INTRODUCTION TO THE COMPOSITAE – 3

Abstract

This is the third part of Curtis's Botanical Magazine devoted exclusively to the Compositae in recent years, and a substantial amount of this issue has been written, painted and illustrated during the various Lockdowns of the COVID-19 pandemic that so badly affected everyone during 2020, 2021 and now 2022. Whilst pulling together suitable species for this issue, some had been assessed long before the pandemic was on the horizon (Senecio squalidus L., Tanacetum densum (Labill.) Sch.Bip. subsp. amani Heywood), some during the Lockdowns (Klasea cerinthifolia (Sm.) Greuter & Wagenitz, Echinops wakhanicus Rech.f., Launaea cervicornis (Boiss.) Font Quer & Rothm., Inula rhizocephala Schrenk), and others after the second Lockdown had ended, and some of the artists ventured out for the first time in many months (Centaurea cineraria L. and Helichrysum bellum Hilliard). What became obvious was the difference in the working environment. BC (Before COVID), Kew was bustling, rarely quiet, and the Herbarium a veritable hive of activity. In the Gardens, during the Lockdowns, there was a surreal peace and quiet – no planes, no trains (either Underground or above ground), and little traffic noise (save a little from the elevated section of the M4 running past Brentford on the north side of the River Thames), birdsong, or the noise of anyone in the Gardens – except the occasional gang mower. The plants in this issue are ordered according to their position in the generic list for the family used for curation in the Herbarium at Kew. All the tribes have been illustrated in earlier Compositae-only issues, and some of the species may be well-known to many, although others are comparatively, or very, rare in cultivation, and certainly deserve to be better known and more widely cultivated. Three articles are of members of the thistle tribe, the Cardueae, possibly better known in temperate regions for pernicious weeds (many Cirsium spp., the true thistles), some often quite spectacular cultivated plants (cotton thistles – Onopordum spp., globe thistles – Echinops spp., and even some Cirsium spp., especially one from Mexico, such as Cirsium mexicanum DC., the ubiquitous C. rivulare (Jacq.) All. cv ‘Atropurpureum’, or even the showy, biennial, red-flowered Cirsium occidentale (Nutt.) Jeps., the western thistle, from California), and rarely as crops (the globe artichoke and cardoon – Cynara carduncellus L.). The first of those illustrated here is a relatively recently collected species, Echinops wakhanicus Rech.f. (Compositae: Cardueae: Echinopsinae) (Hind et al., 2022a), one of two species (see Inula rhizocephala, the last article) illustrated in this issue that were collected as seed on a joint collaborative expedition in 2018, with Kit Strange (then from RBG, Kew), John Mitchell (Royal Botanic Garden, Edinburgh) and staff of the Kolub Botanic Gardens, Tajikistan. The seed of both species was grown on by Kit and both potted up, and planted out, material was used by the botanical artists for the plates and text figures. Echinops wakhanicus is worthwhile considering for cultivation as it is one of the few pure white corolla'd species of globe thistle that might be met with. Cultivars of E. ritro L. do exist, but have much larger synflorescences, but they never develop the fierce spination found on larger and older ones of E. wakhanicus – together with the vicious spines on all leaves that can catch you unawares. Although Echinops wakhanicus spans the borders of Afghanistan and Tajikistan, its Conservation Status (of Endangered) in Tajikistan is not reflected in the species' wider distribution on the other side of the Panj River in Afghanistan, where we consider it is of Least Concern. Certainly, the large, often dense, populations throughout the valley bottom would support this. Whilst the genus Centaurea L. is a moderately large genus of some 500 species, including both weeds (often the most spiny species) and plants of horticultural interest, relatively few have been illustrated in Curtis's Botanical Magazine. Illustrated in this issue is a long-cultivated species, although Kew's material of Centaurea cineraria L. (Compositae: Cardueae: Centaureinae), caused some consternation when I first examined it and compared it with many of the images and accounts on the internet, and perhaps not unsurprisingly so. Our stock is clearly material from the Centaurea cineraria group, and some might place it close to Centaurea gymnocarpa Moris & De Not. However, the presence of densely sericeous achenes and a short pappus would preclude the latter, although I suspect our material may well be of hybrid origin. Centaurea gymnocarpa