Nomenclature in the Genus Libertia – from Stephen Butler
When I first started work in Dublin Zoo there were considerable numbers of various waterfowl, particularly geese, which I soon found ate everything – even the bark from young saplings in winter can be stripped. Trying to get any grass established was virtually impossible, all we ever managed was a thin skin, a veneer of green, on muddy, puddled – and over fertilised – soil.
One plant – at goose height – seemed immune. A large clump of what we then called Libertia grandiflora not only survived, it thrived, and I was soon saving seed and growing on hundreds more. With a small plastic fence to keep geese off for a year or two to let young plants get established, we soon had a green ribbon, looking good when in flower, around our lake, and behind that we could get better grass too as the geese had less access. For a simple planting it worked very well.
I then became involved with Plant Heritage (National Council for the Conservation of Plants and Gardens as it was then) and started thinking ‘which plants could I justify collecting in the zoo’? Libertia came to mind, it seemed a small enough number of species, readily available, shouldn’t be too much work or too hard…Seldom have I been so wrong in an assessment!
The garden books seemed to list only a few species, L. caerulescens, chilensis, formosa, grandiflora, and ixioides. Several more were listed in the Plant Finder. L. chilensis was listed as a synonym of L. formosa. I could see no difference between what I had bought as L. chilensis, formosa, and grandiflora. When I sourced L. caerulescens it did not look like a Libertia at all. I was given seed from a plant labelled L. breunioides, but could find no listing for it; no description either. The same for L. procera, nothing found on where the plant came from, or what it would do, and it looked like what we had as L grandiflora on steroids.
So I started collecting, deliberately sourcing several accessions of the same named species to see what different nurseries were selling, and also getting seed in where I could from the countries of origin – mainly Chile and New Zealand. But after asking for L. tricocca and receiving a packet with L. chilensis crossed out, and L. tricocca written in instead, I did not have much faith in that batch or that seller!! After several years I applied for and received National Collection status from Plant Heritage, and I started going on about the names being a mess, and a review would be in order.
In the meantime, with reviews published in New Zealand covering their native species – and naming several more – I reckoned I had sorted out some of the names, but was still thoroughly confused with the grandiflora/chilensis/formosa/procera accessions. Plants sold as L. caerulescens were always either L. sessiliflora (the only blue Libertia), or, more often, Orthrosanthus laxus a different genus entirely. L. breunioides turned out to be L. cranwelliae, which I had grown from seed supplied from New Zealand. L. procera had turned out to be a most vigorous plant (procera means tall), with larger flowers, flower stems to 6ft, and it seemed hardier in very cold winters. The 2 severe winters of 2009/10 and 2010/11 hit most of the Libertia hard, especially L. sessiliflora, but they all came back, though we needed to spend ages removing dead leaves.
In 2013 the Royal Horticultural Society contacted me with a request to assist with a review of the genus, and I happily supplied pictures and herbarium specimens of all those I had. Preparing the specimens, with some initial assistance from the National Botanic Gardens at Glasnevin – I had not done this since a student at Kew – was a very time consuming task, but it was instrumental in getting the review successfully completed. Each pressed specimen was not only mounted, but had pictures, and a detailed sheet attached, with colour and dimensions of leaves, roots, flowers, even pollen colour can be useful.
The review was published in The Plantsman (RHS) in June 2015, Volume 14 Part 2, with detailed botanical descriptions as needed. I’ll give a less detailed account here, but generally follow the order in that review, leaving out the more obscure species that are unlikely to be found in our gardens, with a brief list of confused names first:
- L. breunioides – see L. cranwelliae
- L. elegans – see L. chilensis
- L. formosa – see L. chilensis
- L. grandiflora as commonly grown in gardens – see L. chilensis
- L.procera – see L.chilensis
- L. caerulescens – see L. sessiliflora
Libertia cranwelliae – found under the name L. breunioides, a name not recognised and no one seems to know how, when, or where it was named. I sorted this out by the simple expedient of ordering seed from New Zealand, and when L. cranwelliae grew it was identical to L. breunioides. The leaves are a brownish colour unless in shade, the plants spread by orange coloured stolons, readily forming a dense colony. Large white flowers produced after at least 2 years from seed, are held at half the leaf height, and the large round seed pods are held tight shut until the following spring (with us anyway).
