Notes on the Canary Island lavenders

Tim Upson and Stephen Jury
Department of Botany, School of Plant Sciences, University of Reading, Whiteknights, Reading, PO Box 221, Berkshire, RG6 6AS

From The Lavender Bag 5 (May 1996)

Following a recent visit to the Canary Islands by Tim Upson (Tenerife, February 1996) and subsequent study of herbarium material and literature, the following notes detail some of the findings and observations we have made to date. We hope this will help clarify some of the taxonomy of these lavenders, which in some instances we have found to be confused. These notes precede a more detailed account and revision which is at present in preparation.

There are four species native to the Canary Islands: L. pinnata L. fil., L. buchii Webb & Berthelot , L. minutolii Bolle and L. canariensis Miller. Two other species appear in the literature, L. dentata L. and L. stoechas L. but there is no doubt that these taxa have been introduced. In fact, L. dentata was encountered on several occasions in gardens and civic plantings around the island of Tenerife during the recent trip. The following notes are restricted to the native species.

Lavandula canariensis
This is by far the most common and widespread species, being recorded from all the islands. Some authors, e.g. Kuntze (1891: 522) and Pitard & Prost (1908: 299) have sunk this taxa into L. multifida. Whilst there may be a close relationship, it is clearly a distinct species on account of leaf characters, calyx shape and colour, bracts shape and length and the stem indumentum. There is a great deal of variation in these characters between populations throughout the islands and as such we accept it as a variable species. On occasions leaf shape and dissection can resemble that of L. minutolii, but careful examination of other characters will usually distinguish them.

Much has been mentioned of hybridisation with other species, especially within cultivated stock. Experience from Tenerife showed very little hybridisation occurs in the wild, indeed mixed populations of lavenders were rarely encountered. A single plant, a possible hybrid with L. buchii, was found at only one site on Tenerife and only two other herbarium specimens have been seen that may also be of hybrid origin. There were certainly not the large hybrid swarms that occur in other Canary Island genera such as Echium. Hybridisation may well be more common in cultivation and this aspect may warrant further investigation.

We cannot leave this species without commenting on the vividness of its blue/mauve flowers. Although no doubt enhanced by the clear sunny environment of the Canaries, plants in full flower are a spectacular sight, often visible from a distance. It is evidently worthy of cultivation, best treated as a half hardy perennial in the UK, requiring frost protection over the winter. We have found it easy to cultivate in the glasshouses at Reading, with plants benefiting from standing outside during the summer.

Lavandula pinnata and L. buchii
There has been much discussion and confusion over the taxonomic status and distributions of these two species, but this is one problem that we hope to have resolved. Lavandula buchii has been treated as a subspecies of L. pinnata in many accounts. We have found that these two taxa can be clearly distinguished on a number of characters, shown in the table below, and they should be treated as distinct species. They can be clearly distinguished from the other species by the densely packed hairs on all parts of the plant, and especially the leaves which gives them a distinct grey to silver/grey colour.

It is evident from our study that many specimens of L. buchii have been frequently misidentified as L. pinnata or not recognised as subspecies buchii. However, as plants of L. buchii can resemble L. pinnata at first glance it is easy to see why such confusion has occurred. The large bracts and distinctly obovate leaf lobes of L. pinnata are so distinct, that these species can be clearly distinguished, once one is familiar with these characteristics.

This taxonomic confusion now casts a new light on the distribution of these two species. The true L. pinnata is frequently listed as being native to Tenerife e.g. Hansen & Sunding (1993), and so we believed until visiting site upon site and finding only L. buchii. Examination of material at The University of Reading, The Royal Botanic Gardens, Kew, The Natural History Museum and loans from foreign herbaria all confirmed this problem of misidentification. In the light of this, L. buchii is endemic to Tenerife and L. pinnata to Gran Canaria and Lanzarote (and also Madeira). There is a literature reference to L. pinnata occurring on Fuerteventura but as yet we have not seen any specimens to confirm this.

Variation in L. buchii
Lavandula buchii is native to Tenerife, but there is more to this story. A study on the variation of this species by León & Wildpret (1987) recognised three varieties: var. buchii (the type and thus typical variant), var. gracile León and var. tolpidifolia (Svent.) León. Our studies to date would seem to support the recognition of these taxa. The variety L. buchii var. buchii is distinguished by its short flower spikes about 4-6 cm long, which are branched two to three times and clustered at the end of the peduncle. The leaf lobes tend to be linear to slightly obovate and the terminal lobe rhomboid in shape. This variety is recorded mainly from the Anaga Peninsula in the north of Tenerife, but it also occurs in the south.

In contrast, var. gracile is a larger plant with longer flower spikes, upto 10cm. Each pair of flowers tends to be more widely spaced up the spikes, which is usually branched once or twice. The spikes are not clustered at the end of the peduncle as in var. buchii. The varietal name 'gracile' actually means slender which describes the inflorescence well. The leaf lobes also tend to be linear in shape and thus much thinner in width. This variety is restricted to the southern part of Tenerife.

The variety tolpidifolia is much more restricted in its range and is known from one Barranco in the south of Tenerife. It is easily distinguished from the other varieties by its leaves, which are lanceolate in outline with irregular shallow lobes, in contrast to deeply dissected pinnatisect leaves usual in the species. We have not seen this plant and doubt if it is in cultivation.

We believe both L. buchii var. buchii and var. gracile are in cultivation in the UK. Both have proved easy to grow at Reading, the leaves being particularly attractive, although the flowers do not quite have the bright vivid colours of the other Canarian taxa.

L. minutolii
This attractive species is distinguished by its leaf shape being lanceolate to ovate with deep very regular pinnatisect divisions. Other aspects of its appearance indicate a close relationship with L. canariensis. Its stronghold appears to be the island of Gran Canaria, but it is also found in the southern part of Tenerife. The populations here have been recognised as a distinct variety L. minutolii var. tenuipinna (Svent.) León. They certainly do seem to be different, varying in the leaf shape and dissection from those populations on Gran Canaria.

This is certainly a very attractive species, which seems less widely cultivated in the UK than any of the other Canarian lavenders according to The RHS Plant Finder, Lord (1995: 359-360). Again there seems few problems in cultivating this plant and it deserves to be more widely grown.

We hope these brief notes may help to clarify certain aspects of the taxonomy of the Canary Island lavenders. They are certainly amongst some of the most attractive species in the genus and well worth a place in our gardens.

References

• Hansen, A. & Sunding P. Flora of Macaronesia. Checklist of vascular plants. 4 revised edition. Sommerfeltia 17: 138.
• Kuntze, O. (1891). Revisio Generum Plantarum. Leipzig.
• Leon-Arencibia, M.C. & Wildpret de la Torre, W. (1987). Taxones infraespecíficos de Lavandula buchii (Lamiaceae). Vieraea 17: 353-360.
• Lord, T. (1995). The RHS Plant Finder: Devised and compiled by C. Philip; edited by T. Lord. London.
• Pitard, C.J.M. & Prost L. (1908). Les Iles Canaries, Flore de L'Archipelago. Paris.

[Dr Upson is now Superintendent of the Cambridge University Botanic Gardens in the UK]