Thursday, 21 July 2011

Kew's Royal Mallow (one of the Gay Hyères Tree Mallows)


Lavatera is called the Tree Mallow, or sometimes Royal Mallow. The cultivar I’m featuring today has a Royal Botanic Gardens Kew pedigree so the second common name works for me.

Mallow is a common addition to the vernacular names of plants in the family Malvaceae, also known as the Mallow Family. That well known member of the family, Hibiscus, is sometimes called the Rose Mallow, another name applied occasionallly to Lavatera.


Lavatera x clementii ‘Kew Rose’ doesn’t have its own common name as far as I know, so let’s call it the Kew Royal Mallow – Kew Rose as a common name is all too confusing.

Lavatera x clementii is a collection of hybrids (and backcrosses) between two European species, Lavatera olbia and Lavatera thuringiaca. According to Stewart Hinsley – whose Malvaceae pages are a rich source of lavatera lore – in the UK, both species are simply called Lavatera. For completeness though Stewart says that Hyères Tree Mallow has been used for Lavatera olbia (Stewart says ‘Olbiam is the Latin name for Hyères’), and the charming Gay Mallow has been applied to Lavatera thuringiaca. So make of that what you will, as I have in the title above...

Most flowers fall off without producing fruit, but occasionally viable seed is formed. 'Kew Rose' was a seedling raised from x clementii 'Rosea' and is very similar to that cultivar which also has pink-mauve flowers. According to Stewart, ‘Kew Rose’ is a more robust plant, growing up to 4 metres high.

Again according to Stewart, differences between ‘Rosea’ and ‘Kew Rose’ are subtle but generally flowers, leaves, and stem hairs are all larger on ‘Kew Rose’ and the leaves are ‘more distinctly lobed and toothed’.


The specimen of Kew Royal Mallow illustrated above is in a display collection of plants named after, or for, Royal Botanic Gardens Kew. There are at least 20 hybrids or cultivars bearing the word 'Kew', and many of them are growing in this border between the Main Gate and the Duke's Garden (just before you get to the propped up Stone Pine).

In this case Brian Halliwell - previously head of the Alpine and Herbaceous Section at Kew and retired for the last 25 years - selected the variant of 'Rosea' and named it after his workplace. Current Decorative Manager in Hardy Displays at Kew, Dave Davies, says that during Halliwell's time the 'Duke's Garden' (behind the wall, just further on from the Stone Pine) was very much a plantsman's garden, with new selections on display. The Kew Royal Mallow was lost for some time but when rediscovered it was a welcome addition to the Kew border and for use as a bedding plant.

For the record, Lavatera x clementii 'Kew Rose' received an RHS Award of Merit on 19 July 1988 and three plants were sent to RHS Wisley for a Lavatera trial in April 1994 (thanks Dave! - and note that I would have added these late entries as comments but Blogspot is playing up at the moment and not allowing even me to do this to my own blog...)

We have other lavateras growing at Kew. There are 20-25 species in the genus as a whole, including one native to Australia and a couple from south-western USA. The rest are mostly in Europe through to central Asia. The genus was named by Carl Linnaeus after a sixteenth century Swiss doctor and naturalist, J. R. Lavater, and possibly his brother.

Most x clementii cultivars are shrubs, but Stewart says they can be ‘functionally herbaceous’ in harsher climates. Another you can see in flower in Kew at the moment is Lavatera x clementii 'Barnsley'. We are using this one as an annual in the summer Palm House Partierre, planted out last month and being weeded as we ‘speak’.

The Partierre has lots of pink (or whitish pink in the case of the Lavatera) and grey, with a few splashes of other rather vivid reds and oranges. A little mallow, but not so mellow.

Images: these are some pictures of Lavatera x clementii taken last week by the Director (CEO and Chief Scientist) of Kew, Steve Hopper. They do it justice!

And thanks as always to Simon Goodwin, my remote editor, for picking up a few howlers in the first version...

Postscipt: Martin Cheek from RBG Kew has provided me with some further information on Lavatara and this hybrid/cultivar....

When the new cultivar was being registered Martin was aked to check if the species name under which it was known was correct. At the time it was universally known as L.olbia rosea but Martin found it was closer to L. thuringiaca and wrote an article in the Garden in the late 1980s. Martin says "There was a great deal of interest in the thing and in various cultivars that then came to light, foremost being Barnsley. However the material did have a few unusual charcteristics for that species, such as a high level of sterility, and eventually I was persuaded that it was a hybrid between the two species and I named it x clementii after Eric Clement of BSBI who had listed it as an alien and raised the subject again.


Martin also notes that 'former Linnean limits' between Malva and Lavatera were artificial (epicalyx lobes free or not) and so have been redrawn with molecular support, and that this plant is now Malva x clementii .

Martin also says "the vigour and sterility of this plant probably derive from its (hypothesised) hybrid origin. These features are not seen in related "straight" species. Basically it does not stop flowering until its stems are frosted."

He also corrects my use of the term 'tree mallows', which are Lavatera arborea, not this plant.

Martin finishes with some general comments: "Most european Malvaceae s.s. are known as Mallow in the UK, best known is Althaea officinalis the marsh mallow, roots formerly used to make the sweets of that name now synthesised artificially. ['Lavatera' species are] pollinated mainly by bees and are very very popular in gardens the last 20 years since grows easily from cuttings and produces lots of big pink flowers all summer.

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