PLANT OF THE WEEK #52: Ceratostigma plumbaginoides

In the interests of fortifying the intention of this Plant of the Week blog to avoid being an impartation of expertise, and to instead facilitate the gathering of reader’s insights and experience, I’m diving into a piece on a plant about which I can speak with little confidence.

The plant is Ceratostigma plumbaginoides.  It’s one of those that’s so easy that you don’t bother to learn anything about it.  You shove it in.  It grows.  End of story, and enquiry.

Ceratostigma in context – the red thing in the centre of the image

Into that mix, add my ongoing confusion about the difference between C. plumbaginoides and C. willmotianum – the two most commonly available species here.  I don’t know how many times I’ve looked up the difference between them, and had them sorted, only to have to go through the same process when next I wanted to use or refer to them.  They’re like twins to whom you’re introduced at the same time, so that you know both of their names, but can’t quite recall which name pertains to which twin, so you avoid referring to them by name at all.

No doubt you’ll tell me if I’m wrong (and I need you to!!), but C. plumbaginoides is the decidedly low, ground-covering one, spreading my underground rhizomes.  When it dies away in winter, it leaves no woody structure, unlike its cousin.  The oval leaves are nice enough, and very, very late to emerge (which is just as well, since they can be burnt by late frosts), making it – at least theoretically – a great plant to grow over the top of bulbs, which would be dying away by the time it kicked into growth.  

The Ceratostigma/ivy mix under Italian cypresses in Verona

But you don’t know you want it until the first magically gentian-blue flowers emerge in mid to late summer, surrounded by red bracts, which provides the otherwise cool colouring with a lovely ember-glowing warmth.  From then, it just keeps getting better, flowering more heavily as the season progresses, as if it’s aware of its impending doom and is in a hurry to get the job done.  Then, in those last few weeks, the sky blue of the flowers is thrown into relief against a ruby-red background of autumn-toned foliage.

Any confidence I have about the kind of conditions that it likes best (always, in my assumption, full sun) were rattled about eight years ago when I saw it in apparent full shade, in the powder dry and root-ridden soil beneath old Italian cypresses in the Giardino Giusti, Verona, Italy.  It was growing amongst ivy, and was just popping up here and there, as if it was the ivy that was in bloom.   It was far and away the best use of it I’ve ever seen.  I can’t imagine how it coped with both the shade and the competition from the ivy, and can only assume that the ivy is cut down to the ground on an annual basis, in order to allow the Ceratostigma a head start, but I don’t know.

Again at Giardino Giusti, Verona. I’m baffled as to how it survived the competition with the ivy, and the tree roots.

But certainly, in root-ridden soils beneath evergreen trees would be about the last place I’d think of growing it.  But it worked brilliantly.  

Humbled again and again.

Where have you grown Ceratostigma plumbaginoides? And has it surprised you with its tolerances?

Discussion

  1. I have grown plumbago in shade and light shade. In heavier shade it grew very well in the shade location intermixed with ferns and bleeding hearts where soil was average ,but didn’t dry out to severely in summer heat. The other shade area where it didn’t thrive as well was under shade of a maple tree above a stone retainer wall which would dry out extremely in summer months. I think it would probably grow ok in full sun,but the foliage would not stay as lustrous during a hot dry summer. My newest garden I just planted it a year ago. This location is my favorite for this lovely groundcover. This location has light shade,no summer heat stress,and doesn’t get extremely dry late summer. It is thriving and spreading throughout this area in combination with hostas,ferns,and gaultheria. I agree that it would go nicely with spring bulbs being it doesn’t awaken from the soil very early in the spring. Super groundcover for its late season blooms and wonderful fall color leaf fascicles and leaves.

    1. Where do you garden, Larry?

    2. I garden in NorthEast USA near Philadelphia.

  2. I saw it growing unassisted in a vacant block in Bendigo’s lovely View St – I still marvel at the sighting to this day. Tough customer!

  3. Wow. I am so impressed that this plant likes shade. I have only seen it in full sun where it goes through a bit of a ratty period. I have just managed to acquire a plant and have it in full sun where so far it looks good but the sloping site does send some moisture to it. I just love the pure blue of the flowers with the changing foliage. Despite rarely being seen in our nurseries here in the West I believe it to be very garden worthy in our changing climate

    1. I too am impressed, but a bit unnerved by not understanding when and under what conditions it will perform this well in shade… Will be very interested to hear what how it performs for you in part or full shade

  4. Last year, around about this time, I posted a photo of cerastigma on Instagram. It was looking its autumnal, beautiful best-rich crimson/red, with a hint of equally rich brown. In my accompanying post, I aired my cerastigma summer frustrations. It gets chewed, it sulks on hot days, Its leaves fail to do justice to its blue flowers. It’s marked for removal. Then autumn comes, and all is forgiven. I’ve moved it around my garden and agree with others that it is summer-happier away from direct, hot sunlight. I’ve taken up your suggestion, Michael, to plant it under trees in company with vinca minor. It’s surviving reasonably well, especially where the sprinkler sometimes passes over it. As others have noted, maybe it needs companions to feel loved.

  5. I love this plant, and have several clumps of it in my garden. Mine do fabulously well in full sun or a little shade. I have one in quite a shady spot and it died. So I replaced it with another one that also died. So my theory was that it really disliked the shade, but you have all proved me wrong there!!

Leave a Comment

More Blog Posts

The life and times of Sedum ruprechtii

I’ve never had any problem remembering the name of this fabulous sedum.  I can’t, even if I wanted to, shake the lingering images of Steve Martin playing Prince Ruprecht in Dirty Rotten Scoundrel ...

PLANT OF THE WEEK #12: Bupleurum fruticosum

In my previous contribution to Plant of the Week, I wrote about Pachystegia insignis, the Marlborough rock daisy. I opined the fact that, although it is a first class garden plant, it is a rather unat ...

PLANT OF THE WEEK #13: Miscanthus transmorrisonensis

Yep, it’s a bit of a mouthful of a name, but it’s very satisfying (and invariably impressive) to say once you’ve nailed it. In singing the praises of Miscanthus transmorrisonensis, it’s necess ...