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Dividing spiraea japonica

JoeXJoeX Posts: 1,783
in Tools and techniques
Hi all,

Im trying to unearth and split this mature shrub but it’s really difficult.  I’m doing more damage to the roots than I’m actually uncovering.



Im considering going in with a saw to cut the main bit in half while it’s still as is.  The idea being it will be easier to lift half of the plant than all of it.

If not, how much root damage is too much?  I can spend another half hour trying to scrape it free but you can see I’ve already damaged some roots...

Cheers TP

Posts

  • punkdocpunkdoc Posts: 15,039
    I think you will end up killing it.
    If you really want to try dividing it, early Spring would be the time.
    How can you lie there and think of England
    When you don't even know who's in the team

    S.Yorkshire/Derbyshire border
  • Lizzie27Lizzie27 Posts: 12,494
    It would be better to dig a trench all round it, at least 1 metre from the main stem if poss, then carefully digging underneath with a hand trowel to loosen the soil, before seeing if you can then dig the main part out.  If you then want to replant it elsewhere, give it a good soak, dig the new hole, soak that well and scatter some FB&B in the hole before replanting.  Is it worth the bother though?  It looks a fairly old shrub, past it's best and a new spiraea would establish much better.
    North East Somerset - Clay soil over limestone
  • JoeXJoeX Posts: 1,783
    Lizzie27 said:
    It would be better to dig a trench all round it, at least 1 metre from the main stem if poss, then carefully digging underneath with a hand trowel to loosen the soil, before seeing if you can then dig the main part out.  If you then want to replant it elsewhere, give it a good soak, dig the new hole, soak that well and scatter some FB&B in the hole before replanting.  Is it worth the bother though?  It looks a fairly old shrub, past it's best and a new spiraea would establish much better.
    Worth the bother?  Money, good gardening is why I suppose.

    I can’t dig a meter around because the soil is too shallow - I hit brick work a few inches down.  I suspect it’s roots have sneaked ways around and under that could be why it’s so hard to unearth.

    I’ve waited to divide it since I heard of such a thing nine months ago...but maybe it’s the wrong thing for his shrub.  I have this fantasy of replicating the plants that work in this garden through propagation rather than purchasing.
  • plant pauperplant pauper Posts: 6,904
    https://homeguides.sfgate.com/spirea-propagation-75615.html

  • JoeXJoeX Posts: 1,783
    plant pauper said:
    https://homeguides.sfgate.com/spirea-propagation-75615.html

    Indeed - but I was hoping to fast forward things by dividing.  I expect it’ll take years for a twig to become a metre tall bush.

    I suppose I’m being a little overly thrifty if you can get three spiraea for £12 (that’s two pints of lager in the City).

    https://www.jparkers.co.uk/spiraea-japonica-goldflame-0002106c?msclkid=162879dae5561315b6d122576bc1bd5d&utm_source=bing&utm_medium=cpc&utm_campaign=Shopping%20-%20All%20Products&utm_term=4578091544915809&utm_content=All%20Products

    If the jparkers plants are 20cm tall in 9cm pots, is that about one year ahead of a softwood cutting?
  • Lizzie27Lizzie27 Posts: 12,494
    Probably, but you'd be better off buying just one larger plant elsewhere as it would look good far sooner.  What I should previously said is that you can't divide shrubs (like the spiraea) at all as they have a woody central stem. They are not like perennials which have multiple shoots from a roundish root ball. Apologies all round. You could try pruning the spiraea quite hard if you wanted to invigorate it and reduce the size however.  The only other method of increasing woody plant might be to try to layer a pliable branch which is close to the ground - look up the process on GW website or RHS.
    The layered bit should eventually make roots and after a year or so can be cut off the main branch but it's a slow process.   
    North East Somerset - Clay soil over limestone
  • JennyJJennyJ Posts: 10,576
    Our local supermarket has small plants of Spirea "Goldflame" at £2 today.  At that price it's hardly worth the effort of taking cuttings.
    Doncaster, South Yorkshire. Soil type: sandy, well-drained
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