is a relatively narrow endemic, from the Isola di Capraia, in the Tuscan Archipelago National Park, and is restricted to eight populations – hence its conservation status of Vulnerable. The article on this species has, once again, highlighted the many issues of uncritical information on the web. As one of the many plants that is often called dusty miller, along with species of Senecio L., the use of common names is commented on. The careless use of images of other completely different plants is also noted with a yellow-flowered Cretan species most probably illustrated. The third member of the thistle tribe is Klasea cerinthifolia (Sm.) Greuter & Wagenitz, a not unattractive, yellow-flowered species like Centaurea africana L. (Hind, 2019), which also has a moderately long history of cultivation – some 210 years. This long history has led to a not inconsiderable confusion with a medicinal herb, Centaurea behen L., a sympatric species across parts of their distribution, especially around the ancient city of Aleppo, Syria; this confusion is discussed, and the history of the two in the literature outlined. The Klasea is now rather rare in cultivation, and apparently not commercially available. The Lactuceae, with c. 98 genera, containing c. 1550 species (depending upon the species definitions in Taraxacum F. H. Wigg. and Hieracium L.) is well-known for several plants of horticultural merit, as well as the lettuce. Launaea cervicornis (Boiss.) Font Quer & Rothm. (Compositae: Lactuceae: Hyoseridinae) is an endemic of the Balearics, and is the dominant species in the limestone cliff-top plant association on the islands. The reproductive biology of the species is somewhat interesting, especially as the species exhibits a particularly short flowering time (per floret) and flowering period, maximizing on calm periods and an abundance of flower visitors/pollinators. The species possesses three different dispersal mechanisms – anemochory (for solitary achenes), and atelechory (where the achenes remain stuck to the parent plant usually via the wettened pappus setae – something often seen in Sonchus oleraceus L.) and barochory for mature, unopened involucres (where the whole involucre falls within, or not far from, the parent plant). The former ensuring there is some movement away from the parent plant, and the latter two effectively ensuring that propagules are not instantly blown off the cliffs into the sea. The tribe Senecioneae, with c. 140 genera and c. 3000 spp. is perhaps the second largest in the family (alongside the Astereae), and contains many plants of horticultural value, and a host of pernicious, sometimes highly toxic, weeds. Amongst the latter are the ragworts, including the subject of one of the plates in this issue – the Oxford ragwort, Senecio squalidus L. (Compositae: Senecioneae: Senecioninae). It is a widespread, diploid hybrid species with strong self-incompatibility, that originated in the British Isles within the last 300 years. The species has an interesting history, and doubtless originated from hybrid material originating from Mount Etna on Sicily. The spread of this plant in the British Isles has led to the presence of several natural hybrids as the plants spread out from Oxford. I have provided two synonymies, one of the species originating in Britain, the other, fuller, synonymy is that of the morphological species encompassing its broader concept within Europe, including the hybrid swarm, between S. aethnensis and S. chrysanthemifolia, on Mount Etna, Sicily. The tribe Anthemideae, with c. 115 genera, and c. 1900 species, is best known for a large number of aromatic plants, many with pharmaceutical and/or pesticidal properties. Many taxa are hardy, and some, such as Chrysanthemum L., are widely cultivated and hybridized. Cotula L., a genus of some 60 species is widespread (southern and eastern Africa, Australia, South America, Mexico, and the southern oceanic islands), although few are cultivated. Cotula coronopifolia L. is widespread, and can be useful in humid environments – and I have found it growing quite happily at about 3500 to 4000 m above La Paz, Bolivia, along a roadside ditch in the Altiplano. Other perennial species are useful ground-cover plants, just as species of Leptinella Cass. can be. Tanacetum densum (Labill.) Sch.Bip. subsp. amani Heywood (Compositae: Anthemideae: Anthemidinae) is the representative of this tribe in this issue of Curtis's. Our Kew stock of this plant appears to be amongst the oldest of any covered in this issue, dating from before 1958, less than a decade after it was first described. The genus Tanacetum Sch.Bip. includes many species once placed into Pyrethrum Zinn, and includes