The Smaller Bistortas

Bistorta makes up the largest chunk of the ornamental Polygonaceae. To make life easier I’ve decided to split the genus into two halves based on their typical height in cultivation. Here we discuss the smaller members of the genus, shrubs and herbaceous species that grow up to 30cm tall. All species here have a spreading habit, with low foliage and inflorescences above.

While one species is definitely for a woodland garden or a shaded container, the rest are species regarded as being rock garden plants. Two crucial things must be considered: firstly Bistortas like drainage but do like lots of water during their growing season, and secondly all need plenty of space to form carpets of growth. None in this particular entry can sensibly be called ‘invasive’. Please note that the taxonomy of these plants has been convoluted, and quotes will refer to them as ‘Polygonum’.

Bistorta affinis

Aspect: full sun (if moisture allows) or part shade.

Moisture: plentiful during the growing season.

Hardiness: not quite fully hardy; thin stems likely to dry out in very cold winds. See individual entries.Height: around 25cm.

Although Bistorta affinis was first described in 1825 and introduced into cultivation at some point in the 1840s, it was only really in the 20th century, when better cultivars were introduced, that their popularity really took off. There is a lot of confusion within this species; so far I’ve not physically seen ‘Donald Lowndes’ and I’ve only seen one plant that I’m convinced is really ‘Darjeeling Red’. Even ‘Superba’, the second most recently introduced cultivar, may actually be several clones under the same name, while ‘Kabouter’, the most recently introduced cultivar, looks incredibly similar to ‘Superba’. Cultivars can vary in size, flowering etc, depending on growing conditions; this makes it very difficult to be sure what you’re growing. That said, ‘Darjeeling Red’ and ‘Donald Lowndes’ have notably fatter inflorescences which should make them easy to identify.

During an online talk about the flora of The Silk Road, Christopher Gardner showed us a photograph of Bistorta affinis growing in its native habitat with Geranium himalayense. The effect was really quite attractive and would probably be worth recreating in cultivation. This species is also very effective grown as groundcover under shrubs, particularly in damper climates; this species and its cultivars will flower better in sun but will still make an effort in all but the deepest shade. In the damper regions this species is often seen draped over stone walls to great effect too.

Bistorta affinis in its autumn finery

‘Darjeeling Red “Flowers pink turning crimson”- GST (HPS). In cultivation 1962 (RHSJ1962p336). RBGE received plant in 1966 (RBGE 661918). The size of these flowerspikes should be comparable to those of ‘Donald Lowndes’ (below), but I’ve only seen this once. Plants under this name are sold fairly widely but seem to always have narrow inflorescences (around 1cm wide). The clone is regarded as not being fully hardy.

‘Donald Lowndes I’ve never seen this plant, despite there being plants sold under this name in cultivation. John Carter, former National Collection holder, described this clone as having “almost double pinkish salmon flowers”. This clone is not regarded as being fully hardy. I have found some fairly detailed information, which is unusual when it comes to cultivars in the Polygonaceae! It received the Award of Merit from the RHS in 1957.

“Introduced from Nepal by Colonel Lowndes in 1950 under the collector’s number L.1357 is the true (P) affine. It differs from the plant usually grown in gardens under that name in that the flowering stems are shorter, the flower heads are broader and the flowers themselves larger. It also has a different geographic distribution. In the pan exhibited there were thirty-three flowering spikes, just over 8 inches high, the inflorescences being 2½ inches long and ¾ inch across. The colour varied from Spinel Red to Fuchsia Pink or, even paler, Rose Pink. The lanceolate leaves, glossy green above and pale green beneath, measured 4½ inches long, including the petiole, and ¾ inch across, the margins being slightly serrate. Exhibited by Major and Mrs Knox Finlay, Keillour Castle, Methven, Perthshire.”

