This flowers best in sunshine, despite the books saying that is is a good plant for shade! Put it in a sunny spot and let it get a bit bigger. Only cut it back at the end of summer, it will die back to nothing but re-emerge in springtime.

I found your question very interesting. We dug up a root of Acanthus in the UK and put it in our garden in a slightly shady position and it never properly flowered. When we came to France, there was an acanthus growing by the wall of the house, which however much we hacked back kept returning! We planted part of it in a west facing flowerbed and after about three years it suddenly rewarded us with numerous spikes of beautiful flowers. Ever since it has flowered every year. I guess this is just a very sulky plant which takes its time and wants really good conditions. We never cut ours back but it dies down as Volunteer describes.

When we want flowers on ours, we plant them where they get morning sun, though that burns the leaves somewhat in late spring. They are very shy to bloom in complete shade, even here in the desert.

Thanks to all who replied to my acanthus question.