The MGS Forum
Plants for mediterranean gardens => Trees and Shrubs => Topic started by: Alisdair on November 17, 2011, 04:13:01 PM
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Anita in Australia has posted an interesting item about grafting the ground-cover desert Grevillea laurifolia (syn. G. gaudichaudii) on to tree-sized G. robusta, in another thread which you can see here (http://www.mgsforum.org/smf/index.php?topic=548.msg3328#msg3328). I'll try to get Anita to post a picture for us.
Has anyone other experience of growing desert grevillea species in mediterranean climates?
The grevillea that we are most familiar with is G. rosmarinifolia, a very rewarding plant in mediterranean conditions, though appreciating at least some water in summer.
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Alisdair,
Believe it or not, very recently, this victim of a 'Chain Saw Massacre' was a beautiful specimen of a Grevillea robusta. Probably a prime example of a very large tree being planted too close to a house. Our neighbours have realised their mistake, but maybe too late, certainly for the tree.
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Important cultural info - http://anpsa.org.au/grev3a.html.
But see also the Grevillea index page - http://anpsa.org.au/greville.html (http://anpsa.org.au/greville.html).
I bought a prostrate Grevillea lanigera (not sure if is a 'desert species') this spring, and managed to kill it by having it where it received irrigation with other plants.
Also, because of toxicity, especially in G. robusta, I have leaned away from Grevillea. I can't remember where I read that now, though there is an article in TMG No.57, p.5.
John,
The pruning leaves a framework that could develop OK, as shoots emerge and develop. I note the pruner has left collars on the side branches (correct) and seems to have made quite clean (not ragged) cuts (correct). So, though the aesthetics could be better, I get a feeling the pruner may have had some experience of pruning (though not necessarily re Grevillea). Elsewhere, I have read that they respond quite well to pruning.
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You're probably right, Mike, but the tree is so close to the house (the photo being taken straight on the perspective doesn't show just how close) that, unfortunately, by the time it begins to regain a decent shape they'll no doubt have to chop it again.
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Hi, I'm away from home at the moment without easy access to photos so I'll point you to a couple of websites that do demonstrate what can be done in the way of grasfting prostrate cultivars onto G.robusta standards.
One of these is http://www.australisplants.com.au/ornapmentals/graftedgrevilleas.htm, the other is http://www.weepers.com.au/about_weeping_grevilleas.html.
In relation to grevilleas I've not seen any allelopathic effects caused by Grevillea species in the garden. I've grown other species right up to the shrub canopy.. At this point other plants struggle to compete with the dense shade created by vigorously growing plants. In the case of G. robusta, while it is a most beautiful tree, with a lovely pyramidal natural habit, and attractive silvery undersides to the leaves which in breezes shift and appear to make the tree sparkle or color shift from deep green to grey with the movement of the leaves, further enhanced by striking yellow flowers in late spring. I would not plant it near any building as it has an extremely aggressive root system that will work its way into water and effluent piping in search of moisture. It is hard to grow anything under G robusta (not the grafted versions which are much more amenable) but the tree in its natural state because of this vigorous root system which produces both shallow feeder roots and deep water seeking roots. G robusta also tends to 'self-mulch' dropping leaves and seedpods nearly continously, creating a deep competition suppressing mulch under the canopy.
I'd suggest that it would have been kinder and more sensible to remove the G robusta pictured rather than prune it in such an idiotic fashion. The robusta is hard to kill and it will survive and within a very short time will replace the growth that's been removed but it will not regain its attractive shape.
The suggestion the Grevilleas respond well to regular pruning applies to the shrubby types and not robusta. The shrubby types will respond well to hard pruning which may be necessary from time to time to reinvigorate leggy shrubs.. But in the main it is better to regularly tip prune to encourage dense growth. Anita
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Most informative, Anita, thanks.
The toxicity I was referring to was re humans rather than other plants.
It is alluded to in the Wiki entry:
"Toxicity and allergic reactions
The flowers and fruit contain toxic hydrogen cyanide.[4] Tridecylresorcinol in G.robusta is responsible for contact dermatitis.[5]
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5. Menz, J., Rossi, R., Taylor, W.C, Wall, L., Contact dermatitis from Grevillea'Robyn Gordon', Contact Dermatitis, Vol. 15, Iss. 3, pp 126-131, Apr 2006"
and
"Severe body rash and allergic dermatitis" (http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0008/112796/garden-plants-poisonous-to-people.pdf (http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0008/112796/garden-plants-poisonous-to-people.pdf))
(Mind you, the same site says of Melia azederach "Nausea, spasms, drowsines then convulsions, death.")
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The toxicity I was referring to was re humans rather than other plants.
It is alluded to in the Wiki entry:
"Toxicity and allergic reactions
The flowers and fruit contain toxic hydrogen cyanide.[4] Tridecylresorcinol in G.robusta is responsible for contact dermatitis.[5]
...
5. Menz, J., Rossi, R., Taylor, W.C, Wall, L., Contact dermatitis from Grevillea'Robyn Gordon', Contact Dermatitis, Vol. 15, Iss. 3, pp 126-131, Apr 2006"
Sorry Mike,
I misunderstood - a number of Australian species are allelopathic (releasing toxins that suppress the growth of other plants) in order to preserve water and nutrients in poor soils and dry climates - so I jumped to that interpretation.
Some grevilleas do cause strong dermatis reactions in some people. The cultivar Robyn Gordon and related hybrids are infamous for this character which causes contact dermatitis and inflammation among susceptible people and in a friend's case, her poodle (the dog lost its hair on back and breeches and was treated for a severe allergic reaction. The treatment didn't seem to help but then they removed a grevillea Robyn Gordon while landscaping the rear garden and the dog improved within weeks.)
Another reaction involved my better half who does not react to grevilleas usually but several years ago developed a terrible recurring rash. A dermatologist identified it as an allergic reaction but we were baffled as to the cause. It was some weeks before we realised that the rash was caused by the logs we were using in the open fire. A friend had cut down a large Grevillea robusta and we were burning the logs. As soon as Peter stopped handling the wood his rash abated. The strangest aspect of the whole episode was that Peter wasn't affected by the foliage of G robusta (or any other grevillea species) but reacted strongly to contact with the timber.
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Thanks again Anita - such first-hand experience is very valuable.
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For Daisy's great pictures of Grevillea robusta flowering, click here (http://www.mgsforum.org/smf/index.php?topic=812.0).
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Can anyone advise me about pruning Grevillea. I want to know the best time to prune and if I can prune down to the hard wood.
I have three. Grevillea johnsonii, G. beadleana and Grevillea x Robyn Gordon. They are getting too big and I need to do something with them this year.
Thanks
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Be very cautious when pruning Grevilleas. Cutting into brown, barky wood is not recommended. Most Australian native plant enthusiasts tip prune regularly and use cutting off finished flower stems as the time to prune a little harder but never down to hard wood.
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Thank you so much...thats really helpful.