RHS Journal 1957, p162

“This excellent form of the species, which had originally been introduced c. 1845, was collected in 1949 by Colonel Donald G. Lowndes in Central Nepal. While the older form, figured in Botanical Magazine t. 6472 (1880), and still widespread in gardens, has relatively narrow flower spikes about 1cm broad, ‘Donald Lowndes’ has thicker spikes and larger, deeper pink flowers, making is a much more striking plant. It seems to be representative of the eastern forms of the species, sometimes accorded varietal rank as P. affine var. affine, while the older introduction more closely resembles the western forms given specific rank by Meisner as P. brunonis but more generally regarded as a varietal form only (P. affine var. brunonis).
It is not known how many seedlings were raised from Lowndes’ collection, but presumably sufficient to ensure some variation among plants bearing the names ‘Donald Lowndes’. Indeed it is not clear to what extent the plants in cultivation are derived from one or a few clones: but this need not concern the gardener as variation is not great.
P. affine ‘Donald Lowndes’ is a very easy plant in any well-drained soil in a sunny or partly shaded situation, forming effective ground cover in the larger rock gardens or between shrubs. Spread is rapid but the free-rooting, suckering shoots and a large patch can be soon built up from a few rooted fragments. It is semi-evergreen, the senescent leaves of every shade of red, brown and gold remaining on the plant throughout the winter. The 15cm flower stems, very freely borne as the illustration [p164] shows, appear over a long period from May onwards, the flowers opening pink but darkening to brick red and finally yielding to brown fruits, which many will consider almost equally handsome and which retain interest well into the winter. There is a very similar cultivar known as P. affine ‘Darjeeling Red’ and which to choose is a matter of personal taste. Either will prove useful and easy and will prolong colour in the rock garden after the early flowering glories have come and gone.”

John Good, Journal of The Alpine Garden Society, 1982 p162

Not everyone, it seems, was a fan…

“’Donald Lowndes’ can look very good indeed at the front of a border. It is mat-forming and its upright flower spikes are continuously produced and continually changing like Sedum [now Hylotelephium] ‘Autumn Joy’ from pink to burnt red. I can only say that when I tried it, it did none of these things- was reluctant to flower and was a miserable failure. I enjoyed throwing it out.”

Christopher Lloyd, RHS Journal 1973, p302
Bistorta affinis ‘Donald Lowndes’ (AGSJ1982p164)

‘Kabouter’ Kabouter is a Dutch word for Leprechaun, although it was also the name of a Dutch anarchist group in the 1970s. I’m going to assume that the cultivar was named for the former and not the latter, but who knows?! This cultivar appears to be a somewhat more compact version of B. affinis ‘Superba’, apparently only reaching 20cm in height. I’m not convinced how truly ‘different’ it actually is, as B. affinis ‘Superba’ can be variable in different growing conditions. Certainly having seen this plant next to the latter I can’t say there’s much difference, especially as I’m not entirely convinced that ‘Superba’ as a clone is entirely on firm ground.

“Persicaria affinis ‘Kabouter’, called Kabouter in Dutch, is a beautiful hardy perennial that produces beautiful red flowers in the months of June to September. The maximum height of the plant is 25 cm. The plant likes a sunny to semi-shady spot. In winter the plant dies. Cut the plant back completely in the spring, then it will sprout again.”

Tuinplant Website

‘Superba’ and ‘Dimity’ (I’m lumping these together because ‘Dimity’ is considered a synonym of ‘Superba’.)

‘Superba’ was introduced to the UK by Graham Stuart Thomas from Hagerman’s of Hanover some point before 1981. Either the clone was unnamed at the point of introduction or GST shared material without passing on the name, because Valerie Finnis was given material and named it ‘Dimity’. Whether Finnis considered the clone in her garden to be different from the one GST had named or whether she believed in good faith that she was giving a name to the plant for the first time we can’t be sure. Plausibly Finnis might have received material from GST and found that under her own cultivation the plant behaved differently to the same plant grown elsewhere; subtle changes in stature are a feature of this species. The plant made it to Alan Bloom who recognised that it was a significant improvement on ‘Donald Lowndes’ and ‘Darjeeling Red’, both of which Bloom found less than completely reliable in his garden. (‘Alan Bloom’s Hardy Perennials’, p100). It’s worth mentioning at this point that in Bloom’s ‘Hardy Perennials’ book ‘Dimity’ is mentioned under the section ‘A-Z of plants raised by the author’- there’s no mention of Finnis here. (Neither ‘Donald Lowndes’ nor ‘Darjeeling Red’ have been regarded as fully hardy, and Bloom’s garden at Bressingham, Norfolk, UK, can get very cold; ‘Superba’ is a marked improvement in this respect.)

