Sacha wrote:

But no, it's not a very exciting Euphorbia, given all the
others we can and do grow! I quite like its greenness but I don't like its
invasiveness.

I rather like it, especially in its early phases when it appears as a
40-60 cms. high stem with its leaves arranged in opposite pairs;
criss-cross fashion. In others' gardens mind you, not mine! It loses
the plot once flowering is under way and if you want a few seeding
themselves about, you have to turn a very blind eye as it declines.

When I first came here, such soil as there was consisted of a thin
scrape of dust, lumps of ancient mortar and stones overlying mudstone.
All that grew were Valerian, Caper Spurge and a few clumps of Sedum
dendroideum 'Prealtum' (a shrubby succulent from Mexico that is an
'escaped' pot plant in coastal regions of S. Devon). The spurge
disappeared immediately soil conditions were improved and made more
acidic - unable to compete with more lush and interesting stuff. It
seems to do best where the soil is dry and somewhat alkaline, but is
easily hoed out if you don't want it.

As to its alleged mole-repellant qualities, my experience is that it
simply does not work. My parent's old garden near Stourbridge was
plagued with moles and Caper Spurge was introduced as a last-ditch
attempt before adopting much sterner methods of control. It was a
complete failure and I swear that mole activity was increased close to
where the spurges were planted.