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Planting clusters of the same perennials densely spaced


I'm planting a new garden and have ended up with about twice as many of some plants than I needed.  [I bought these from a wholesaler which had minimum order of 24 of each plant, which was still much cheaper than the number I needed from other nurseries].

For the following plants, if I am making small clusters, would it work to put them more closer together?  For example a cluster/drift of six plants each 25cm apart vs three plants each 35cm apart (twice the density).  They are all small, in 9cm pots.

1 - Actaea ramosa 'Pink Spike' 
2 - Allium 'Millennium' 
3 - Aster frikartii 'Mönch'
4 - Salvia nemorosa 'Caradonna'
5 - Sedum 'Matrona'
6 - Stachys monieri 'Hummelo'

I'm aiming for a dense planting, but there is probably a limit!  Otherwise I can give the extras away.



  • newbie77newbie77 Posts: 1,719
    I don't have experience with all of your plants except salvia Caradonna. That salvia would be ok to plant densely as it more of an upright type of plant. You can always thin out some of its plants if it doesn't look right next year. 
    South West London
  • JennyJJennyJ Posts: 8,804
    Yes, go for it and thin out next year or the year after if it gets too crowded. Textbook advice is to plant in groups of odd numbers so you might want to try 5s and 7s. You could try irregular shaped groups or drifts for a more naturalistic effect.
    Doncaster, South Yorkshire. Soil type: sandy, well-drained
  • That would work. I second the odd numbers thing--heaven knows why this makes a difference, but it does.

    If you have spares after that, how about neighbours? Mine are always very glad to have my unwanted plants and divisions.
  • LG_LG_ Posts: 4,107
    You'd be going with the current 'done thing' in planting design - dense planting with 9cm pots, then later editing as necessary. It has its advocates and its detractors, but I would definitely go for it in your situation.
    'If you have a garden and a library, you have everything you need.'
    - Cicero
  • SophieKSophieK Posts: 242
    edited April 2021
    I tend to plant densely as the aim is to be overwhelmed with plants and not to see soil. It looks great but makes for delicate treading if you need to attend to a plant at the back. For example, I planted cosmos and zinnia seedlings out quite close so they should support each other (fingers crossed. And yes, before anyone says it's very early but 1. I have a very protected sun trap of a garden, night temps are okay here now and 2. I have spares in the cold frame)

    Like others GWers I would advise to plant in clusters of odd numbers (that works also for interior design / styling - it's just more pleasing) and repeating them. So five of of this and that and the other and repeat.

    However, be mindful what plants you put next to the other as the ones you have chosen do not have the same sun/light and water requirements.

    And if you have spare I am sure a keen gardening friend, relative or neighbour would be delighted to get you surplus. I wish I lived near you ;) 
  • What a lot of effort has gone into your border prep. I fi were a plant I'd be itching to get my feet in there.

    I agree with the others, you can opt for dense planting knowing you will can split and move in the long run. Some things will bulk up more than others. I grow all those plants except the actaea. I struggle with Stachys 'Hummelo' - it doesn't seem to like my garden.

    Most of my herbaceous went in as 9cm and by the end of the summer you won't be able to tell the difference between them and a 2L plant. 

    Do post some pics as your garden develops.
  • FairygirlFairygirl Posts: 52,045
    A note of caution - if the conditions suit Salvias and Alliums, they won't suit Acteas.
    Acteas need soil that doesn't dry out [the wetter the better] and shade, to do well. 

    If you still want to plant those, you could create a wetter area by using a plastic lining, lots of holes in the bottom, and a layer of gravel. Some heftier soil added will help retain moisture  :)
    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • curious_monkcurious_monk Posts: 9
    edited April 2021
    Thanks Fairygirl - the garden is south facing and the Actaeas will be down the back by the north facing wall (along with ferns, hostas, hakonechloa macra, etc).  So down there it is shady and fairly damp all the time.  The other plants will be both south and east facing and get lots of sun.  I dug in lots of compost (I think 4 cubic meters) about 6 months ago so hopefully the soil is moisture retaining - I have noticed it is now full of big worms.  So hopefully that will all work! 
  • curious_monkcurious_monk Posts: 9
    edited April 2021
    What a lot of effort has gone into your border prep. I fi were a plant I'd be itching to get my feet in there.
    Thanks!  Yes, has been a bit of a marathon, starting with removing about five cubic meters of builders rubble.  The cedar slat fence on the right and the hole for the inground trampoline were projects that took me a good few days too!  :smile:   Some plants have arrived already with the rest of them arriving next week, so can't wait to get planting!!

    And re your Stachys 'Hummelo' does it just not flower well or does the foliage have problems too?  Pictures I've seen online looks like it has attractive foliage...

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