‘Superba’ is definitely an improvement on the species; in the same way that ‘Darjeeling Red’ completely overshadowed the species itself for many years, so too ‘Superba’ has become the most frequently encountered clone in cultivation. Part of me suspects that the clone has become less than pure over the years, with good forms of B. affinis and occasional seedlings of proper ‘Superba’ getting mixed in. This is very difficult to assess in any meaningful way as the species is variable under different cultivation conditions (sun/shade, damp/dry etc), and it would rely on pinning down a specific plant as being a ‘real ‘Superba”. Certainly on the Wisley trial bed there was variation with one clone producing inflorescences around 7cm long and another around 8cm long despite the overall height of the plants being around 25cm.

Bistorta affinis ‘Superba’ in summer

By comparison, one clone of ‘Dimity’ had flowerspikes 8cm long while the other was closer to 5.5cm long; clearly there’s variation according to growing conditions but as I said above I think there’s a lot of confusion over the naming of clones within this species.

Bistorta emodi

Aspect: part shade.

Moisture: plentiful during the growing season.

Hardiness: disputed. Probably not as hardy as B. affinis.

Height: around 25-30cm in time.

This is definitely the rarest cultivated species I’ll cover in this piece, and it’s the first of two shrubby species that we find in the genus Bistorta. Despite first being described in 1832 this species has never really taken off in cultivation. It’s not entirely unfair that it has been overshadowed by B. affinis; B. affinis is the more resilient plant and arguably has the more attractive flowers.

B. emodi is found from Kashmir to South Western China, at altitudes of 2,500-4,000m, typically growing around rocks in damp forests. It’s superficially similar to B. affinis but, aside from having a rather more mounding, shrubby habit, it is recognised by its narrower, usually glossy foliage that is usually less dense. I suspect it’s somewhat less floriferous than B. affinis, so the B. affinis cultivars are considerably better garden plants. That said the mound of foliage and the more subtle inflorescences of B. emodi are not unattractive. Typically inflorescences are 5-10cm above the foliage, although individually they tend to be around 3cm long and, certainly in my form, are a matt red.

Reginald Farrer, in The English Rock Garden (vol. 2), recommends lifting rooted layers and overwintering them in a cold frame in all but the milder regions. Certainly this would be easy to do with more established plants, but it might be worth sheltering young plants during their first few winters if circumstances allow. In A Plantsman In Nepal, Roy Lancaster describes seeing B. emodi on the Milke Danda ridge, growing down a wet rock face. He goes on to recommend B. vaccinifolium as the better garden plant for its freer flowering and better habit, and particularly rating B. vaccinifolium as the hardier plant, echoing Farrer’s observations.

My B. emodi has matt crimson flowers; I haven’t found any mention of other flower colours or shades, and given how colour variation isn’t a big feature of the genus Bistorta generally (notable exception being B. affinis) I suspect that this is the uniform colour of the species. My form was collected many years ago from the Mago Gorge, Tawang, Aranachel Pradesh, but in the United States there is a form that was collected under the collection number MD97 by Far Reaches Farm in 1997. Their form, which I doubt is in European cultivation, was found found growing with Polygonatum verticillatum, Rhododendron edgeworthii and Hypericum urabum on a mossy boulder at 10,000ft (3,048m) in the Cangshan region of China. Far Reaches Farm also saw the same species at 12,000ft (3,658m) in Bhutan.

Bistorta tenuicaulis

Aspect: part shade/full shade

Moisture: abundant during the growing season, less in winter.

Hardiness: probably not fully but happy if sheltered.

Height: 15cm in optimum conditions.

This diminutive woodlander is best described as ‘cute but largely uninteresting’. Native to the moist deciduous forests of South Korea and Honhu, Shikoku and Kyushu, Japan, although this species was introduced to the UK from Korea by Mr Amos Perry in 1946.

