Ruscus Articles

Originally published in the Devon NCCPG/Plant Heritage Newsletter Spring 2009. The caption on page 17 should read Ruscus hypoglossum.

The National Collection Of The Family Ruscaceae Has Been Renamed

The genus Ruscus should really be on the NCCPG ‘missing genera’ list and would still be if Peter Yeo from Cambridge had not researched the genus in the mid 1960s and described two new species. Cambridge Botanic Garden were then in the position of growing all the species and their National Collection was the first.

Following much scientific research over the years the concept of the family Ruscaceae, to which the genus Ruscus belongs, has changed, it has been made very much bigger. My collection contains all three of the original genera, Ruscus, Danae and Semele, the last two having a single species each. The Angiosperm Phylogeny Group (a group of professional research botanists) have put a lot more genera into the family, genera such as Polygonatum and Maianthemum (which now includes Smilacina), making the family go beyond my specific interest. A decision was made to cut Danae and Semele from the collection (though I will still grow both) and concentrate on the six basic species of Ruscus. Danae has a single species, D. racemosa and Semele also has one, S. androgyna, unless you believe some of the literature, in which case you need a yet to be invented, hand-held DNA testing kit to be able to distinguish them. The National Collection is now just Ruscus, my original interest.

The genus is one where the species fall into two clear groups. The British native butchers broom, R. aculeatus, is prickly and has branched stems and there is one related species. The other four species look and feel different, mainly as there are no prickles but also as the stem is not branched. These are used as foliage with cut flowers (as is Danae). What look like leaves and carry the flowers are flattened lateral shoots called cladodes the spine being at the tip, the tiny leaves are at the base of the cladodes and soon wither. All the green parts carry out photosynthesis like the foliage of gorse and the various broom species where the true leaves wither after an initial flush.

The distribution of Ruscus centres on the Mediterranean, Black and Caspian Sea basins extending into northern Europe and out to the Azores and Madeira. Two species are isolated from the rest. The Parrotia woods round the southern shores of the Caspian have the butchers broom relative R. hyrcanus, it has its branches in one whorl not staggered up the stem. In the laurel forests of the small island of Madeira is the rare R. streptophyllus, as the forest is felled the Ruscus dies off.

I started to grow Ruscus after identifying a completely unknown plant while a gardener at the University of Exeter and it was Peter Yeo’s scientific paper from 1968 which allowed the final identification of R. hypophyllum. This is a somewhat tender north African species and was growing at the base of a large evergreen oak. The bulk of my collection came from Cambridge but plants also came from Kew and private individuals.

Various friends regard them as hideously boring and I have difficulty in disagreeing because of the similarities between them but they are used for commercial cut foliage, they have bright red berries in the right circumstances and do grow in the darker, drier places in the garden. With limited space the most commonly grown and most worthwhile is butchers broom, R. aculeatus but if you can get it R. hypoglossum enjoys shade. Danae racemosa is also well worth growing, though is a little difficult to get. The commonest species grown is our native butchers broom. Like most of the genus, male and female flowers are on different plants, so if fruit is required you must trust your nurseryman to sell you the right plants. Butchers broom has produced plants with both male and female flowers, these hermaphrodite plants have been taken into cultivation and should fruit reliably. Some have been named but I have not grown any of the newly named cultivars, the catalogue descriptions make them seem identical. ‘Wheeler’s Variety’ I do grow, as a gift sent from Plant Delights in North Carolina, USA, the fruit was so heavy in 2008 that some weaker stems arched with the weight. R. hypoglossum is listed by four nurseries in the 2008-2009 RHS Plant Finder, none however specify if the plant is male or female. I have only seen a male plant in cultivation, at Joan Loraine’s garden at Greencombe, Porlock where it was producing copious amounts of pollen. My own female plants have started to fruit since the close planting of the male plant.

The only other cultivar of note is Ruscus aculeatus. I first saw this plant at the Royal Botanic Garden Edinburgh. They had received it from C. Sprenger a nurseryman of Naples on 6 April 1904, the garden still has the original 1904 catalogue, Hortus Botanicus Vomerensis. There had been confusion between this and ssp. angustifolius (also known as R. ponticus). ‘Lanceolatus’ is unusual in that the cladodes are long and very narrow, where the length is 5 or more times longer than the width, in the range 18-35 x 2.7-5 mm. The cladodes of both subspecies of R. aculeatus are generally shorter and wider and always less than 3.5 times longer than wide. It is female so should produce fruit if pollinated by any form of R. aculeatus. The full story and my investigation was published in ‘The New Plantsman’ December 2001, 8:4 (239-243).

Six species and a few cultivars don’t make it the biggest National Collection but that was not the reason for trying to hybridise the species, it was more along the idea of ‘will it work?’ and it did. The garden problem of being single sexed, i.e. needing both sexes close by, was a great help in hybridising as normal isolating procedures can be very fiddly due to the flowers being so small. The four species which are non-prickly each occupy their own geographic area so hybrids could not occur between them in the wild but it has been possible in the garden. The result is something of a mess, a mix of minor specific differences. Ruscus aculeatus overlaps with three of them but no confirmed hybrids are known, again, forcing them to hybridise in the garden has been productive, producing various amounts of seed and resultant plants intermediate between the parents that overall look like giant ‘leaved’ butchers broom with a weak spine at the end of each cladode. The biggest problem is the time scale. On average, from pollination to mature seed is 18 months with germination from 18-36 months. In the future if any are worth naming those names will be published. The interesting question is why have no hybrids been found where butchers broom grows alongside other species? But I don’t have an answer.

Division is the best way to propagate, particularly where more than one species is grown. It gives big plants quickly and only a few stems per division are needed if a large number of plants are required as long as there is sufficient root. I tend to use ‘long toms’ to pot them as they have a good depth and are suitably narrow. Although the prospect of a chance hybrid is exciting from seed raised plants, division is essential to produce progeny genetically identical to the parent which is important for any sort of conservation. It can be the case that plants offered as a species are actually a hybrid, which is how original entities of any sort become lost to cultivation. If wild origin seed, as I was lucky to have from the Crimea, is not available then care does need to be taken if pure species are needed.