Tibouchina ‘Blue Moon’

[David F]

Michael, no Tibouchina species are drought resistant in a long Mediterranean climate dry season. There are species that in habitat deal with a drier winter season, but the species in the trade all come from year-round rainfall habitat. It’s not reasonable to expect these to do well on a limited water regimen.

[RobSta]

I've just bought one of these 'Blue Moon', in the hope that it has urvilleana 'blood'. Does anyone have any experience of the cold hardiness of this cultivar?

[Chad]

Welcome to the board Rob.

I can't find a reference to this variety having any frost hardiness in the UK sense of frost.

It seems to have a quoted lower limit of 40F [+4.4C] which would be a light radiation frost.

And that is for a 'one off' temperature, not the UK's prolonged seasonal chill.

Even in Penzance that would need to 'come in' for the winter.

Chad

[RobSta]

Thank you Chad. I'm hoping it has a similar hardiness to urvilleana. There's one way to find out! In the meantime I'll be growing it on, indoors.

[Chad]

I am told that Pleroma urvilleanum [Tibouchina urvilleana] can't be found in UK cultivation.

It has relatively small flowers and we all grow the huge, and intensely purple, flowered Pleroma 'Edwardsii' which is an antipodean hybrid of uncertain ancestry. This is the plant grown outside in Mousehole, Trewidden and here, although here it was cut to the ground in the winter without the polytunnel [hoop house] for protection. It is flowering here now.

Chad

ps.

In this thread Charlie seems to suggest that he grows both urvilleanum and 'Edwardsii', if so Charlie, I know a taxonomist who would be excited to see the urvilleanum.

[charlie]

Had straight urvilleanum first , was then given Edwardsii but I can see very little difference, the flowers of the latter are slightly larger but as both seed quite freely I suspect its just seedling variation. - I must get around to removing one of them from the web site!!

I was intrigued in Dominack's Mousehole garden to see his Tibouchina paratropica has pink flowers where as mine is white, again these seed freely so I suspect they are different forms of the same species.

Good luck with Blue Moon Rob

[David F]

Michael, Tibouchina definitely need irrigation during the dry season and could not be expected to survive an extended dry season without supplemental irrigation. They don’t like dry heat or hot dry wind either. That said, I was surprised to see thriving plants for sale at nurseries in Todos Santos in Baja California Sur with a tropical desert climate at latitude 17°N. They must be planted in bright or dappled shade with wind protection and very well watered to thrive there.

[RobSta]

Thanks for clearing that name up, Chad. Pleroma is easy enough to remember!

Thank you also Charlie, I hope the Pleroma 'Blue Moon' does well so that I can share out cuttings in future :)

[David F]

Charlie, I’m quite surprised you get viable seed on your Tibouchina urvilleana, I’ve never seen them set viable seed here in California. While I generally trust Chad’s discourses on plant genealogy, in this case I highly doubt the large flowered form in the trade is any sort of selected cultivar, it does not make sense coming from Australia here in California. I’ve never seen any sold as ‘Edwardsii’ here.

In a Mediterranean climate such as ours, Tibouchina ‘Blue Moon’ is hardy to light frost at -1°C at least, and sees at least a 6-8 week period of nightly lows around 3-5°C in winter, but it does typically warm back up to 10-12°C in the daytime. One thing I have noticed is the seasonality of bloom period compared to Tibouchina urvilleana, which keeps blooming year round. The T. ‘Blue Moon’ seems limited to late summer/early autumn bloom, and my plant is through for the year. It’s also a much leggier grower, more like T. urvilleana than T. organensis which typically has shorter compact internodes, even when not grown in full sun.

[Chad]

While I generally trust Chad’s discourses on plant genealogy, in this case I highly doubt the large flowered form in the trade is any sort of selected cultivar, it does not make sense coming from Australia here in California. I’ve never seen any sold as ‘Edwardsii’ here.

I would always doubt my musings.

On this occasion though they are not mine.

A now retired professional taxonomist has been trying to sort out the 'Tibouchina' in UK trade, and I'm quoting him.  I haven't asked his permission, so I shan't name him here. 

He points out;  The Tibouchina in the Mousehole garden had flowers over 10-11 cm in diameter, whereas the species (T. urvilleana) has flowers 5-6cm across.

It is his view that the old hybrid made it back from the antipodes and in The UK has displaced the species in cultivation.

BUT, 'Edwardsii' as grown in Australia, is said to be sterile.

I haven't heard him discuss North American plants. 

For what it is worth, my observational taxonomic skills can't get me to genus level in this familly!

Chad