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Yearly compost change

Discussion in 'General Gardening Discussion' started by Leth, Jun 9, 2021 at 4:34 PM.

  1. Leth

    Leth Apprentice Gardener

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    Hi folks, we are relative beginners at the gardening game and I was wondering, every Spring I change the top third of our pots compost and put fresh compost in. Obviously when you have lots of pots, some quite large, this can't take lots of compost and time. Is this necessary or are we over doing it? Would feeding do the same job? In which case what is the best feed for promoting growth?
     
  2. JWK

    JWK Gardener Staff Member

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    What plants and size of pots?
     
  3. Leth

    Leth Apprentice Gardener

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    Varied sized pots from 4 inches across to three foot. Its a real mix of sizes and shapes. We also have wooden tubs ranging from four foot to 12 inches stacked in a corner. When I change the compost it means using about 5 large bags just to freshen up the top third of all my pots and tubs. The plants we have are a mix too. Various bedding plants in flower beds and Hydrangeas, Peonies,an Olive bush, Peiris, Primula, Lily, Bleeding heart, Geraniums, Fuscias and Azalea. Others I can't remember.
     
  4. ricky101

    ricky101 Total Gardener

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    Hi,

    Bit surprised you can take out a third of the depth of compost without damaging the roots ??

    Rather than digging down so much, perhaps just scrape off the top 10mm to clean things up and apply a feed, instant or slow release granules etc, and a mix of potting compost and some farmyard manure like Growsures, which we do if not moving them on to a larger size pot.

    If you are away working for long periods have a look at the controlled release fertilizers like Osmacote or if someone is around to look after them for you, something like GrowMore is good for getting things going, but once in bud/flower then typically liquid Tomato Feed is best to use, though do check on plants like Azaleas etc which need acid conditions.
     
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    • JWK

      JWK Gardener Staff Member

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      I don't have too much in containers or pots, I tend to 'pot on' some of mine that are evergreen, ie move into a slightly bigger pot.

      Some of my tender plants, that go dormant over winter, I change the compost most years and this involves taking the plant right out and removing roots so I can get fresh compost into the same size pot. You could do this with your deciduous plants whilst they are dormant every 3 years or so, such as the geraniums, fuchsia and lilies. I would use a soil based John Innes compost as this retains its structure. I am unsure about hydrangeas, olives etc as they could well dislike root disturbance and would require the 'pot on' method.
       
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      • pete

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

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        Not something I would do, removing a third of the compost on all potted plants right down to 4 ins. cant be easy and surely the smaller pots would be better potted on into bigger pots rather than do this to them.

        Admittedly once a plant gets to a certain size you have to top dress each year, and removing some of the old compost does make a better job of it.
        I which case I would add some blood fish and bone mixed with the same type of compost as the pot already contains.

        Ji type composts are better for long term pots, but add extra sand for drainage where certain plants require it.
         
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        • CarolineL

          CarolineL Total Gardener

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          I have to admit, I have lots of pots but don't bother to do anything like this! I topdress where the soil level has depleted and fibrous roots start showing, repot things in very small pots if they look as though they are getting root bound, and otherwise just feed if I remember to - normally with a seaweed feed so I don't have to worry about some of my plants that are intolerant of phosphates - though I use a cheap slow release fertiliser when I pot up most things. As @ricky101 said - if the plants are doing well, taking out a third of the compost would likely damage the roots.
           
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          • Leth

            Leth Apprentice Gardener

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            When I say the top third, its as near as possible. Obviously I can't do this for every pot and I should mention in the smaller pots we do completely change the compost and pot.
             
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