18 responses |
Kath starts with ... I can only imagine the degree of frosts around the country in the past few days, here at the nursery in Kyogle we have had our coldest morning in 30 years this morning. It was incredible to see the results of our frost protection and the damage that an extra degree can do to plants. Our sprinklers come on when the air temperature reaches 0 degrees, this was at 11.30 pm last night so by sunrise there was a thick coating of ice over everything. The ice prevents the cells inside the plant from freezing and therefore prevents damage by the frost.
| About the Author Kath Cawongla 19th July 2007 2:53pm #UserID: 2 Posts: 363 View All Kath's Edible Fruit Trees |
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| About the Author Emma Elermore Vale 19th July 2007 10:52pm #UserID: 150 Posts: 8 View All Emma's Edible Fruit Trees |
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| About the Author Dekka Newcastle 19th July 2007 11:31pm #UserID: 102 Posts: 219 View All Dekka's Edible Fruit Trees |
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Kath says... Here are a couple of before and after shots showing how the ice works. It is latent heat vaporisation that does the trick and I would need my brains trust to help me explain how this works, unless there is someone else out there who can help me out. As the water freezes on the surface of the plant it heats up and creates a buffer from the frost which prevents the cells inside the plant being damaged. The sprinklers stay on all night so by the morning there is a thick layer of ice covering the plants. As it melts the plants do not suffer from internal damage and as you can see these young seedlings do not look as though they have been through a -4 degrees frost. The ice shots were taken this morning at 7.30am, the second shots at 10am once the ice had melted.
| About the Author Kath Cawongla 20th July 2007 10:47am #UserID: 2 Posts: 363 View All Kath's Edible Fruit Trees |
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Correy says... I love those photos. What happens is when you sprinkle water on the plant ice forms as can be seen in the pics. But when new water goes onto the plants the original ice that has formed around the plants releases heat of up to 10 degrees which protects the plant. Maybe someone could help me out with this explanation. Here are some more photos.
| About the Author Correy Woolloongabba, Qld 20th July 2007 11:12am #UserID: 3 Posts: 493 View All Correy's Edible Fruit Trees |
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| About the Author Melissa2 Luddenham 21st July 2007 3:04pm #UserID: 108 Posts: 24 View All Melissa2's Edible Fruit Trees |
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Dekka says... I did some reading and learned that the application of water has two beneficial effects regarding frost protection. 1. The drier the air becomes then more heat is lost into the atmosphere, so humidifying the air reduces the amount of heat radiated away and the severity of the frost. 2. The constant application of water to plants maintains the surface temperature around zero-ish degrees which is generally more tolerable and less damaging than if it continued to drop to several degrees below zero. | About the Author Dekka Newcastle 21st July 2007 8:57pm #UserID: 102 Posts: 219 View All Dekka's Edible Fruit Trees |
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Emma says... im thinking it might also have something to do with the slow formation of the ice crystals of the water within the leaves. From vague memory the slow freeze crystals are differently shaped and therefore are less likely to rupture the cells of the plant? all i know is the reason you cant freeze lettuce is cos the ice crystals rupture the cell walls destroying the crisp structure of the leaf :D -em | About the Author Emma Elermore Vale 21st July 2007 11:08pm #UserID: 150 Posts: 8 View All Emma's Edible Fruit Trees |
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Tony says... Your explanation is basically correct, as the water freezes heat is actually released as the crystalline structure of water ice contains less energy than the liquid state, (even at the same temperature) where the molecules are actually closer together and hydrogen-bonding between the water molecules gives a higher energy state. This is the opposite of most substances but is why water ice floats. The opposite happens as ice melts, it actually takes up a lot of energy to convert water back to the liquid state before the temperature rises at all - very good for cooling drinks. In a similar way the turning of water to gas rather than liquid takes more heat than raising the temperature from zero to 100 degrees in the first place. Evaporative cooling uses this principle. This property of water is unusual, but not unique, ammonia will also behave this way though at a much lower temperature, which makes it the very best refrigerant of all (apart from its toxicity and highly reactive and corrosive nature). This property of water is a major factor in the whole water cycle and weather of the planet. PS. We have had some severe hail and prolonged low temperatures which have done a lot of damage to some of the tropical plants I have been trying to grow, but because of our extreme coastal position and slope we have not had a frost or indeed even a temperature below 2 degrees. I think frost is less of a factor here than lack of any warm temperatures for 4 months in a row. No one seems to have a measure of this factor for warm climate plants, though we do have enough chilling to grow cherries, stone fruit, cox apples, etc with ease. Can anyone develop a maximum chill factor index for tropical and subtropical fruit? | About the Author anthonymiceli1 11th August 2007 11:20am #UserID: 78 Posts: 9 View All anthonymiceli1's Edible Fruit Trees |
