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Renewal of large planters at the seaside

jandlspicerjandlspicer Posts: 5
in Problem solving
Hello, We are replacing and repotting some large (750 litre) planters in a courtyard of a seaside block of flats containing mature cordelines,  and phormiums. What soil/compost do we need? John Innes 2 seems very expensive. We covered the original multi-purpose compost with pebbles in the old planters to stop it drying out, or blowing away! Are there any other sturdy plants that you recommend to share the bed? 

Posts

  • FairygirlFairygirl Posts: 55,117
    edited August 2021
    I'd just get a load of ordinary topsoil and mix some cheap pea gravel into it, and you wouldn't need to replace all the existing soil. Compost is no use, even for those plants. It just breaks down over time into nothing, although you can mix some into the general mix. That's what mine grow in  :)
    I doubt there would be room to add anything else into the containers, unless you only have one plant in each? Those plants get very large - especially the Phormiums, because they have a different growing habit to Cordylines, and spread across rather than having a single trunk.
    You could maybe add some small spring bulbs to the base of the Cordylines.  Crocus or Muscari would be ideal as they're quite tolerant of different conditions.  It's a good time to buy bulbs as they're available around now. Online suppliers are better than Garden Centres as you can buy in bulk. 
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • jandlspicerjandlspicer Posts: 5
    That's very helpful, thanks. We shall need to find some soil in bags (we live on the roof). We are putting some polystyrene in the bottom to aid the drainage and the weight of the planters. There are some agapanthus too to transplant that seem to have done well. What do you think?
  • FairygirlFairygirl Posts: 55,117
    Yes - those might work.  :)
    I didn't realise you were on a roof. That certainly makes a difference!
    Yes - it's a good use for polystyrene. I've done that for large pots which are heavy, especially if the plants going in them don't need the complete depth of the pot in soil.
     
    What are the dimensions of the planters? I'm struggling to work out what 750 litres would be, but it's certainly a lot of average bags of soil/compost. 
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • jandlspicerjandlspicer Posts: 5
    That's good! We will have 4 planters. Each one is 2 metres long by 60 cm wide and four planks of decking tall, almost 60 cm so 0.6x0.6x2, that's 0.72 metres so 720 litres each. Yes a lot of soil to carry up the stairs!

  • Lizzie27Lizzie27 Posts: 12,494
    Have you checked the regulations at your block of flats concerning weight load on roofs?  Seems to me the planters will be extremely heavy filled with soil. Better to be safe than sorry! 
    North East Somerset - Clay soil over limestone
  • jandlspicerjandlspicer Posts: 5
    That's a very good point. The present planters are bigger though (slightly) and 15 years old so the replacements should be OK 1/4 filled with polystyrene - depends I suppose how much heavier soil is than compost. Probably not much heavier than (wet) compost?
  • FairygirlFairygirl Posts: 55,117
    @Lizzie27 - the OP has already mentioned putting polystyrene in the base to negate the weight, but it's always a factor  :)
    Yes - they're quite a good size, so it gives you plenty of scope. I think it comes down to whether you want one of the Cordylines or Phormiums as a central plant with others next to , or alongside , them. That would certainly be the best solution. You couldn't really have a row of Cordylines due to the growing habit.
    The Agapanthus would work well each side of a Phormium, and they would also work with spring bulbs and hardy geraniums for example. All of those would cope with an open windy site too, although the Agapanthus might need some support. Some are hardier than others though, so you'd need to check that. 
    Take a look at some of the ornamental grasses and perennials that work with them. We had a query on the forum earlier about what to put in some planters beside a patio. I put a link and some suggestions on that. 

    https://forum.gardenersworld.com/discussion/1058771/planters-advice#latest
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • jandlspicerjandlspicer Posts: 5
    Very helpful link. We do have some hardy trachycampus that have thrived, though some varieties seem to be less vulnerable to windburn than others.
  • Nanny BeachNanny Beach Posts: 8,719
    We are 10 minutes from the sea,plus get wind from the south downs,russian sage,and nepeta,are happy, Pittosporum.(we have them in planters)erygiums.cordylines.unless you are very sheltered,go for the shorter grasses,we didn't they are difficult to support and snap off
  • Butterfly66Butterfly66 Posts: 970
    I believe you can get specific planting mediums/lightweight soil mixes which are designed for roof gardens. It will include expanded clay which help with the wight and water retention so you get a compost which behaves more like natural soil without less weight.
     If you have a garden and a library, you have everything you need.”—Marcus Tullius Cicero
    East facing, top of a hill clay-loam, cultivated for centuries (7 years by me). Birmingham
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