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Grevillea robusta leaking resin...


Kostas

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Hello :)

A couple of months ago,my Grevillea robusta started leaking resin from its lower trunk. There is no *visible* damage to the bark there and the bark color and everything seems normal in the area. The tree seems strong overall,it is throwing down a lot of leafs now but i think that is normal for this species and they usually throw a lot of leafs prior to their flowering and putting new growth. New growth has started on the branches,strong.

The thick resinous liquid leaking was yellowish when i first saw it at the end of December,then it was all washed away and not to be seen during a relatively dry period,and now,last weekend i was in Pyrgos again and checked the tree,copious amounts of this liquid have been excreted and seems to have change from yellowish to white(or it may be that oxidation gets it yellowed but this time it was very fresh and continually produced). I think i see some linkage with the rains and that after heavy rains,its excreted in good amounts while it mostly ceases after drier weather(less water in the soil).

Here are a couple pictures from 2 weeks ago

7F9E2306-4A6A-46B9-A5B3-E58E35C8163C_zps

C41C1508-CD22-41C6-9510-535F882DD727_zps

And from last weekend

IMG_2516a_zps051b64ba.jpg

IMG_2515a_zps28ac2906.jpg

Is this normal for this species? I suspected a borer of some kind but cant find any visible hole and with so much resin,i would think it would suffocate there. I also suspected fungus but the tree seems to be doing well and,well,if its fungus,there is nothing i can do anyway...But the resin is a nice,light color and very thick,which to me indicates healthy resin.

What do you think? Is this tree in trouble or is it natural for this species to excrete resin when super happy or when water is coming out its ears as we would say(1200mm of rain and water table at around 40-60cm below the soil surface)?

Thank you very much in advance! :)

''To try,is to risk failure.......To not try,is to guarantee it''

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Grevillea robusta thrives in the much drier town of Nauplion as public trees (without any goo flowing), so I think, as you have already guessed, it is not normal but rather a sign of overwatering. Whether it is already a disease or just a mechanical damage, I think it is advisable to seal off the 'wound'. Scrape the bark above exit point and apply a paste made of water and KoCide powder or cooper-lime powder. I have managed this way to save several fruiting trees (appricot, almond and other trees) for ever.

Edited by Phoenikakias
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Grevillea robusta also thrive in the town of Pyrgos but none of the town planted trees grows anywhere as fast as mine. The most impressive one i have seen is growing out of a small lot in front of a building,the best example of this species i have ever seen at 15-20m tall.

Mine is close to 9m tall now in just 5years from a 2m tall, 1,5cm thick trunked sapling and flowered for the first time last year,setting many seedpods. Its a very happy tree but with the rains we get,anything can rot. Half of this tree blew down last winter from hurricane force winds(hurricanes formed just outside Pyrgos bringing down huge trees and breaking and uprooting large olives),breaking at its main fork. The wound is healing nicely,way better than i expected and quite fast but it still needs a few years till it fully closes. The exposed wood appears reasonably ok and the bark is closing fast around it.

IMG_2428a_zps5401ab37.jpg

IMG_2427a_zps18ee9115.jpg

As you said,Nauplion is way drier. Mine seems to stop producing it during drier weather(while the soil is still very moist,just less so than after heavy rains. Soil is well draining but water always available from the shallow water table and soil moist yearround),so that doesnt mean that this species cannot normally excrete resin when there is an abundance of water. Just like plants dont guttate unless there is an abundance of water. I just have never seen that before and hoped to hear if anyone else from a very rainy region has seen that and how the tree fared after that. If the tree remains fine and healthy and lives a very long life,growing many tens of meters high,then having resin leaking is totally fine with me!

I have read about Grevillea robusta producing resin and that its uses are being evaluated but could not find wether this is spontaneous or only after wounding/problems.

Thank you very much for the treatment suggestion! There is too much resin excretion(tried cleaning the suspected but not visible exit point but within seconds more poured out between the bark fissures) and too much rain for any paste to hold. What did your fruit trees have? This paste should work great to prevent infection but i dont think it(or anything for that matter) could treat any systemic infection or inner wood infections,only very localized ones maybe.

''To try,is to risk failure.......To not try,is to guarantee it''

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As many of the horticultural sites state, we must not confuse pathogenic resin excretion with the normal resin excretion some tree species exhibit following certain environmental conditions,but without causing them any harm. Some trees leak resin to get rid of excess water or due to carbohydrate imbalances,not linked to any pathogen activity.

