By Gmachetts
United Kingdom 
How and when can I split my large clump of arum lillies? They have been in same spot for about 8 years and have got rather large! Masses of flowers this year
5 Aug, 2015
Answers
Oo how lovely ! Dont destroy it.
5 Aug, 2015
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Depends what you mean by Arum lily - I'll assume you mean Zantedeschia, and as its in the garden, probably the variety 'Crowborough', rather than Arum italica or similar.
You can split the clump but it should be done in spring, just as growth begins, rather than now. Here's a link to the RHS for more information
https://www.rhs.org.uk/advice/profile?PID=177
5 Aug, 2015