PLANT OF THE WEEK #100: Euphorbia 'Copton Ash'

One of the great ‘discoveries’ of my unwatered ‘steppe’ garden has been Euphorbia ‘Copton Ash’.

I’d admired it, from a distance, for several years.  It’s always hard to recall why you overlooked something once you no longer do, but I think it was simply the fact that until I set aside a whole zone for lower growing stuff, I never had a context, in the rough and tumble of a garden based largely on tall perennials, for something below knee height.

But after several years of internal nagging about what I was missing out on by insisting on dramatic height, I cooked up a satisfying context for the lower stuff, and the previously overlooked Euphorbia ‘Copton Ash’ immediately rose to hero status.

Euphorbia ‘Copton Ash’ peaking in December, in a garden that is never watered

Euphorbia ‘Copton Ash’ dons fine blue grey foliage that arranges itself predictably and pleasingly along unbranched stems, arising from a dense growth point, creating a dome – a virtual vegetable hedgehog, to about 40cm.  From late spring, each stem gives rise to a great froth of classic lime-green flowers whose acidity and vivacity are amplified by the contrast with the blue-green of the leaves.  

The whole structure of the plant is sufficiently loose and open to allow light through, making it the perfect companion through which other low-growing plants might puncture.  I had for many years dismissed the bulbous Triteleia laxa (probably best known by a previous name – Brodiaea ‘Queen Fabiola’) as near to useless, what with its foliage turning brown as the navy flowers emerge, leaving the flowers looking self-conscious and entirely unsupported, until I hit on the combination with Euphorbia ‘Copton Ash’.  The foliage of the bulb has access to light as the dome of euphorbia foliage expands, only being engulfed as it starts to die off.  As the euphorbia becomes a little more open and lax with the onset of flowering, the stems settle around those of the triteleia, supporting them both visually and physically, and providing them with the perfect complementary colour. 

I’ve since introduced Verbena rigida to this part of the garden, and this has spread with a little more (only a very little more) vigour than I’m entirely comfortable with, and likewise punctures through the euphorbia.  But having such slender foliage of its own, it provides no competition for light so doesn’t undermine the euphorbia in any way.  The consequent purple/lime combination is rather more brash than the navy/lime combination elsewhere, but I’m not afraid of a bit of brashness.

While the Lambley nursery catalogue suggests that Euphorbia ‘Copton Ash’ produces a succession of blooms over a long period, I find that in my setting (perhaps due to absolutely no irrigation) the flowers are mostly produced in a pre-Christmas flush, and that they’re just exceptionally long lasting, rather than continuously produced.  In fact, they’ll last right through the summer, and into the autumn, fading somewhat, but never entirely losing that rare charm of lime-green over blue-green.  I don’t usually find any reason to dead-head them until well into winter.

Euphorbia ‘Copton Ash’ amongst colchicums, at the end of the very dry summer/autumn of 2019 – looking faded and threadbare, but still making a contribution

While it’s firmly evergreen, Euphorbia ‘Copton Ash’ is at its least appealing, for me, in winter.  I expect that’s largely due to the hostile and long-lasting low temperatures around here, and the corresponding rainfall over soil that’s probably not quite well-drained enough to keep them partying year ‘round.  In better conditions, they’d provide a really worthwhile ‘bun’ of young leaves right the winter through.

Like lots of evergreen euphorbias, my plants of Euphorbia ‘Copton Ash’ are starting to look a bit past their best at six-or-so years of age.  But with all the work they’ve done, and joy they’ve given, I’ll gratefully ‘retire’ this first generation, and get on with a replant.

Euphorbia ‘Copton Ash’ in the quarry at Stone Hill

Please note: If your page states that comments are now closed, that’s not true. You just have to sign in to your free ‘The Gardenist’ account to be able to comment (and btw, we’d really love you to comment!)


  1. It is a great plant Michael but it’s your use of the massed Colchicums here that I always find attention grabbing. An orgininal idea or where have you seen that done before?

    1. I guess it is kind of original. I don’t know that I’d ever seen a convincing use of colchicums in the past. They mostly just appeared in what were otherwise bare patches at the front of a border in autumn – to me the least appealing context. The pic shows them spangling right through an otherwise low, relatively sparse planting with a gravel mulch – the key being to not be aware of them being there when there’s neither foliage nor flowers showing.

  2. Hi Michael,
    I have also been admiring ‘Copton ash’ at a distance and really wondering why now, it looks so great in these photos.
    Thank you for this and congratulations on 100 plants of the week. Each post is so informative and helpful. Your newsletters and blog posts are so helpful in general as I think your climate is similar to the upper Blue Mountains where my garden is. Which leads me to why I follow a whole lot of gardens/gardeners in the UK and Europe on Instagram yet have total FOMO for the most part of Winter – something has to be done!
    Ps. Yes I am sick of this weather too!
    Enjoy some time away.
    Thanks again. Leila

    1. Thanks Leila, Really appreciate the affirmation. I’m back now, all dosed up on sunshine!

  3. oh you make everything look so easy! All my knowledge I’m gaining at the moment is coming from one source – I’ll have people pointing and saying ‘Oh look, it’s a Michael McCoy’ as they do their morning walk. I’m sure some of me find it’s way into the soil, but your writing really does inspire, so thanks for being so generous.

    1. Thanks so much Julia. Making it look easy is a serious fault. Cos it’s so not. Any apparent simplicity is on the other side of a whole lot of failure. But I love that gardening stretches my intellectual, physical and philosophical capabilities to the limit. I’d be bored with it otherwise.

Leave a Comment

More Blog Posts

Up or out?

Seems like some climbers are happier when they’re going up, and others when they’re going out.  The wisteria I kept going on about back in early summer absolutely rocketed up its wire, but lost i ...

Thinking inside the sphere

Just clipping my English box given the cool and cloudy weather, thus minimizing the post-clip burn that can decimate these otherwise bullet-proof plants.  Box manifests in three forms here – sphere ...

Of timelessness and moment

One of the unsung aspects of gardens is their super-ability to have one foot in timelessness and the other in the current moment. In a French garden, for instance, or an English garden, it’s possibl ...