I see no bark necrosis or discoloration even where the resin comes out,that's why I have been relatively calm about it the 2-3 months I have seen it occurring. An arborist told me that if its leaking great quantities of resin,which mine is(I even see largish insects trapped in the resin,like amber with enclosed insects in formation!),its most likely to be natural for this species than pathogenic,which is linked to slow leakage of relatively small quantity of resin PLUS other adverse effects seen on the tree(bark necrosis or discolorAtion,bad tree health,leaf loss,slow growth). Mine so far so good but wanted to check here as we have some great tropical tree arborists which might provide more insight. Grevillea robusta is an unusual tree for Greece and not one horticulturists here have much experience on.

I am certainly happy and gracious for your advise but I am more inclined to think this is normal than pathogen caused. And I am extremely reluctant to use any chemicals in my garden,I garden solely organically and even organic medications,I seldom to never use them unless totally needed. I rely on the good condition and strength of the plants to help them overcome their problems and just do what I can to change the conditions to their favor and to their enemies dislike. And I also import natural enemies which take care of pests permanently(all but Rhynchophorus and Paysandisia...). Thank you very much again Konstantinos and be sure that if I get sure the resin excretion is from pathogens and curable ones,I will treat it. Till them it's on its own,as it always has been and it's quite efficient at compartmentalizing the damage and healing itself. I like this species! Hope its seeds grow wild in the neighboring empty lots! :)

''To try,is to risk failure.......To not try,is to guarantee it''

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According to the book "Plant Gum Exudates of the World: Sources,Distribution,Properties and Applications",Grevillea robusta also exudes gum naturally:

http://books.google.gr/books?id=HnAnETsS1zsC&pg=PA132&lpg=PA132&dq=grevillea+gum&source=bl&ots=uxeu-dCN-0&sig=Rt-uTb1JiR7R5EnCLYpU-f8pDNE&hl=en&sa=X&ei=s9UYU5vrNoKDtAaF-oDQBg&ved=0CDYQ6AEwBg#v=onepage&q=grevillea%20gum&f=false

Now if mine does it naturally or not,I don't know but it thankfully seems so :)

''To try,is to risk failure.......To not try,is to guarantee it''

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I'd just leave it alone.

Matt Bradford

"Manambe Lavaka"

Spring Valley, CA (8.5 miles inland from San Diego Bay)

10B on the hill (635 ft. elevation)

9B in the canyon (520 ft. elevation)

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I'd just leave it alone.

Agree with Matt here, this is a local native tree for me, also known as "Silky Oak", like all Grevilleas, leave them be, they'll usually fix themselves, never add water or fertiliser to these trees, best grown through neglect by humans.

Happy Gardening

Cheers,

Wal

Queensland, Australia.

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I'd strongly recommend removing all those green, coated wires from the trunk.

SoCal and SoFla; zone varies by location.

'Home is where the heart suitcase is'...

_____

"If, as they say, there truly is no rest for the wicked, how can the Devil's workshop be filled with idle hands?"

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Thank you very much Matty and Wal, that has been my inclination as well seeing it doesnt have visible problems. I generally dont mess with my trees,i just build the soil with organics and mulch and let them fend for themselves and take care of their problems as most strong trees are more than able to.

Wal,your natives are awesome plants and adapt very well to my growing area! Most of my main shade trees to be are from your area,the Grevillea robusta(the only one fast enough to actually cast enough shade for shade plants),Castanospermum australe(3,5-4m after 4years in the ground from young seedling,slow but getting faster each year,no shade yet) and,after last weekend's planting,Stenocarpus sinuatus(two 5m ones! Little to no shade yet of course)!

My Grevillea is in an area getting sprayed daily for the ferns growing underneath it(Dicksonia antarctica) and for the epiphytes on its trunk. The soil is yearound moist but extremely rich and well draining from the mulch and Grevillea's fallen leafs rotting those 5 years. The point of gum exit is not wet by the microsprayers or the very brief run sprinklers. Only heavy rain wets it.

I fertilize the plants beneath it lightly with organic,slow release fert.

fastfeat,

Thank you very much for your concern and advise! :) These are not wires but special tree ties,soft,hollow tubing that expands with the lightest tug. I use it to tie epiphytes on the trunk till they establish themselves and attach well enough to hold not only their weight,but the cats that tend to climb on the trunk and step on them as well...Many of these ties are on the trunk for years and none has made even the slightest mark on it,despite the trunk expanding to twice the diameter it had back then :)

''To try,is to risk failure.......To not try,is to guarantee it''

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However, because all conditions for phytophthora also exist, just better keep a constant eye on the tree and especially watch if more secretion points will be created, if latter occurs it can well be an alarm signal.

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I do will be keeping an eye on it,it's a valuable shade tree to me :) Good thing is,temperatures will be high soon and drier weather is here for awhile :)

''To try,is to risk failure.......To not try,is to guarantee it''

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