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| About the Author anthonymiceli1 11th August 2007 11:25am #UserID: 78 Posts: 9 View All anthonymiceli1's Edible Fruit Trees |
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| About the Author Emma Elermore Vale 12th August 2007 10:45pm #UserID: 150 Posts: 8 View All Emma's Edible Fruit Trees |
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Chris Bourke says... RE: the big freeze....At Tamborine Village near the base of Tamborine Mountain, we had a very cold two days in July....around -4 degrees. Just like at Kyogle, it is the coldest I have recorded in 20+ years. Most of the citrus trees I have stood it fairly well. In particular, practically all of the finger limes I purchased from Daley's Nursery generally came through without ill effect. Some will be turning three years old this summer, and are a mass of flowers (September). The one selection that had "quite a touch up" was the yellow-green cutting grown variety. It may be true that the other selections budded to Troyer Citrange stock have had some degree of cold tolerance imparted to them. Of 30 other finger limes selected from the high country around Kyogle, 15 were killed back to the bud union. They were planted out in July and were not fully dormant when the big frost hit. This I think is a lesson in growing these native citrus in areas prone to the occasional big freeze....if they are dormant and established, they will generally escape damage. All is not lost, I will rebud them in early summer. Regards, Chris Bourke | About the Author Chris Bourke Tamborine Village 11th September 2007 8:22pm #UserID: 299 Posts: 1 View All Chris Bourke's Edible Fruit Trees |
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Kath says... This is very interesting Chris, we also found out that the native finger limes are much hardier than we expected. We had -7 degrees here and they are fine, a few of the varieties died back a little but nothing to worry about they are now covered in new shoots and looking gorgeous. The one in the orchard did not even look as if it had been frosted while everything around it suffered. | About the Author Kath Cawongla 12th September 2007 2:46pm #UserID: 2 Posts: 363 View All Kath's Edible Fruit Trees |
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Rev says... out here in tabulam we had a few nights at teh same time -4,-5 and -6 Most citrus were unhurt if a touch scalded and all are on trifoliata or flying dragon the arnold blood and buddha hand citron got cut back - i was suprised about the orange unhurt list is : minneola, ryan navel, washington navel, valencia, mandarins, pink ice fingerlime, tahitian lime, kaffir lime banana cut back to rootstock (as are every year)but looks great now tassie berry got burned badly and some died (ugni) riberry and magenta cherry, davidsons plum - all dead sandpaper fig reshoots in spring acerola was killed stone dead andean walnut cut to main trunk killed outright down the road were brazil cherry, pachira insignis, and bilimbi, passionfruit - of course biggest suprise was indeed the jaboticabas which seemed untouched while trees next to them melted A hybrid seedling macadamia was unhurt. even its seedlings only got scorched and reshot in spring | About the Author RevNQ1 Tabulam 19th November 2007 12:50am #UserID: 441 Posts: 31 View All RevNQ1's Edible Fruit Trees |
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John A says... I read with much interest the above comments. We live in Hahndorf, Adelaide Hills, where it can get to -7 or so some winter nights. We are going away for a while, and it has been suggested we cover frost susceptible plants with black weedmat over a wire frame. I understand the black will absorb heat during the day, and the cover will protect the plant from the dew, so there won't be any moisture to freeze when the temp drops overnight. It is neither practical (or legal) to spray water on plants. Has anyone had any experience with the weedmat or similar? | About the Author John A Australia 28th May 2009 10:04am #UserID: 2396 Posts: 1 View All John A's Edible Fruit Trees |
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amanda says... Just for interest/records - we have had a 2 nites of frost and -1.5 oC lowest and so far the young (uncovered) sub tropicals are fine here... (starfruit, kwai muk, longon, lychee, white sapote, mangoes, grumichama, lychee, jaboticaba, avocado, sapodilla, tamarillo, passionfruit) I threw a bit of frost fabric over the top of the jackfruit - and it's ok too (it's under some mature trees - and frost doesn't form on the ground there tho) | About the Author amanda19 Leschenault (150km south of Perth) 10th July 2013 10:53am #UserID: 2309 Posts: 4607 View All amanda19's Edible Fruit Trees |
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| About the Author Theposterformerlyknownas Brisbane 10th July 2013 1:13pm #UserID: 3270 Posts: 1552 View All Theposterformerlyknownas's Edible Fruit Trees |
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amanda says... That's good to hear BJ - this is our first winter with frost - and these trees were in a fairly warmer climate this time last year in Geraldton (700kms north roughly - and - semi arid versus warm temperate)... I am really pleased so far... My gut feeling is that the starfruits may have been happier under the protection of the big trees tho... They just seem fragile to me..? | About the Author amanda19 Leschenault (150km south of Perth) 10th July 2013 8:22pm #UserID: 2309 Posts: 4607 View All amanda19's Edible Fruit Trees |
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