Maybe I do this species a disservice? Compared to the other colourful and conspicuously showy Bistortas this is a little plain, but it is not entirely without merit. As a groundcover for shade it is very pleasant, forming great carpets over time yet rarely causing a nuisance to any but the smallest woodland plants. It’s also a nice plant for a shaded container, where the tiny (2cm) creamy white inflorescences can be admired closely. If you are looking at this species closely when it’s in flower then you might discover a charming sweet mellifluous perfume; to my knowledge this is the only perfumed member of the genus Bistorta.

I’ve lost this species in the past due to poor watering, too little in summer then allowing it to get waterlogged in the winter. B. tenuicaulis would be happiest in a fairly free-draining humus-rich soil, and associates well with all but the smallest ferns and other woodland plants.

Bistorta vaccinifolium

Aspect: sun/part shade, depending on moisture.

Moisture: abundant during the growing season; prefers good drainage.

Hardiness: probably not for the very coldest regions.

Height: around 15-20cm

The second shrubby species in Bistorta, and possibly my favourite of the smaller species. This short but wide-spreading Himalayan shrub is a delight in the cooler, maritime climate areas of the UK. I first met this species many years ago at Hergest Croft in Herefordshire, UK, where it grew under shrubs in a raised bed. Subsequently I’ve come to know the spectacular plant on the Alpine/Tea Room terrace at RHS Rosemoor in Devon, UK, very well.

Bistorta vaccinifolium at RHS Rosemoor, Devon

This species did not enjoy its time on the trial bed at RHS Wisley; a combination of full sun, not entirely adequate watering and a free-draining soil were about as wrong for this species as you could possibly get. Conversely a plant in a partially shaded pot display elsewhere in the garden was thriving, proving to my mind at least that the species just wasn’t happy with other trial plants.

Bistorta vaccinifolium has had its advocates over the years. It’s not uncommon to find it mentioned in articles and books with great fondness, if with the brevity reserved for the cultivated Polygonaceae in general. It’s rare to find gardeners willing to admit to a love of anything Polygonaceous at the best of times; usually a writer will mention a favourite plant quickly and then move on, as if fearing the wrath of the more populist plantspeople. Some brave souls have, thankfully, been willing to confess their unorthodox love.

“[Bistorta vaccinifolium is] very distinct in aspect, quite hardy, and thrives is almost any moist soil, but is best seen where its shoots can ramble over stones or tree stumps. Under favourable conditions it grows rapidly, and produces a profusion of whortleberry-like [dwarf Vaccinium-like] leaves and rosy flowers in September and October, when it is valuable in the rock garden.”

The English Flower Garden, William Robinson

“Finally for the rock garden, I recommend a useful and rewarding subject invaluable for its autumn colour, both for flowers and foliage. Polygonum vaccinifolium- the genus was formerly Bistorta- is found from Kashmir through to South Eastern Tibet. Forming trailing mats, this one must be given space to spread amongst and over rock work. Keep it clear of the confines of a raised bed. Should it spread further than planned, a little surgery will resolve the problem. Slender racemes of soft pink flowers appear in late summer and autumn, and the small leaves assume lovely red tints in the autumn months.”

The Himalayan Garden; Growing Plants From The Roof Of The World, Jim Jermyn

Even Reginald Farrer, whose kindness towards species wasn’t always assured, gives notable space to celebrating this species.

“[Bistorta] vaccinifolium not only escapes the charge of coarseness to which this race is open, but escapes it so handsomely as to be one of the loveliest and most refined treasures in which the garden rejoices. All the year it is lovely, in any sunny place in good soil, making close carpets and cataracts over the edge of the rocks, with its long, woody trailers, set with narrow, glossy, evergreen[?!] little leaves of the heartiest and most immortal appearance; and then, in autumn, there breaks up, on stems of 2 or 3 inches, so unbelievable a profusion of little rose-pink spikes that the ground and the green below are almost hidden from view; and when in their midst tower up also the violet wide goblets of Crocus pulchellus or C. speciosus Aitchinsoni among the crowded pink spires, the sight it one to make even the most sedate give tongue. This beauty requires careful propagation by cuttings, and should not be put in too exposed a position in the garden’s battlefield, as, though perfectly hardy, it repays a sheltered slope or ledge, and insists on fullest sunshine if it is to repay you with its fullest generosity of flower.”

The English Rock Garden (Vol.2), Reginald Farrer