the source of the insecticide containing pyrethrins. Whilst undertaking the literature research for this article, by happenstance I appear to have worked out that Medikus's homonym of Pyrethrum most certainly belongs in the tribe Heliantheae, not Anthemideae, and may be close to Acmella Rich. or Spilanthes Jacq., both genera containing species common in marshy or damp habitats. This issue contains articles on two members of the Inuleae, often called the everlastings, a tribe of c. 250 genera, containing c. 2900 species. The first, Helichrysum bellum Hilliard (Compositae: Inuleae: Gnaphaliinae), belongs to one of the largest genera in the tribe, Helichrysum Mill., with c. 600 species. The genus is now considered restricted to the circum-Mediterranean area, south to southern Africa and Madagascar, with a few outlying species in Central Asia and India. Helichrysum bellum is one of a small cluster of species in the species-rich Drakensburg Alpine Centre, each appearing to inhabit a particular ecological niche, and all characterized by their pure white, multiseriate phyllaries, and often rosettiform leaves. A close examination of H. bellum has shown that, even when described, one other feature of this group, the cerise colouring at the base of the white upper portion of the phyllaries, was missed. In the final article in this Compositae issue, Inula rhizocephala Schrenk (Compositae: Inuleae: Inulinae) (Hind et al., 2022b) is described and illustrated. Inula L. is now considered to be a genus of between 70 and 80 species, including a strange group of species from southern Africa, some of which flower before leafing (and produce the most enormous leaves when they do). This Asiatic species is unique in the genus in its squat habit, wheel of rosettiform leaves and a near-sessile inflorescence of many bright yellow, radiate capitula. This is not the first stock of this species grown at Kew over many years, perhaps suggesting that it is not a perennial. Its habitat, at least in Tajikistan, is with its roots in water, suggesting that we may not keep it well enough watered. Sadly, I think that either the slugs or snails put paid to the last of the plants in the Rock Garden, either them or over-zealous weeding and removal of damaged plants. Where are they now? a retrospective – what's happened to a sample dozen of the plants illustrated in earlier issues? Over the last three decades or so I have written up one or two ‘plant portraits’ for Kew Magazine and then Curtis's Botanical Magazine. I thought that it might be interesting to see how some of the plants fared in cultivation, both at Kew and some of them in the author's garden in Reading. I have listed the plants more or less in systematic order, and all are referenced at the end of this, my ‘Introduction to the Compositae – 3’. Cultivated representatives of the most primitive subfamily and tribe, Barnadesioideae and Barnadesieae respectively, are rare, and now decidedly rarer. Barnadesia arborea Kunth (Hind & Hall, 2003: Plate 459) – alas, this once interesting plant has succumbed to the ‘deaded’ entry in the Living Collections database. The original coppiced stock was transplanted from the old Alpine House to the then new Davies Alpine House where it thrived, as a somewhat thuggish plant, overgrowing and smothering many plants beneath it. It was removed and it was rumoured to have been planted in the frost-free shrubbery adjacent to the boundary wall near the old Cumberland Gate. How many readers remember accessing the Gardens via that hole in the wall? I never saw any sign of its planting, and can find no sign of its continued existence. Centaurea africana L. (Cardueae: Centaureinae) (Hind, 2019: Plate 914). Although I had no experience of growing this plant in Reading, I felt happy that the Kew accession, dating from 2011, was a survivor. Alas, no. In trying to see how well it was doing this COVID-summer I could not see it on top of the exposed bed next to the Davies Alpine House. An enquiry finally resulted in being told that the plant had not been moved but had been ‘deaded’ – by an unknown cause. Possibly the ants nest providing the frequent visitors to the capitula had moved too close to the rootstock? Last winter's mild weather (2020/2021) is unlikely to have been the reason. Centaurea clementei DC. (Cardueae: Centaureinae) (Hind & Walters, 2006: Plate 569) has, I am pleased to say, gone from strength to strength. Stock material, originally grown in Glasshouse A1 was planted out in the Davies Alpine House and grew to epic proportions on a ‘rock face’ before becoming a little too woody, and its subsequent removal. However, additional propagated stock of the same clone replaced it, and