Libertia chilensis – this is the complicated one, a very variable species, widespread in Chile, and the commonest species in cultivation. It is usually grown under the names L. grandiflora, or L. formosa, and sometimes L. elegans and all are technically incorrect. The confusion stems from a description in 1856 by Philippi, who was unaware that the specific epithet grandiflora had been already used in New Zealand in 1810 for a different species (but under the genus name Renealmia). The formosa and elegans epithets come from a description in 1833. The chilensis epithet was published first in 1810, but under the name Strumaria chilensis. L.procera is a name not recognised – it means tall and it is – and again the origin of this name is not known. You can see why I was confused, and had to have botanical taxonomy assistance! All flowers are white; green leaves vary from 35cm to 75 cm depending on group below. No stolons produced.
With so much variability this species has been split into 3 groups as below.
- chilensis Elegans Group. A shorter plant than usual, with a more open umbellate inflorescence. It is not that often found in cultivation, but has been found as an escapee in the UK.
- chilensis Formosa Group. This is the commonest form, very widely grown and very variable in flower size, bud colour, and stem colour. If propagated vegetatively you get a clone that is distinctive and there are a few listed. I have seen plants grown from seed collected in Chile that, within 6 seedlings, had 6 slightly different plants, proving the variability was inherent in the natural population.
- chilensis Procera Group. The tallest most vigorous grower, with larger flowers that look me in the eye and I’m 6ft 2in. We regard this at Dublin Zoo as L. chilensis on steroids, and if we want more plants we use this as seed source now.
Libertia grandiflora – the true species – is very seldom seen in cultivation, but I do have some at Dublin Zoo, kindly donated by Pine Lodge Gardens in Cornwall as L. paniculata, and very kindly transported here by an Irish family returning from holiday as the nursery did not do mail order, which key out to the true L. grandiflora. This is a much shorter plant, green leaves to only 25cm at most, 1 – 6 white flowers per panicle, more open than the usual L. chilensis above. It is self-infertile, so it is harder to get seeds for increase. The flowers are white but it is shy to flower.
Libertia ixioides is distinguished by stiff leaves that are not green but quite brightly coloured, with yellow, orange and reddish brown shades, and therefore popular with nurseries as they sell well on looks alone. No stolons are produced. Several cultivars are in the L. ixioides Tricolor Group, produced in New Zealand. The specific epithet tricolor comes from a specimen named first as Sisyrinchium versicolore in 1863 and renamed L. tricolor, also in 1863. The flowers are white.
Libertia peregrinans is commonly grown, and easily recognised by vigorous stolons, quickly forming an open colony of fans of leaves. The leaves are green in shade, but a distinct copper colour in sun. There are cultivars with slight differences in leaf colour.
Libertia sessiliflora is easy to distinguish as it is the only blue flowered species! As the name says the flowers are sessile, no stalks, and form a very tight bunch and are less, to my eye, ornamental for that. There are different shades of blue available and the darker one look better as the pale ones can look washed out. We find they suffer more in a really cold winter, with almost all leaves going black. Plants have been sold as L.caerulescens for many years but any I have bought have been either L. sessiliflora or, worse, actually Orthrosanthus laxus! This has 6 petals, rather than the usual 3 for Libertia, of a most exquisite blue but we find the plants are short lived after flowering well for a year or two.
Libertia umbellata is again easy to distinguish, as it is the only white flowered species with only green leaves (with a slight pale sheen) that produces stolons, gently forming a dense stand. The flowers are to my eye more decorative, held slightly more loosely than L. chilensis in any form. Julian Shaw sent me a scan of a herbarium sheet from 1871, from a Chilean collection, asking if I had this one. In the scan the stolons were very visible; it had a delicate flower head and was very easy to recognise, but it was labelled as the New Zealand species L. ixioides, and was assumed at that time to be a cultivated introduced plant there!
Libertia x butleri – I suppose I have to include this! If you cross L. chilensis and L.ixioides you get variable hybrids – one in the trade is named ‘Amazing Grace’. These arise spontaneously and we have several at Dublin Zoo now which we have noticed are a little bit different. They had come from seed collected either by ourselves or a plant producer we know and grown on for us, about 2000 or so, so there is no sure way of tracing back the crossing. Julian Shaw needed to put a name to this garden hybrid, and mine was handy, and I’m told recognises the amount of work I’ve put into the collection.
To conclude, if I had not decided to gather enough Libertia to form a National Collection I would never have seen the range available and certainly would never have realised the naming issues. Like many others I bought plants under the wrong name many times. I’m told this is the general chorus from all National Collection holders. If you have an interest in a particular genus, why not start collecting; it can become addictive, be warned, but ultimately worthwhile and, dare I say, rewarding!
Stephen Butler is the Curator of Horticulture at Dublin Zoo, Phoenix Park, Dublin 8, Ireland and you may correspond with him on this topic via that address should you wish to do so.