Plant Profile: Acanthus Polystachyus....or is it!? A shrubby form with INCREDIBLE magenta flowers!!!

This week on The Horti-Culturalists we look at ONE of Stephen Ryan's national collection of plants: the Acanthus. And particularly his amazing shrubby magenta flowering form called Acanthus polystachyus...or is it Acanthus montanus....or even Acanthus pubescens!!?? Perhaps you can help us! Do comment below if you grow this amazing plant and know for sure what it's called! We also talk coffee grounds as mulch!
Acanthus polystachyus (we'll stick with this name!) is a sun loving, frost tender, drought tolerant shrub growing to 3m , or 10ft, with the most amazing spikes of magenta blooms late summer early autumn and striking foliage. In fact you could grow it for the sculptural foliage alone.
The plant collection organization Stephen is president of is:
https://www.planttrust.org.au/
A similar organization in The UK is:
https://www.plantheritage.org.uk/
If you know of a similar US organization, or anywhere else, do let us know!
The video we refer to about coppicing a Catalpa is here:
   • Coppicing a Golden Indian Bean tree to max...  

0:00 introduction
0:25 Plant Trust of Australia
1:00 coffee grounds as mulch
2:04 shrubby forms of Acanthus
2:25 the national collection of Acanthus
3:37 Plant Heritage UK
4:19 herbaceous perennial Mediterranean Acanthus
4:39 flowers
4:56 natural range
5:15 growth habit
6:24 ideal growing conditions
7:10 foliage
8:36 availability
9:26 there's some confusion about the name!