Sunday, 17 February 2013

South African Cabbage Trees tolerating centuries of drought in Australian botanic gardens



I'm sure I'd noticed before the Cabbage Tree (Cussonia) outside my old office at the Royal Botanic Garden in Sydney, but it was a pleasant surprise to (re)discover it on my visit there a week or so ago. I was even more pleased to discover first one in the yard of the lodge I'm staying in temporarily at Melbourne's Royal Botanic Gardens and then another rather larger one well within the botanic gardens. 

The species of Cabbage Tree in Sydney is labelled Cussonia paniculata, the one in Melbourne Cussonia spicata. Returning from a walk to the far side of the botanic garden tonight I found another specimen, this time with the same species name as the one I saw in Sydney. 

Here are some more pictures of Cussonia paniculata from Sydney, including one of a flower and perhaps the only pollinator that could love such a flower.


This is the one in Melbourne next to a casually addressed Director on holidays:


So what are these strange and arresting plants? They are in the family Araliaceae - along with ivy and various of the things called Umbrella Trees - and there are about 25 different species. It's their chunkiness and large umbrella-like leaves that make them stand out from the botanical crowd.

The Melbourne specimen of Cussonia paniculata seems to have differently incised leaves to the one in Sydney – they are more what I would call ‘pinnate’, like many ferns. The Sydney one, from memory and my pictures, had fewer segments with saw-shaped edges.

This may be seasonal or age-of-plant variation but my favourite website for African plants, Plantzafrica, mentions two varieties of Cussonia paniculata: the more commonly grown variety sinuata having deeply lobed leaves. I don’t have access at the moment to any technical literature to check this, or indeed to check if the species identifications are correct in the first place. 

Adding to this uncertainty, the plant labelled Cussonia spicata here in Melbourne looks very like the Cussonia paniculata from Sydney. These are pictures of two different specimens in Melbourne, but both clearly the same species. Down here, we seem to call it Cussonia spicata.


Native to tropical and southern Africa, and nearby islands, Cussonia species don’t  mind dry conditions so it suits the planting ethos of most botanic gardens around Australia today.

In fact this has been the ethos of the Melbourne botanic gardens right back to its first curators John Arthur and John Dallachy (1846 to 1857), and first directors Ferdinand Mueller and William Guilfoyle (1857-1909). They all tested the Australian flora to find drought-tolerant gardens plants: Mueller, for example, trialled Blue Gum (Eucalyptus globulus) avenues when the botanic gardens was under his control.

Exotic succulents and other South African plants were early introductions into Melbourne. The largest Cussonia in the Melbourne botanic gardens looks like it might have been a Mueller or Guilfoyle planting. Or indeed both: Guilfoyle famously moved lots of Mueller’s trees to new locations.

I have no doubt there are more of these two Cussonia species in both botanic gardens, and other species, but it's always nice to (re)discover something as distinctive and odd as these South African trees. It might also be nice one day to confirm their identities and get Sydney and Melbourne in sync. Or maybe its just that I'm adjusting to the Australian summer and not taking in the subtle details of the plants yet.

9 comments:

Mary Murphy said...

Hi, I'm sorry to trouble you but I'm also a cussonia fan and my C. paniculata, which I've had growing in my garden in suburban Melb for 5 yrs is now in flower for the first time and has completely changed its form. The plant looks so depleted and is obviously putting all its energy into the flower. I don't know whether I should simply lop the flower off in an effort to get the plant back to its original beautiful upright bushy form.

Tim Entwisle said...

The ones in the Royal Botanic Gardens flower regularly and seem to kick back to life. I wonder if the hot weather is also taking a toll on your plant. I'm sure you are, but good deep watering every few days should help. It might help to lop off the flowers at some stage just to reduce weight. However...I'm not an expert on growing them so I'll see if I can get one of our staff to give me some further advice - I'll post it here if and when I get it! Good luck with this fascinating plant.

Tim Entwisle said...

Not much more advice I can give after consulting with our experts. They think, like me, that it's more likely to be a result of the recent heat - our young Cussonias in the Gardens have shown signs of stress. The advice generally is it's never a good idea to prune anything with more extreme heat on the way. Hope this helps.

Anonymous said...

Hi I have had the tree for about 10 years now ,In Melbourne Australia.

The tree can loose all leaves prior to he flowering.
I see with my example that flowering takes two years to complete.
My observations
Stage 1 the tree grows the flower head trunks,This is the stage were main leaves start dropping,
Stage 2 The tree re sprouts new branches with fast new leave growth.
Stage 3 The flower head trunks now produce flower stems ,flower and then seed.

Tim Entwisle said...

Thanks for those observations. It does have a rather odd growth habit and process!

Papagodesign said...

I have been looking at the discussion of paniculata vs spicata and the confusion found online. Looking at wikipaedia, which is not an authority on many issues, I notice that the two species have distinctively different leaf anatomy. Now if someone could decide which structure belongs to which plant, then we could lay the confusion to rest.

here's a link to a Zim site http://www.zimbabweflora.co.zw/speciesdata/species.php?species_id=142930
and another from SANBI http://pza.sanbi.org/cussonia-paniculata

I have 3 plants purchased as paniculata and would love to know, what I really have in my pots. One seems to be a paniculata. The other two are very small and I am hedging my bets. They were all purchased as paniculatas.

What are your thoughts?

Tim Entwisle said...

It's a difficult one. After writing that post I didn't feel at all confident about how to distinguish the species. Everything I was able to find is provided above I'm afraid - I'm still not sure which species we have.

There are also, apparently, the two subspecies of paniculata, as outlined here: http://www.plantzafrica.com/plantcd/cussoniapan.htm. You might be able to get more information about the two species by comparing this page with the one on spicata (http://www.plantzafrica.com/plantcd/cussonspic.htm) I like the Plants of Africa site and it seems to be very reliable.

Sorry I can't help more. Best wishes, Tim

Papagodesign said...

Hi Tim,

Thank you so much for your response. I've only just stumbled upon it just now. I can now see that all three of my plants are
C. paniculatas. The plant outside has distinctive silvery foliage, the smaller ones indoors are much darker, but same shape foliage.

I obtained 2 plants at collector's corner Gardenworld and the one outside at Yamina Collectors nursery with compound lobed leaves like the subsp. sinuata here http://maree-clarkson.blogspot.com.au/2014/03/kiepersol-cabbage-tree-cussonia.html I have since obtained a C spicata from Roraima nursery, and it has the same foliage structure as the trees in the botanical garden, the individual leaflets being segmented again. But they don't look like the spicata in the above article. (My spicata has sappy green foliage and it needs to be moved into shade, as they are lightening rapidly in full sun.)

These are just my observations based on the labels attached to the plants I purchased and the specimens seen in the botanical garden. Until someone has a closer look at all the anatomical features we will most likely not be any wiser. Hopefully mine will flower at some time in the future.

Happy Holidays,
Sabine

Tim Entwisle said...

Thanks Sabine. Enjoy the continuing discovery! Tim