several plants have also been trialled in the European section of the Rock Garden – and, at the moment, appear to be thriving. The tribe Arctotideae is one of the smaller, containing about 17 genera and a little over 200 species; it is predominantly southern African. The two largest genera are Arctotis L. (c. 60 spp.) and Berkheya Ehrh. (c. 80 spp.), with very few species in cultivation. Gazania rigens (L.) Gaertn. is well-known as a garden plant, and a handful of species of Osteospermum L. and Dimorphotheca Moench are common in gardens, albeit with a little protection; cultivars are not infrequent. The few Arctotis in cultivation are relatively tender. Berkheya is perhaps the more spectacular in that they are thistle-like, but relatively few are hardy in the temperate climate of the British Isles, Northern Europe and parts of North America. Arctotis ‘Nicholas Hind’ D.J.N. Hind (Arctotideae: Arctotidinae) (Hind, 1992: Plate 207) – alas, this cultivar no longer exists at Kew. Material was no longer propagated following the original mass-planting and the occasional planting alongside the west wall of the Duke's Garden, behind Cambridge Cottage. Within a couple of years, the author's own stock of the plant had succumbed to a cold winter and could not be revived. The story behind its name is covered fully in the original article, and is a source of constant bemusement for the author. Berkheya purpurea (DC.) Mast. (Arctotideae: Gorteriinae) (Hind, 2006b: Plate 568) – this has been a persistent success, having been tormented by me in the same 12″ pot for the last 15 years. It has suffered numerous periods of drought when in its wilted state looked more and more likely to shrivel completely and die. However, subsequent drenching has seen the plant recuperate, and I am pleased to say, although flowering off and on, produced an abundance of flower this second COVID-summer! At Kew, the original stock on the top of the South African ‘mound’ has continued to expand, and several plants can now be found as part of the Compositae plantings down the Great Broadwalk Borders and in the new Evolution Garden – that took the place of the now sadly lost Order Beds. The tribe Vernonieae is also one of the larger in the family, at around 1000 species; the number of genera is a matter for debate as I suspect (and have commented on) is somewhat inflated. Distephanus Cass., with 40+ species has sometimes remained submerged in Vernonia, especially within Madagascar. However, the species are often characteristic with 3-veined leaves and yellow corollas, a rare combination in the Vernonieae. Indeed, the only obvious ‘yellow’ corolla appears in the spectacular Glaziovianthus speciosus (Gardner) MacLeish from the campos rupestres of central Brazil (Goiás State) – but then the yellow is on the inside of the top of the corolla throat, the outside being a spectacular rose-red throughout, and there are ‘heads of heads’ on the top of a relatively long, erect, few-bracted scape. Distephanus populifolius (Lam.) Cass. (Vernonieae: Gymnantheminae) (Hind, 1996: Plate 302). The flowering stem, painted by Ann Farrer, came from a shrub originally growing in the Temperate House. Both Martin Staniforth (who provided the Cultivation Notes) and I noticed that the plant was somewhat infested with glasshouse whitefly. Unfortunately, over time this led to sooty mould deposits developing on the leaves from the honey dew left by the whitefly. Regrettably, the whitefly infestation became too great, suggesting that the decision to use the predatory wasp was made far too late, the sooty mould finally leading to the demise of the plant before it could be propagated. Alas, the plant was ‘deaded’ late in 1996, and has never been replaced at Kew. Cotula fallax D.J.N. Hind (Anthemideae: Matricariinae – the ‘Cotula Group’) (Hind, 2006c: Plate 570). I had managed to keep my Reading stock growing for many years in a large bowl (c. 18 inches in diameter), but with issues of damp, destructive songbirds and assorted weeds, the plant cushion finally succumbed some four or so years ago. However, I'm please to say that in several plantings at Kew (adjacent to the south end of the Davies Alpine House, as well as in at least one of the beds along the Great Broadwalk Borders) the plant has thrived remarkably well, often with a thick ‘turf’ formed by the plants, above which the ‘golden button’ capitula are ‘suspended’. The source of many horticultural plants, and one or two crop plants, the tribe Heliantheae sensu lato, contains about 300 genera and over 3330 species. Modern concepts would have this somewhat natural tribe split asunder, into a ridiculous number of tribes, these perhaps best kept as quite