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Acidifying soil

WiltshireWildWiltshireWild Posts: 64
edited June 2023 in Problem solving
I have just planted Hydrangea Annabelle in my Ph7.5 limestone soil here in wiltshire. Although I have not yet seen how the plant will react to the unfavourable alkalinity I am exploring the idea of soil acidification. My main question is, does using iron sulphate actually acidify the soil or does it just have only a short lived affect acidifying perhaps only the water suspended within the soil. Its hard to imagine you can actually acidify limestone soil. 
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  • WaysideWayside Posts: 845
    No expert, but as I am chalk I did look into this, and from what I remember it's easier going from acid to alkaline than the other way around, and it's a long arduous process, if you really can be bothered.

    I am going to be moving to bokashi composting soon as my bins were ratted.  And I read that that can acidify a little bit.  But whether that would make a blind bit of difference in our chalk garden I very much doubt.
  • WaysideWayside Posts: 845
    Having said that my uncle is on chalk, and his garden once was a market garden.  And has some very impressive azaleas that seem quite happy.  Are you on the wiltshire chalk downs?

    Reading the RHS page https://www.rhs.org.uk/soil-composts-mulches/acidifying-soil suggests that if you have free chalk in the soil you won't get far.  So perhaps better off building up new medium in a patch.
  • Pete.8Pete.8 Posts: 11,340
    edited June 2023
    This article may shed some light-
    https://www.plantingtree.com/blogs/gardening/how-to-change-hydrangea-color

    Ps - that said, Annabelle is White I believe, so I don't think it'll make any difference if your soil is acid or alkaline, it'll stay white - but I'm not by any means 100% sure abt that

    Billericay - Essex

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • WiltshireWildWiltshireWild Posts: 64
    Yes that does seem sensible. However that is quite a large amount of work and compost considering the spread of an established hydrangea annabelle. I have seen annabelle grow well in north wiltshire but admittedly in well tended gardens that have much higher quality soil than mine.
  • gjautosgjautos Posts: 429
    Would it not be easier to grow in a large pot in ericaceous compost?
  • bédébédé Posts: 3,095
    edited June 2023
    If your soil is pH 7.0, you will be able to move it a bit in either direction.  pH 6.5 or less and 7.5 or more, the bulk components will win.

    Best to live with what you have been given.  Of course it will vary, test and select the various best areas.

    Clay-with-Flints is a geological formation that sits on top of chalk, it results when all the chalk has been dissolved out.    If you have aeons to play with, it might be worth the wait.

    Woodlands on chalk will accumulated a low pH top soil, as acidic material accumulates.  A bit like peat formation.

    Sometimes it's just a case of topping up with a missing mineral and nothing to do with akalinity/acidity:
    Chalk added to peat to provide calcium.
    Chalk aded to brassicas.
    Chelated iron added to chalky soil.  The chelation slips the iron in by the back door.
    Alum addded to Hydrangea macrophylla or serrata soil to change the flowwr colour to blue.

     location: Surrey Hills, England, ex-woodland acidic sand.
    "Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
  • LynLyn Posts: 23,190
    Pete.8 said:
    This article may shed some light-
    https://www.plantingtree.com/blogs/gardening/how-to-change-hydrangea-color

    Ps - that said, Annabelle is White I believe, so I don't think it'll make any difference if your soil is acid or alkaline, it'll stay white - but I'm not by any means 100% sure abt that
    They all prefer to grow in acid soil,  the colour change is dependent on that, and the white will stay white,  but still needs to grow on neutral to acid.
    depends on what you want from a plant,  it will probably grow but won’t reach its full potential.
    trying to change the soil you have is never a good idea in the long run. 
    Gardening on the wild, windy west side of Dartmoor. 

  • ObelixxObelixx Posts: 30,090
    I grew lots of very happy hydrangea paniculata on deep, fertile alkaline loam in my garden in Belgium.   I moved 3 here in pots to a garden with neutral to acid loam and they're not keen, largely, I reckon, to the lack of spring and summer rain these last few years but I'm working on improving moisture retention with lots of organic matter mulched on each year.

    Trying to grow a hydrangea arborescens which likes acid to neutral soil in a very alkaline soil is not a battle you're likely to win so I suggest either planting it in a huge container filled with ercicaceous loam based soil mixed with some ericaceous MPC and then watering it only with rain water and feeding it every spring or finding it a good home with someone who can give it what it needs and planting something more suited to your garden conditions.   
    Vendée - 20kms from Atlantic coast.
    "The price good men (and women) pay for indifference to public affairs is to be ruled by evil men (and women)."
    Plato
  • WiltshireWildWiltshireWild Posts: 64
    The thing is I have seen it growing well in my area at public open gardens such as in the walled garden at Badminton House. But I do have a strong feeling they have been amending their soil for many decades. My soil is very poor quality, although I did add quite a lot of compost into the hole. 

    Would the first bad sign be chlorosis/iron deficiency?
  • WiltshireWildWiltshireWild Posts: 64
    I have a macrophyla that struggled to establish and showed signs of chlorosis, but after 6years now seems ok. 
    By the way there is definitely free lime in the soil and it fizzes when mixed with citric acid. Going by what it said on the RHS website it doesnt seem viable to fix with sulphur. 
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