?:)
               
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              • pete

                pete Growing a bit of this and a bit of that....

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                I've put a few fence posts in over the years using concrete and never noticed any problems.
                As to the post set stuff, I've never used it, but it must contain something different to ordinary portland cement, or an additive, in order to make it set so fast.

                Last spring a new fence was erected right across the end of my allotment, they used the fast setting stuff, and I have a number of bushes of various types growing along that boundary.
                Not noticed any problems.
                 
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                • pete

                  pete Growing a bit of this and a bit of that....

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                  I tend to think epsom salts is more for magnesium deficiency, chelated iron would be better for ericaceous plants that have been exposed to lime. :smile:
                   
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                  • Jiffy

                    Jiffy The Match is on Fire

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                    I've put up 120m of post and rail fence which was behind shubs and not had a problem, some shurb were not happy but that was from me cutting some roots when digging holes

                    but don't mix sand and cement near shrubs so that you don't get the cement dust on there leaves

                    My front garden is just limestone gravel, yew tree,ash seedlings,hebe,contoneaster and evening primerose grow well
                     
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                      Last edited: Nov 21, 2017
                    • Verdun

                      Verdun Passionate gardener

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                      Epsom salts IS for magnesium deficiency but it is also a fantastic general tonic which is why I suggested it. The damage has been done to those plants and now they need a bit of a boost to recover if they can. Neither the holly nor the privet is an ericaceous plant so an expensive sequestered iron supplement would be an improvement on epsom salts in my opinion. The timing could be the saving grace here......over winter very little growth would be taking place. If this happened during the summer I think death would be quite rapid.
                      Epsom salts is certainly worth a try......a minimum of 3 or 4 sprays now and the same again in spring is how I would handle this situation
                      It is the concentration of lime that is the problem and with time and rain it should leach out, hopefully. I certainly have often seen damage caused by concrete used locally....whether for a patio or anything :sad:
                       
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                      • ricky101

                        ricky101 Total Gardener

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                        Hi all,

                        Thanks for the big response, seems it may be the post mix thats the culprit, possibly the lime or even the heat it generates when the water starts acting on it, so will use a standard mix of sand, gravel, cement in future along with some bricks and the strong plastic bags I mentioned.

                        @clanless - good though they are , cannot get away with just spikes as the ground is too soft.

                        @gail-68 - only realised this summer that clematis are more lime lovers, will be adding some to mine in the new year as know the soil is neutral to slightly acid, probably been using too much home compost.

                        Out of interest for those bargain hunters, Epsom Salts , bought a 250g tub for £1.50 in Tesco the other day only to find later that PoundWorld had 1kg bags for just £2.50 - just off for a long soak in the bath with some ... good for humans as well as plants ..:biggrin:
                         
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                        • Verdun

                          Verdun Passionate gardener

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                          Yep! It is indeed good for us humans too. Enjoy your soak :)
                           
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                          • Gail_68

                            Gail_68 Guest

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                            Hi Ricki,
                            Yes clematis are ok mate and I added this pic last night on the clematis site, how mine took off quickly.

                            Clematis.jpg

                            Epsom salts is good for our body and makes it smooth but I turned to sea salt and I found that even better :)
                             
                          • Sandy Ground

                            Sandy Ground Total Gardener

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                            Only just seen this thread, so my input.

                            When I am using concrete for posts, I do it in one of two ways, depending on where the fence is. My first choice would be to use some of these ready made plinths...

                            plinth.jpg

                            ...They come in quite a few different sizes, and work really well. The second way would be to use these "casting tubes." ...

                            gjutrör2.jpg

                            They come in a wide range of sizes, and do work well. They can also be used for other purposes in the garden, such as making circular stepping stones. They will reduce leaching, but not stop it completely. That can rarely be achieved when mixing concrete in situ.
                             
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                            • Ned

                              Ned Evaporated

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                              Ha! Just had a delivery of 10kg Epsom Salts for £10.40 -free delivery from eBay :yes:
                               
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