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trouble with acanthus

Does anyone have any bright ideas?  About four or five years ago I planted some Acanthus mollis in a nice spot, gets morning sun.  It did really well for a couple of years with lovely flowers, but then we went away overseas.  Last year when I first returned I had not a single flower spike, and even the leaves weren't as spectacular as they might have been.  As my tenants didnt really look after the garden I assumed some TLC and feeding might help this year, but again there's nothing. 

I think I have two options - either to leave them for another year and just NOT feed and see if they do better with some harsh treatment, or I can move them to the back of the garden, under an apple tree, an area I am trying to develop with a lot of white flowers so that it forms a focal point at the slightly shadier end of the garden.  My instinct is to move them as the spot they are in now is one of my 'good' spots and there are all sorts of other things I could happily plant there.  I know they might reappear again if I move them but I figure I can keep digging up.  Or use the dreaded Roundwood Gel!  Does anyone have any advice/thoughts/suggestions?  Thanks 



  • nutcutletnutcutlet Posts: 27,411

    I have had Acanthus mollis for 12 years or more. This year it's going to be brilliant for only the 2nd or 3rd time in all those years.

    I threatened it last year, all mildewed leaves and no flowers. It must have listened. I would cut back on the TLC, especially any involving nitrogen.

    It's hard to move, you get  acanthus in both sites

    In the sticks near Peterborough
  • WintersongWintersong Posts: 2,436


    This is one of three Acanthus Mollis I grow. Firstly, its huge and I only fed it once in its lifetime last year, because it was looking less than vigorous. The leaves were yellowing and it was reluctant to flower. Saying that, it is over 15yrs old and I can't remmeber a single year it hasn't flowered. I never planted in any kind of special soil since back in those days, everything went into my sandy builder's rubble soil whether they liked it or not.image

    Secondly, It's at the front corner of my first border near the house. I have never regretted planting it there although this year, its over extended itself and will get a bit of a prune at some point. It's architectually splendid with so much to offer the eye and to be honest, the only problem it has is midday sun. They tend to sink a bit in terrific heat but perk up again by late afternoon.Perhaps, yours is in too much shade? It's got to be a reasonable amount of sun I've read.

    Thirdly, be warned! These things are invasive if you are not a clean freak like me. The massive flower spires will drop large seeds close to the plant that form baby plants and is hard to dig our since each tiny bit of root will form an entiirely new plant! Cut off any flower spikes in the autumn, or be diligent at the plant base come early spring. I failed to do the hoovering properly this spring and my plant grew wider as a result.

    I think these add majesty to the garden, but each to their ownimage

  • bekkie hughesbekkie hughes Posts: 5,294
    Mine took a few years to flower, it was well worth the wait. It seems to like it in a reasonably heavy soil, in a border which looses the sun around midday image
  • adamadamantadamadamant Posts: 272

    Thank you for your comments.  I would have replied sooner but didn't get any email alerts so it was a while till I realised there were responses. I think I'm going to get rid of it completely - my garden isn't large enough to give up the space to it if it is unreliable, and quite evidently moving it is going to be problematic so I may as well deal with it in only one area.  Shame, but I am grateful for the thoughts.  

  • Janie4Janie4 Posts: 15

    I finally gave up on my acanthus. In 10 years we only got flower spikes twice, and it struggles to look well. Our soil is rich heavy clay. 

    So last August I took it out. It wasn't funny - roots going 2 foot deep and 4 feet in every direction. I emptied the flower bed and dug through the whole lot very carefully removing every little piece. Of course there have been a few new sprouts but I am removing them as I see them (every 5 days or so) and digging deep for their source.

    So we got back from holidays to find a 'hedge' of acanthus across the whole bed.

    What now? Any ideas?

    So I agree, be very careful with this plant. It is seriously invasive even if it looks like it is struggling to be happy in its spot.

  • wildaboutwildabout Posts: 6

    I was given 3 of these plants when I first moved into my house with a rubbish tip of a garden, just to fill the borders with something whilst I decided on what I wanted to do.  I just 'bunged' them in and left them to it, in really rock hard, poor soil, in full sun and have never watered them, let alone fed them!  Result? Massive plants with so much leaf and flowers. Have had to cut off a lot of the leaves as they are covering so much ground and I will probably have to move them as they are definitely taking over!!

  • bekkie hughesbekkie hughes Posts: 5,294
    I have to say, once they actually decide to get going, they really do get big, any bits of root also take and flower, just one of those oddball plants i think! image
  • bekkie hughesbekkie hughes Posts: 5,294
    Janie, it looks like you are stuck with it, i dont do chemicals, but maybe thats your option if you really dont want them, sorry
  • FleurisaFleurisa Posts: 779

    Have you tried feeding it with a high potash feed

  • Janie4Janie4 Posts: 15

    Bekkie, no I don't do chemicals either. It is getting tempting though.

    Fleurisa, do you mean feed it to get rid of it? or are you aiming to make it flower? At this stage I want it to go away and give me my flower bed back. I still have some lovely perennials waiting to go back in, a whole season gone!

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