recognizable subtribes. The tribe has been widely illustrated since the earliest volumes of Curtis's, such as Rudbeckia purpurea L., the purple rudbeckia (= Echinacea purpurea (L.) Moench) appearing in Volume 1 as Plate 2. Cosmos Cav. is perhaps better known for three commonly cultivated (and in the tropics, widely naturalized) species. However, some of the more interesting plants are the tuberous rooted perennials, such as Cosmos atrosanguineus (Hook.) Voss (see Hind & Fay, 2003) and the next plant. Cosmos peucedanifolius Wedd. (Heliantheae: Coreopsideae) (Hind, 2005: Plate 532). I managed to keep this plant over several winters under a frost-free covered area behind my house in Reading. After three years, however, it decided it had had enough and never awoke from its winter rest. Doubtless kept too dry, in an effort to avoid frost damage, the tubers had shrivelled beyond the point of being able to be resuscitated. A replacement stock, from the same original source – the Editor, Dr Martyn Rix – fared little better, only surviving a couple of winters. Clearly, overwintering frost-free under glass is a must, and avoiding treating the plants like cacti (and letting them become bone-dry) is a must. Lindheimera texana A. Gray & Engelm. (Heliantheae: Engelmanniinae) (Hind, 1990a: Plate 156), Espeletia schultzii Wedd. (Heliantheae: Espeletiinae) (Hind, 1990b: Plate 158), Senecio formosus Kunth (Senecioneae) (Hind, 1991: Plate 163) have all succumbed to the dreaded ‘deaded’ input into the Living Collections database. Lindheimera texana was one of many annuals whose seeds were religiously collected from the ‘old’ Order Beds, both when there were adequate staff, and Order Beds. Annuals, it would seem, are a thing of the past. Espeletia schultzii and Senecio formosus were occupants of the old Alpine House, the former of one of the refrigerated beds, and the latter one of the border plantings, neither of which were transferred to the ‘new’ Davies Alpine House (formally opened in 2006). The tribe Eupatorieae, of some 185 genera and c. 2000 species, is predominantly a New World tribe, with few native species of the Old World, and a number of weedy, even somewhat pernicious, species in both hemispheres. The genus Ageratina Spach contains c. 270 species, ranging from the southern United States south to Argentina (with a couple of pantropic weedy species); few species are in cultivation, but one of the largest is the following: Ageratina ligustrina (DC.) R.M. King & H. Rob. (Eupatorieae: Oxylobinae) (Hind, 2006a: Plate 567). This has been a resounding success for the author, but not so much for Kew. In its early days in Reading, the original stock was planted in one border of my back garden where it grew remarkably well and was treated to a regular hard autumnal prune down almost to ground level. In the following spring the old growth was soon replaced by young shoots, these flowering later that same year. Cuttings were taken, and once rooted, potted up, much as the Victorians used to, to provide a winter scented plant to bring indoors. I planted one of these in my front garden where it has never failed to impress, in terms of hardiness, growth, and the ability to flower three or four times a year and scent the road in sultry, calm weather for some distance. One pot was also donated back to Kew when I discovered the original plant had ‘died’. This COVID-summer, the Reading plant has now reached its largest size – about 4 × 4 m, and is completely white (at the time of writing this in early September), covered in probably hundreds, of white (possibly slightly tainted pink as the corollas mature) inflorescences, each usually with one or two honeybees (Apis mellifera L.) foraging for nectar throughout the day. During the middle of the day the honeybees are joined by hoverflies, butterflies (mostly small tortoiseshells), and sometimes wasps. It is most probably going to be ruthlessly pruned when it finishes flowering this year (2021). At Kew it has been a different story. The replacement plant, somewhat poorly treated in the Rock Garden, was finally removed. Never having been given proper space, it never looked happy. Maybe a border planting will suit it better if Kew accepts another donation? And, finally, may I offer my own congratulations to one of our artists (and co-authors) in this issue – Ms Masumi Yamanaka. On Thursday 7 October, 2021, Masumi was awarded the Foreign Minister's Commendation at the opening reception of ‘Japan’ in the Temperate House, at the Royal Botanic Gardens, Kew, for her distinguished contribution to the ‘Promotion of Japanese Culture in the United Kingdom’ by His Excellency The Ambassador of Japan, Hajime Hayashi (Fig. 1).