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Plants needing alkaline soil

LiriodendronLiriodendron Posts: 8,328
Are there any plants which actively NEED alkaline soil?  I was led to think about this by a post a couple of weeks ago which described some plants as "acid haters".  

Having gardened on alkaline, acid and neutral soils, I doubt if such plants exist.  Clearly there are plants which can't thrive in alkaline soils, but in my last garden (max pH of 6) I grew numerous things which are said to prefer alkaline conditions (like lilac, dianthus and lavender) with no bother.

I suspect that what these plants wouldn't like is poor drainage and wet winters, conditions often associated with acid soils, rather than the lack of lime.

Am I wrong?  Do you have any examples of "acid hating" plants?
Since 2019 I've lived in east Clare, in the west of Ireland.
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  • LoxleyLoxley Posts: 5,698
    I think such plants exist (the term is 'calcicole') but they are going to vary in how tolerant they are. Maybe a pH lower than 6 would have posed a problem for some of your plants. I think some plants associated with chalky soil make that their niche because it removes competition from plants that are not adapted to chalk. If you walk through the Peak District you can see how the limestone soil supports much more diverse flora than the more rank vegetation on neutral soil, or the denuded vegetation on very acid soil.
    "What is hateful to you, do not do to your neighbour". 
  • NollieNollie Posts: 7,529
    Interesting question! Plants of the brassica and cistus families are two I can think of offhand, but then that would include garden plants like lunaria, erysimum, iberis and then helianthemums, cistus, halimiums etc. I bet we will have someone with acid soil say they grow some of those perfectly well thank you!!

    Very acid soil can inhibit nutrient/mineral uptake from the soil as much as very alkaline can so it’s perhaps more where a plant sits on a scale of tolerance rather than acid/alkaline hating or loving per se.

    Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
  • FireFire Posts: 19,096
    It is a good question.

    Likewise for acid soil. Are there plants that flat out will not grow at all without heavily acid soil?
  • NollieNollie Posts: 7,529
    edited July 2021
    It’s not so much that camellias and other ‘acid lovers’ won’t grow in alkaline soil, but the calcium content of the latter prevents the plant from taking up important minerals, mainly iron and to a lesser extent magnesium and a few other trace elements. They get chlorotic. I grew a camellia in my very alkaline soil for 3 years with regular liquid feeds for acid plants plus sequestered iron. I gave up in the end, wrong plant, wrong place and put it in a pot of ericaceous compost, but it still needs acid feed (because it’s in a pot) and an occasional iron boost (because I have very alkaline well water).

    The root stock used for most of Europe’s roses is tolerant of alkaline soil, but they still need an iron boost here because of my water.

    Wild shrubs and flowers of the brassica and cistus families certainly grow abundantly around here, plus many leguminous species, which, now I recall, also like alkaline conditions. Calcicole is a term I hadn’t heard of @Loxley, but makes sense. It’s rocky, alkaline clay around here though, not chalk, but plants are similarly adapted/have made it their niche.
    Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
  • LiriodendronLiriodendron Posts: 8,328
    Yes, @Nollie - I grew Iberis, Erysimum fine in my maximum 6 pH soil... but not Cistus or Helianthemum or Halimium, because my garden (NE facing slope) got too little sun, so I don't know if they'd have grown or not. 

    @Loxley - I can see how some plants can overcome competition by occupying a niche (such as on chalk, as you say) where they will grow and others won't.  If the chalk downland is "improved" (horrible term!) by adding fertilisers they then can't compete, particularly with grasses.  But if I plant a Pulsatilla, say, in somewhat acid soil in my garden, removing competition from other plants, will it not grow?

    Wild plants will inevitably die out if they are out-competed by others more adapted to the local conditions... but does that mean they are intolerant of any other soil pH, or is there more going on than this?
    Since 2019 I've lived in east Clare, in the west of Ireland.
  • NollieNollie Posts: 7,529
    The thing is, a PH pf 6 is not very acidic, just slightly.. the lower the PH (below 5 or conversely the higher, like mine, which is around 9) the more hostile the growing environment for most plants and the the more difficult nutrient uptake becomes. Some plants are just more sensitive to the extremes than others, that’s what I was meaning about a scale of tolerance. No plant actively ‘hates’ either acid or alkaline, they just need you to directly feed them the minerals they cannot extract from the soil to thrive, hence better (cheaper, less faff, healthier plants) to grow plants tolerant of your PH range than those that aren’t. 

    But with plant growth there is inevitably more going on than just PH and nutrient availability - soil type, drainage, exposure, sun levels… all the usual considerations when choosing plants for your particular conditions.
    Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
  • ObelixxObelixx Posts: 30,090
    As @Nollie says much depends on how deep, rich and fertile is the soil.  I have always understood that brassicas, clematis, lavenders and dianthus need alkaline soil but once you add in things like a clay or loam alkaline soil with richer fertility and moisture retention things change.

    This page on the RHS website is informative - https://www.rhs.org.uk/Advice/profile?PID=763

    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
  • FireFire Posts: 19,096
    Obelixx said:
    As @Nollie says much depends on how deep, rich and fertile is the soil.  I have always understood that brassicas, clematis, lavenders and dianthus need alkaline soil.

    There's the question of 'thriving' too. My area is pretty neutral clay and camelias, acers, rosemaries, lavenders and magnolias are everywhere and seem to do well in unchanged soil. Perhaps they would do even better with ideal soil. Most people with gardens just bung things in and the plants either sink or swim.

    Perhaps it takes longer for plants to establish in dodgy soil, but once they have filled out, they learn to adapt.
  • LiriodendronLiriodendron Posts: 8,328
    @pansyface's article tells me something I didn't know - that both acid and alkaline soils lock up phosphorus.  So neutral is best for root development, presumably...

    I'm still left with the question, @Obelixx - what exactly is meant by a plant "needing" alkaline soil?  I understand about ericaceous plants not being able to access iron when planted in alkaline soils, and therefore needing neutral to acid conditions, but what actually happens to a lavender planted in acid soil?  I suspect there must be lots of micro-nutrients and trace thingummies it can't make use of as it should. 

    I'm sure you're all correct though, in saying that the physical characteristics of the soil are at least as important as the pH. 

    Thanks for helping me to think about it!  
    Since 2019 I've lived in east Clare, in the west of Ireland.
  • edhelkaedhelka Posts: 2,351
    My soil is between 5.5 and 6. Lavenders, dianthus and iberis are thriving. Lunaria, erisymum, helianthemum - ok, no problem.
    Lilac hasn't flowered for two years and that changed after I sprinkled some lime granules around. But it always has been vigorous and healthy looking.
    Brassicas are unhappy but that could be also because my soil is too loose and they need it firmer. Smaller brassicas (various salad leaves) are ok.
    I've always assumed I can't grow gypsophila... just from the name.
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