Plant of the Month November 2016

Posted on 29.10.2016 |
Updated on 27.11.2018 |
Added in Plant of the Month

Strobilanthes rankanenesis

I must admit to a little hesitation over this month's choice, on two counts. First, maybe this slot should go to a truly hardy November plant that shrugs off harsh weather and still shines through, for example, one of the glowing hardy chrysanthemums now lighting up the border. And second, reliable information on this plant is hard to come by, and includes two differing descriptions, from two unimpeachable sources. However, to exclude a beautiful plant that has flowered till nearly the end of November, for the last five years, because a hard frost will cut it back, seems ungenerous. Similarly, why should it be passed over because our own knowledge is imperfect? (Anyway, POTM November 2015 will tell you quite enough about my weakness for hardy chrysanthemums).

You may well have come across Strobilanthes atropurpureus in Graham Stuart Thomas' ‘Perennial Garden Plants', where he describes it as ‘a bushy growing plant, more like a salvia than an acanthus.' I grew it some years ago, and while enjoying it for its extension of the flowering season, its demeanour was modest. So when Julian Sutton listed Strobilanthes rankanensis in his sorely missed ‘Desirable Plants' catalogue, as a spectacular 6ft dome, I had to have it. Sadly, for me it only reaches 4ft, but I do grow it in the deep shade of a walnut. I also checked it out online, to discover that it was listed by Crug Farm, intriguingly as ‘a low growing perennial to a height of 20cm, collected in Northern Taiwan'. My plant appears to have decided to split the difference! A quick look in the Plant Finder reveals 5 sources of straight S. rankanensis, with the Crug Farm variant under a separate collection number – phew.

It begins flowering in September, and carries on (and on and on) until the first stiff frost. It tolerates shade, which also protects it from frost. The hooded flowers are soft blue-purple and the silhouette is a rounded dome. The fat jammy-coloured pokers of Persicaria ‘Fat Domino' will also tolerate shade, making it a good neighbour that will flower for as long as the Strobilanthes. I'm tempted to try it in the open border, where it would sit well with deep gold Rudbeckia deamii and the indigo purple of Aster ‘Marina Wolkonsky' – if I do, maybe I'll get to see the 6ft I was hoping for.

Some Strobilanthes species seed around, but I've yet to see seed on S. rankanensis, possibly because growing in shade means they fail to develop or ripen. The only propagation success I've had is from basal shoots earlier in the year. Strobilanthes don't appear to attract the attention of slugs or snails. Plants hold their shape well and have no need of staking but the soft outline benefits from more architectural neighbours – maybe spiky Iris foetidissima ‘Citrina' or golden Carex ‘Everillo'.

This is a member of a neglected species which deserves wider recognition. Flowering plants that appear late in the year, particularly those that flourish in shade, are worth seeking out. This would make a good addition to an autumn border where its soft lavender blue would be the perfect foil for brasher and brighter residents, such as helianthus, dahlia, rudbeckia and chrysanthemum, or any other of the jolly crowd that make autumn such fun.

Posted by Gill Mullin